Miscarriage
Encyclopedia
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy
at a stage where the embryo
or fetus
is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation
. Miscarriage is the most common complication of early pregnancy.
(since the woman's Last Menstrual Period)—are medically termed early pregnancy loss or chemical pregnancy. Miscarriages that occur after the sixth week LMP are medically termed clinical spontaneous abortion.
In medical (and veterinary) contexts, the technical term "abortion
" refers to any process by which a pregnancy ends with the death and removal or expulsion of the fetus, regardless of whether it is spontaneous or intentionally induced. Many women who have had miscarriages, however, object to the term "abortion" in connection with their experience, because in everyday English the word is strongly associated with induced abortions. In recent years there has been discussion in the medical community about avoiding the use of this term in favor of the less ambiguous term "miscarriage". In 2005 the European Society for Human Reproduction and Embryology (ESHRE) published a paper aiming to facilitate an update and revision of nomenclature used to describe early pregnancy events.
Labour resulting in live birth before the 37th week of pregnancy is termed "premature birth
", even if the infant dies shortly afterward. The limit of viability
at which 50% of fetus
/infant
s survive longterm is around 24 weeks, with moderate or major neurological disability dropping to 50% only by 26 weeks. Although long-term survival has never been reported for infants born from pregnancy shorter than 21 weeks and 5 days, fetuses born as early as the 16th week of pregnancy may sometimes live for some minutes after birth.
A fetus that dies while in the uterus after about the 20–24th week of pregnancy is termed a "stillbirth
"; the precise gestational age definition varies by country. Premature births or stillbirths are not generally considered miscarriages, though usage of the terms and causes of these events may overlap.
Miscarriage of a fetus is also called intrauterine fetal death (IUFT).
Alternatively the following terms are used to describe pregnancies that do not continue:
The following two terms consider wider complications or implications of a miscarriage:
The physical symptoms of a miscarriage vary according to the length of pregnancy:
Miscarriage may also be detected during an ultrasound exam, or through serial human chorionic gonadotropin
(HCG) testing. Women pregnant from ART
methods, and women with a history of miscarriage, may be monitored closely and so detect a miscarriage sooner than women without such monitoring.
Several medical options exist for managing documented nonviable pregnancies that have not been expelled naturally.
For those who do go through a process of grief
, it is often as if a baby had been born but died. How short a time the fetus lived in the womb may not matter for the feeling of loss. From the moment pregnancy is discovered, the parents can start to bond with the embryo or fetus. When the pregnancy turns out not to be viable, dreams, fantasies and plans for the future are roughly disturbed.
Besides the feeling of loss, a lack of understanding by others is often important. People who have not experienced a miscarriage themselves may find it hard to empathize
with what has occurred and how upsetting it may be. This may lead to unrealistic expectations of the parents' recovery. The pregnancy and miscarriage are hardly mentioned any more in conversation, often because the subject is too painful. This can make the woman feel particularly isolated. Inappropriate or insensitive responses from the medical profession can add to the distress and trauma experienced, so in some cases attempts have been made to draw up a standard code of practice.
Interaction with pregnant women and newborn children is often also painful for parents who have experienced miscarriage. Sometimes this makes interaction with friends, acquaintances and family very difficult.
Chromosomal abnormalities are found in more than half of embryos miscarried in the first 13 weeks. A pregnancy with a genetic problem has a 95% probability of ending in miscarriage. Most chromosomal problems happen by chance, have nothing to do with the parents, and are unlikely to recur. Chromosomal problems due to a parent's genes are, however, a possibility. This is more likely to have been the cause in the case of repeated miscarriages, or if one of the parents has a child or other relatives with birth defects. Genetic problems are more likely to occur with older parents; this may account for the higher miscarriage rates observed in older women.
Another cause of early miscarriage may be progesterone
deficiency. Women diagnosed with low progesterone levels in the second half of their menstrual cycle (luteal phase
) may be prescribed progesterone supplements, to be taken for the first trimester of pregnancy. No study has shown that general first-trimester progesterone supplements reduce the risk of threatened miscarriage (when a mother might already be losing her baby), and even the identification of problems with the luteal phase as contributing to miscarriage has been questioned.
, growths in the uterus (fibroids), or cervical problems
. These conditions may also contribute to premature birth
.
One study found that 19% of second trimester losses were caused by problems with the umbilical cord
. Problems with the placenta
may also account for a significant number of later-term miscarriages.
Uncontrolled diabetes greatly increases the risk of miscarriage. Women with controlled diabetes are not at higher risk of miscarriage. Because diabetes may develop during pregnancy (gestational diabetes
), an important part of prenatal care
is to monitor for signs of the disease.
Polycystic ovary syndrome is a risk factor for miscarriage, with 30-50% of pregnancies in women with PCOS being miscarried in the first trimester. Two studies have shown treatment with the drug metformin
to significantly lower the rate of miscarriage in women with PCOS (the metformin-treated groups experienced approximately one-third the miscarriage rates of the control groups). However, a 2006 review of metformin treatment in pregnancy found insufficient evidence of safety and did not recommend routine treatment with the drug.
High blood pressure
during pregnancy, known as preeclampsia, is sometimes caused by an inappropriate immune reaction (paternal tolerance) to the developing fetus, and is associated with the risk of miscarriage. Similarly, women with a history of recurrent miscarriages are at risk of developing preeclampsia.
Severe cases of hypothyroidism
increase the risk of miscarriage. The effect of milder cases of hypothyroidism on miscarriage rates has not been established. The presence of certain immune conditions such as autoimmune disease
s is associated with a greatly increased risk of miscarriage. The presence of anti-thyroid autoantibodies
is associated with an increased risk of miscarriage with an odds ratio
of 3.73 and 95% confidence interval
1.8–7.6.
Certain illnesses (such as rubella
, chlamydia and others) increase the risk of miscarriage.
Tobacco (cigarette) smokers have an increased risk of miscarriage. An increase in miscarriage is also associated with the father being a cigarette smoker. The husband study observed a 4% increased risk for husbands who smoke fewer than 20 cigarettes/day, and an 81% increased risk for husbands who smoke 20 or more cigarettes/day.
Cocaine use increases miscarriage rates. Physical trauma, exposure to environmental toxins, and use of an IUD during the time of conception have also been linked to increased risk of miscarriage.
Antidepressants specially paroxetine
and venlafaxine
can lead to spontaneous abortion.
The age of the mother is a significant risk factor. Miscarriage rates increase steadily with age, with more substantial increases after age 35.
occurs when the body's own immune system acts against itself. Therefore, in the case of an autoimmune-induced miscarriage the woman's body attacks the growing fetus or prevents normal pregnancy progression. Further research has also suggested that autoimmune disease can cause genetic abnormalities in embryos which in turn can lead to miscarriage.
) are associated with a decreased risk of miscarriage. Several mechanisms have been proposed for this relationship, but none are widely agreed on. Because NVP may alter a woman's food intake and other activities during pregnancy, it may be a confounding factor when investigating possible causes of miscarriage.
consumption has also been correlated to miscarriage rates, at least at higher levels of intake. A 2007 study of over 1,000 pregnant women found that women who reported consuming 200 mg or more of caffeine per day experienced a 25% miscarriage rate, compared to 13% among women who reported no caffeine consumption. 200 mg of caffeine is present in 10 oz (300 mL) of coffee or 25 oz (740 mL) of tea. This study controlled for pregnancy-associated nausea and vomiting (NVP or morning sickness): the increased miscarriage rate for heavy caffeine users was seen regardless of how NVP affected the women. About half of the miscarriages had already occurred at the time women were recruited for the study. A second 2007 study of approximately 2,400 pregnant women found that caffeine intake up to 200 mg per day was not associated with increased miscarriage rates (the study did not include women who drank more than 200 mg per day past early pregnancy). A prospective cohort study in 2009 showed no increased risk.
and by the examination of the passed tissue. When looking for microscopic pathologic
symptoms of miscarriage, one looks for the products of conception. Microscopically, these include villi
, trophoblast
, fetal parts, and background gestational changes in the endometrium
. Genetic tests may also be performed to look for abnormal chromosome
arrangements.
. Pain does not strongly correlate with miscarriage, but is a common symptom of ectopic pregnancy. In the case of concerning blood loss, pain, or both, transvaginal ultrasound
is performed. If a viable intrauterine pregnancy is not found with ultrasound, serial βHCG
tests should be performed to rule out ectopic pregnancy, which is a life-threatening situation.
If the bleeding is light, making an appointment to see one's doctor is recommended. If bleeding is heavy, there is considerable pain, or there is a fever, then emergency medical attention is recommended to be sought.
Whilst bed rest
has been advocated in the past to help ensure that the pregnancy might continue, and in one study possibly helped when small subchorionic hematoma had been found on ultrasound scans, the prevailing opinion is that this is of no proven benefit.
No treatment is necessary for a diagnosis of complete abortion (as long as ectopic pregnancy is ruled out). In cases of an incomplete abortion, empty sac, or missed abortion there are three treatment options:
before and during pregnancy reduced the risk of pregnancy losses.
of miscarriage is difficult. Many miscarriages happen very early in the pregnancy, before a woman may know she is pregnant. Treatment of women with miscarriage at home means medical statistics on miscarriage miss many cases. Prospective studies using very sensitive early pregnancy tests have found that 25% of pregnancies are miscarried by the sixth week LMP
(since the woman's Last Menstrual Period). However, other sources reports suggest higher rates. One fact sheet from the University of Ottawa states, "The incidence of spontaneous abortion is estimated to be 50% of all pregnancies, based on the assumption that many pregnancies abort spontaneously with no clinical recognition." The NIH reports, "It is estimated that up to half of all fertilized eggs die and are lost (aborted) spontaneously, usually before the woman knows she is pregnant. Among those women who know they are pregnant, the miscarriage rate is about 15-20%." Clinical miscarriages (those occurring after the sixth week LM) occur in 8% of pregnancies.
The risk of miscarriage decreases sharply after the 10th week LMP, i.e. when the fetal
stage begins. The loss rate between 8.5 weeks LMP and birth is about two percent; loss is “virtually complete by the end of the embryonic period."
The prevalence of miscarriage increases considerably with age of the parents. One study found that pregnancies from men younger than 25 years are 40% less likely to end in miscarriage than pregnancies from men 25–29 years. The same study found that pregnancies from men older than 40 years are 60% more likely to end in miscarriage than the 25–29-year age group. Another study found that the increased risk of miscarriage in pregnancies from older men is mainly seen in the first trimester. Yet another study found an increased risk in women, by the age of 45, on the order of 800% (compared to the 20–24 age group in that study), 75% of pregnancies ended in miscarriage.
or Campylobacter
, but can often be controlled by vaccination. Other diseases are also known to target animals for miscarriage. Spontaneous abortion occurs in pregnant Prairie Vole
s when their mate is removed and they are exposed to a new male, an example of the Bruce effect
, although this effect is seen less in wild populations than in the laboratory. Female mice that had spontaneous abortions showed a sharp rise in the time spent with unfamiliar males preceding the abortion.
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
at a stage where the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
or fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
. Miscarriage is the most common complication of early pregnancy.
Terminology
Very early miscarriages—those that occur before the sixth week LMPGestational age
Gestational age relates to the age of an embryo or fetus . There is some ambiguity in how it is defined:*In embryology, gestational age is the time elapsed since conception. This interval is also termed fertilisation age....
(since the woman's Last Menstrual Period)—are medically termed early pregnancy loss or chemical pregnancy. Miscarriages that occur after the sixth week LMP are medically termed clinical spontaneous abortion.
In medical (and veterinary) contexts, the technical term "abortion
Abortion
Abortion is defined as the termination of pregnancy by the removal or expulsion from the uterus of a fetus or embryo prior to viability. An abortion can occur spontaneously, in which case it is usually called a miscarriage, or it can be purposely induced...
" refers to any process by which a pregnancy ends with the death and removal or expulsion of the fetus, regardless of whether it is spontaneous or intentionally induced. Many women who have had miscarriages, however, object to the term "abortion" in connection with their experience, because in everyday English the word is strongly associated with induced abortions. In recent years there has been discussion in the medical community about avoiding the use of this term in favor of the less ambiguous term "miscarriage". In 2005 the European Society for Human Reproduction and Embryology (ESHRE) published a paper aiming to facilitate an update and revision of nomenclature used to describe early pregnancy events.
Labour resulting in live birth before the 37th week of pregnancy is termed "premature birth
Premature birth
In humans preterm birth refers to the birth of a baby of less than 37 weeks gestational age. The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging...
", even if the infant dies shortly afterward. The limit of viability
Limit of viability
-Scientific thresholds:There is no sharp limit of development, age, or weight at which a fetus automatically becomes viable. According to data years 2003-2005, 20 to 35 percent of babies born at 23 weeks of gestation survive, while 50 to 70 percent of babies born at 24 to 25 weeks, and more than 90...
at which 50% of fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
/infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
s survive longterm is around 24 weeks, with moderate or major neurological disability dropping to 50% only by 26 weeks. Although long-term survival has never been reported for infants born from pregnancy shorter than 21 weeks and 5 days, fetuses born as early as the 16th week of pregnancy may sometimes live for some minutes after birth.
A fetus that dies while in the uterus after about the 20–24th week of pregnancy is termed a "stillbirth
Stillbirth
A stillbirth occurs when a fetus has died in the uterus. The Australian definition specifies that fetal death is termed a stillbirth after 20 weeks gestation or the fetus weighs more than . Once the fetus has died the mother still has contractions and remains undelivered. The term is often used in...
"; the precise gestational age definition varies by country. Premature births or stillbirths are not generally considered miscarriages, though usage of the terms and causes of these events may overlap.
Classification
The clinical presentation of a threatened abortion describes any bleeding seen during pregnancy prior to viability, that has yet to be assessed further. At investigation it may be found that the fetus remains viable and the pregnancy continues without further problems.Alternatively the following terms are used to describe pregnancies that do not continue:
- An empty sacAnembryonic gestationAn anembryonic gestation is a pregnancy in which the very early pregnancy appears normal on an ultrasound scan, but as the pregnancy progresses a visible embryo never develops...
is a condition where the gestational sac develops normally, while the embryonic part of the pregnancy is either absent or stops growing very early. Other terms for this condition are blighted ovum and anembryonic pregnancy. - An inevitable abortion describes a condition in which the cervix has already dilated open, but the fetus has yet to be expelled. This usually will progress to a complete abortion. The fetal heart beat may have been shown to have stopped, but this is not part of the criteria.
- A complete abortion is when all products of conception have been expelled. Products of conception may include the trophoblastTrophoblastTrophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
, chorionic villiChorionic villiChorionic villi are villi that sprout from the chorion in order to give a maximum area of contact with the maternal blood.Embryonic blood is carried to the villi by the branches of the umbilical arteries, and after circulating through the capillaries of the villi, is returned to the embryo by the...
, gestational sacGestational sacThe gestational sac is the only available intrauterine structure that can be used to determine if an intrauterine pregnancy exists, until the embryo is identified....
, yolk sacYolk sacThe yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
, and fetal poleFetal poleThe fetal pole is a thickening on the margin of the yolk sac of a fetus during pregnancy.It is usually identified at 6.5 weeks with abdominal ultrasound imaging, and 6 weeks with vaginal ultrasound imaging. However it is quite normal for the fetal pole to not be visible until about 9 weeks...
(embryoEmbryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
); or later in pregnancy the fetusFetusA fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
, umbilical cordUmbilical cordIn placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
, placentaPlacentaThe placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
, amniotic fluid, and amniotic membraneAmniotic sacThe amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
. - An incomplete abortion occurs when tissueBiological tissueTissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
has been passed, but some remains in uteroIn uteroIn utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...
. - A missed abortion is when the embryo or fetus has died, but a miscarriage has not yet occurred. It is also referred to as delayed or missed miscarriage.
The following two terms consider wider complications or implications of a miscarriage:
- A septic abortionSeptic abortionA septic abortion or septic miscarriage is a form of miscarriage that is associated with a serious uterine infection. The infection carries risk of spreading infection to other parts of the body and cause septicaemia, a grave risk to the life of the woman.-Causes:A septic abortion can occur when...
occurs when the tissue from a missed or incomplete abortion becomes infected. The infection of the womb carries risk of spreading infection (septicaemia) and is a grave risk to the life of the woman. - Recurrent pregnancy lossHabitual abortionHabitual abortion, recurrent miscarriage or recurrent pregnancy loss is the occurrence of three or more pregnancies that end in miscarriage of the fetus, usually before 20 weeks of gestation...
(RPL) or recurrent miscarriage (medically termed habitual abortion) is the occurrence of three consecutive miscarriages. If the proportion of pregnancies ending in miscarriage is 15%, then the probability of two consecutive miscarriages is 2.25% and the probability of three consecutive miscarriages is 0.34%. The occurrence of recurrent pregnancy loss is 1%. A large majority (85%) of women who have had two miscarriages will conceive and carry normally afterwards.
The physical symptoms of a miscarriage vary according to the length of pregnancy:
- At up to six weeks only small blood clots may be present, possibly accompanied by mild cramping or period pain.
- At 6 to 13 weeks a clot will form around the embryo or fetus, and the placenta, with many clots up to 5 cm in size being expelled prior to a completed miscarriage. The process may take a few hours or be on and off for a few days. Symptoms vary widely and can include vomiting and loose bowels, possibly due to physical discomfort.
- At over 13 weeks the fetus may be easily passed from the womb, however the placenta is more likely to be fully or partially retained in the uterus, resulting in an incomplete abortion. The physical signs of bleeding, cramping and pain can be similar to an early miscarriage, but sometimes more severe and labour-like.
Signs and symptoms
The most common symptom of a miscarriage is bleeding; bleeding during pregnancy may be referred to as a threatened abortion. Of women who seek clinical treatment for bleeding during pregnancy, about half will go on to have a miscarriage. Symptoms other than bleeding are not statistically related to miscarriage.Miscarriage may also be detected during an ultrasound exam, or through serial human chorionic gonadotropin
Human chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
(HCG) testing. Women pregnant from ART
Assisted reproductive technology
Assisted reproductive technology is a general term referring to methods used to achieve pregnancy by artificial or partially artificial means. It is reproductive technology used primarily in infertility treatments. Some forms of ART are also used in fertile couples for genetic reasons...
methods, and women with a history of miscarriage, may be monitored closely and so detect a miscarriage sooner than women without such monitoring.
Several medical options exist for managing documented nonviable pregnancies that have not been expelled naturally.
Psychological
Although a woman physically recovers from a miscarriage quickly, psychological recovery for parents in general can take a long time. People differ greatly in this regard: some are able to move on after a few months, but others take more than a year. Still others may feel relief or other less negative emotions. A questionnaire (GHQ-12 General Health Questionnaire) study following women having miscarried showed that half (55%) of the miscarrying women presented with significant psychological distress immediately, 25% at 3 months; 18% at 6 months, and 11% at 1 year after miscarriage.For those who do go through a process of grief
Grief
Grief is a multi-faceted response to loss, particularly to the loss of someone or something to which a bond was formed. Although conventionally focused on the emotional response to loss, it also has physical, cognitive, behavioral, social, and philosophical dimensions...
, it is often as if a baby had been born but died. How short a time the fetus lived in the womb may not matter for the feeling of loss. From the moment pregnancy is discovered, the parents can start to bond with the embryo or fetus. When the pregnancy turns out not to be viable, dreams, fantasies and plans for the future are roughly disturbed.
Besides the feeling of loss, a lack of understanding by others is often important. People who have not experienced a miscarriage themselves may find it hard to empathize
Empathy
Empathy is the capacity to recognize and, to some extent, share feelings that are being experienced by another sapient or semi-sapient being. Someone may need to have a certain amount of empathy before they are able to feel compassion. The English word was coined in 1909 by E.B...
with what has occurred and how upsetting it may be. This may lead to unrealistic expectations of the parents' recovery. The pregnancy and miscarriage are hardly mentioned any more in conversation, often because the subject is too painful. This can make the woman feel particularly isolated. Inappropriate or insensitive responses from the medical profession can add to the distress and trauma experienced, so in some cases attempts have been made to draw up a standard code of practice.
Interaction with pregnant women and newborn children is often also painful for parents who have experienced miscarriage. Sometimes this makes interaction with friends, acquaintances and family very difficult.
Causes
Miscarriages can occur for many reasons, not all of which can be identified. Some of these causes include genetic, uterine or hormonal abnormalities, reproductive tract infections, and tissue rejection.First trimester
Most clinically apparent miscarriages (two thirds to three-quarters in various studies) occur during the first trimester.Chromosomal abnormalities are found in more than half of embryos miscarried in the first 13 weeks. A pregnancy with a genetic problem has a 95% probability of ending in miscarriage. Most chromosomal problems happen by chance, have nothing to do with the parents, and are unlikely to recur. Chromosomal problems due to a parent's genes are, however, a possibility. This is more likely to have been the cause in the case of repeated miscarriages, or if one of the parents has a child or other relatives with birth defects. Genetic problems are more likely to occur with older parents; this may account for the higher miscarriage rates observed in older women.
Another cause of early miscarriage may be progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
deficiency. Women diagnosed with low progesterone levels in the second half of their menstrual cycle (luteal phase
Luteal phase
The luteal phase is the latter phase of the menstrual cycle or the estrous cycle . It begins with the formation of the corpus luteum and ends in either pregnancy or luteolysis...
) may be prescribed progesterone supplements, to be taken for the first trimester of pregnancy. No study has shown that general first-trimester progesterone supplements reduce the risk of threatened miscarriage (when a mother might already be losing her baby), and even the identification of problems with the luteal phase as contributing to miscarriage has been questioned.
Second trimester
Up to 15% of pregnancy losses in the second trimester may be due to uterine malformationUterine malformation
A uterine malformation is a type of female genital malformation resulting from an abnormal development of the Müllerian duct during embryogenesis...
, growths in the uterus (fibroids), or cervical problems
Cervical incompetence
Cervical incompetence is a medical condition in which a pregnant woman's cervix begins to dilate and efface before her pregnancy has reached term. Internal os opening more than 1 cm is abnormal and cervical length less than 2 cm is considered diagnostic...
. These conditions may also contribute to premature birth
Premature birth
In humans preterm birth refers to the birth of a baby of less than 37 weeks gestational age. The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging...
.
One study found that 19% of second trimester losses were caused by problems with the umbilical cord
Umbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
. Problems with the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
may also account for a significant number of later-term miscarriages.
General risk factors
Pregnancies involving more than one fetus are at increased risk of miscarriage.Uncontrolled diabetes greatly increases the risk of miscarriage. Women with controlled diabetes are not at higher risk of miscarriage. Because diabetes may develop during pregnancy (gestational diabetes
Gestational diabetes
Gestational diabetes is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy . It is widely accepted as a disease only in the United States, there is some question whether the condition is natural during pregnancy...
), an important part of prenatal care
Prenatal care
Prenatal care refers to the medical and nursing care recommended for women before and during pregnancy. The aim of good prenatal care is to detect any potential problems early, to prevent them if possible , and to direct the woman to appropriate specialists, hospitals, etc...
is to monitor for signs of the disease.
Polycystic ovary syndrome is a risk factor for miscarriage, with 30-50% of pregnancies in women with PCOS being miscarried in the first trimester. Two studies have shown treatment with the drug metformin
Metformin
Metformin is an oral antidiabetic drug in the biguanide class. It is the first-line drug of choice for the treatment of type 2 diabetes, in particular, in overweight and obese people and those with normal kidney function. Its use in gestational diabetes has been limited by safety concerns...
to significantly lower the rate of miscarriage in women with PCOS (the metformin-treated groups experienced approximately one-third the miscarriage rates of the control groups). However, a 2006 review of metformin treatment in pregnancy found insufficient evidence of safety and did not recommend routine treatment with the drug.
High blood pressure
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
during pregnancy, known as preeclampsia, is sometimes caused by an inappropriate immune reaction (paternal tolerance) to the developing fetus, and is associated with the risk of miscarriage. Similarly, women with a history of recurrent miscarriages are at risk of developing preeclampsia.
Severe cases of hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
increase the risk of miscarriage. The effect of milder cases of hypothyroidism on miscarriage rates has not been established. The presence of certain immune conditions such as autoimmune disease
Autoimmunity
Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which allows an immune response against its own cells and tissues. Any disease that results from such an aberrant immune response is termed an autoimmune disease...
s is associated with a greatly increased risk of miscarriage. The presence of anti-thyroid autoantibodies
Anti-thyroid autoantibodies
Anti-thyroid autoantibodies are autoantibodies targeted against one or more components of the thyroid. The main types of anti-thyroid autoantibodies are anti-thyroid peroxidase antibodies and stimulating autoantibodies that are associated with Grave's disease.-Anti-TPO antibodies:Aanti-thyroid...
is associated with an increased risk of miscarriage with an odds ratio
Odds ratio
The odds ratio is a measure of effect size, describing the strength of association or non-independence between two binary data values. It is used as a descriptive statistic, and plays an important role in logistic regression...
of 3.73 and 95% confidence interval
Confidence interval
In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...
1.8–7.6.
Certain illnesses (such as rubella
Rubella
Rubella, commonly known as German measles, is a disease caused by the rubella virus. The name "rubella" is derived from the Latin, meaning little red. Rubella is also known as German measles because the disease was first described by German physicians in the mid-eighteenth century. This disease is...
, chlamydia and others) increase the risk of miscarriage.
Tobacco (cigarette) smokers have an increased risk of miscarriage. An increase in miscarriage is also associated with the father being a cigarette smoker. The husband study observed a 4% increased risk for husbands who smoke fewer than 20 cigarettes/day, and an 81% increased risk for husbands who smoke 20 or more cigarettes/day.
Cocaine use increases miscarriage rates. Physical trauma, exposure to environmental toxins, and use of an IUD during the time of conception have also been linked to increased risk of miscarriage.
Antidepressants specially paroxetine
Paroxetine
Paroxetine is an SSRI antidepressant. Marketing of the drug began in 1992 by the pharmaceutical company SmithKline Beecham, now GlaxoSmithKline...
and venlafaxine
Venlafaxine
Venlafaxine is an antidepressant of the serotonin-norepinephrine reuptake inhibitor class. First introduced by Wyeth in 1993, now marketed by Pfizer, it is licensed for the treatment of major depressive disorder , as a treatment for generalized anxiety disorder, and comorbid indications in...
can lead to spontaneous abortion.
The age of the mother is a significant risk factor. Miscarriage rates increase steadily with age, with more substantial increases after age 35.
Suspected risk factors
Several factors have been correlated with higher miscarriage rates, but whether they cause miscarriages is debated. No causal mechanism may be known, the studies showing a correlation may have been retrospective (beginning the study after the miscarriages occurred, which can introduce bias) rather than prospective (beginning the study before the women became pregnant), or both.Autoimmune disease
Some research suggests autoimmunity as a possible cause of recurrent or late-term miscarriages. Autoimmune diseaseAutoimmune disease
Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...
occurs when the body's own immune system acts against itself. Therefore, in the case of an autoimmune-induced miscarriage the woman's body attacks the growing fetus or prevents normal pregnancy progression. Further research has also suggested that autoimmune disease can cause genetic abnormalities in embryos which in turn can lead to miscarriage.
Morning sickness
Nausea and vomiting of pregnancy (NVP, or morning sicknessMorning sickness
Morning sickness, also called nausea gravidarum, nausea, vomiting of pregnancy , or pregnancy sickness is a condition that affects more than half of all pregnant women. Related to increased oestrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or...
) are associated with a decreased risk of miscarriage. Several mechanisms have been proposed for this relationship, but none are widely agreed on. Because NVP may alter a woman's food intake and other activities during pregnancy, it may be a confounding factor when investigating possible causes of miscarriage.
Exercise
One such factor is exercise. A study of over 92,000 pregnant women found that most types of exercise (with the exception of swimming) correlated with a higher risk of miscarriage prior to 18 weeks. Increasing time spent on exercise was associated with a greater risk of miscarriage: an approximately 10% increased risk was seen with up to 1.5 hours per week of exercise, and a 200% increased risk was seen with over 7 hours per week of exercise. High-impact exercise was especially associated with the increased risk. No relationship was found between exercise and miscarriage rates after the 18th week of pregnancy. The majority of miscarriages had already occurred at the time women were recruited for the study, and no information on nausea during pregnancy or exercise habits prior to pregnancy was collected.Caffeine
CaffeineCaffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
consumption has also been correlated to miscarriage rates, at least at higher levels of intake. A 2007 study of over 1,000 pregnant women found that women who reported consuming 200 mg or more of caffeine per day experienced a 25% miscarriage rate, compared to 13% among women who reported no caffeine consumption. 200 mg of caffeine is present in 10 oz (300 mL) of coffee or 25 oz (740 mL) of tea. This study controlled for pregnancy-associated nausea and vomiting (NVP or morning sickness): the increased miscarriage rate for heavy caffeine users was seen regardless of how NVP affected the women. About half of the miscarriages had already occurred at the time women were recruited for the study. A second 2007 study of approximately 2,400 pregnant women found that caffeine intake up to 200 mg per day was not associated with increased miscarriage rates (the study did not include women who drank more than 200 mg per day past early pregnancy). A prospective cohort study in 2009 showed no increased risk.
Diagnosis
A miscarriage can be confirmed via ultrasoundUltrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
and by the examination of the passed tissue. When looking for microscopic pathologic
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
symptoms of miscarriage, one looks for the products of conception. Microscopically, these include villi
Chorionic villi
Chorionic villi are villi that sprout from the chorion in order to give a maximum area of contact with the maternal blood.Embryonic blood is carried to the villi by the branches of the umbilical arteries, and after circulating through the capillaries of the villi, is returned to the embryo by the...
, trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
, fetal parts, and background gestational changes in the endometrium
Endometrium
-Function:The endometrium is the innermost glandular layer and functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a...
. Genetic tests may also be performed to look for abnormal chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
arrangements.
Management
Blood loss during early pregnancy is the most common symptom of both miscarriage and of ectopic pregnancyEctopic pregnancy
An ectopic pregnancy, or eccysis , is a complication of pregnancy in which the embryo implants outside the uterine cavity. With rare exceptions, ectopic pregnancies are not viable. Furthermore, they are dangerous for the parent, since internal haemorrhage is a life threatening complication...
. Pain does not strongly correlate with miscarriage, but is a common symptom of ectopic pregnancy. In the case of concerning blood loss, pain, or both, transvaginal ultrasound
Obstetric ultrasonography
Obstetric sonography is the application of medical ultrasonography to obstetrics, in which sonography is used to visualize the embryo or foetus in its mother's uterus...
is performed. If a viable intrauterine pregnancy is not found with ultrasound, serial βHCG
Human chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
tests should be performed to rule out ectopic pregnancy, which is a life-threatening situation.
If the bleeding is light, making an appointment to see one's doctor is recommended. If bleeding is heavy, there is considerable pain, or there is a fever, then emergency medical attention is recommended to be sought.
Whilst bed rest
Bed rest
Bed rest is a medical treatment involving a period of consistent recumbence in bed. It is used as a treatment for an illness or medical condition, especially when prescribed or chosen rather than resulting from severe prostration or imminent death...
has been advocated in the past to help ensure that the pregnancy might continue, and in one study possibly helped when small subchorionic hematoma had been found on ultrasound scans, the prevailing opinion is that this is of no proven benefit.
No treatment is necessary for a diagnosis of complete abortion (as long as ectopic pregnancy is ruled out). In cases of an incomplete abortion, empty sac, or missed abortion there are three treatment options:
- With no treatment (watchful waitingWatchful waitingWatchful waiting is an approach to a medical problem in which time is allowed to pass before medical intervention or therapy is used. During this time, repeated testing may be performed....
), most of these cases (65–80%) will pass naturally within two to six weeks. This path avoids the side effects and complications possible from medications and surgery. - Medical management usually consists of using misoprostolMisoprostolMisoprostol is a drug that is used for the prevention of non steroidal anti inflammatory drug induced gastric ulcers, for early abortion, to treat missed miscarriage, and to induce labor. The latter use is controversial in the United States. Misoprostol was invented and marketed by G.D...
(a prostaglandinProstaglandinA prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....
, brand name Cytotec) to encourage completion of the miscarriage. About 95% of cases treated with misoprostol will complete within a few days. - Surgical treatment (most commonly vacuum aspiration, sometimes referred to as a D&CDilation and curettageDilation and curettage refers to the dilation of the cervix and surgical removal of part of the lining of the uterus and/or contents of the uterus by scraping and scooping . It is a diagnostic gynecological procedure.D&C normally is referred to a procedure involving a curette, also called sharp...
or D&EDilation and evacuationDilation and evacuation literally refers to the dilation of the cervix and surgical evacuation of the contents of the uterus...
) is the fastest way to complete the miscarriage. It also shortens the duration and heaviness of bleeding, and avoids the physical pain associated with the miscarriage. In cases of repeated miscarriage, D&C is also the most convenient way to obtain tissue samples for karyotype analysis (cytogenetic or molecular), although it is also possible to do with expectant and medical management. D&C, however, has a higher risk of complications, including risk of injury to the cervix (e.g. cervical incompetenceCervical incompetenceCervical incompetence is a medical condition in which a pregnant woman's cervix begins to dilate and efface before her pregnancy has reached term. Internal os opening more than 1 cm is abnormal and cervical length less than 2 cm is considered diagnostic...
) and uterus, perforation of the uterus, and potential scarring of the intrauterine lining (Asherman's syndromeAsherman's syndromeAsherman's syndrome , also called "uterine synechiae" or intrauterine adhesions , presents a condition characterized by the presence of adhesions and/or fibrosis within the uterine cavity due to scars...
). This is an important consideration for women who would like to have children in the future and want to preserve their fertility and reduce the chance of future obstetric complications.
Prevention
Currently there is no known way to prevent an impending miscarriage. However, fertility experts believe that identifying the cause of the miscarriage may help prevent it from happening again in a future pregnancy. In one study, researchers found that use of the supplement dehydroepiandrosteroneDehydroepiandrosterone
5-Dehydroepiandrosterone is a 19-carbon endogenous steroid hormone. It is the major secretory steroidal product of the adrenal glands and is also produced by the gonads and the brain. DHEA is the most abundant circulating steroid in humans....
before and during pregnancy reduced the risk of pregnancy losses.
Epidemiology
Determining the prevalencePrevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of miscarriage is difficult. Many miscarriages happen very early in the pregnancy, before a woman may know she is pregnant. Treatment of women with miscarriage at home means medical statistics on miscarriage miss many cases. Prospective studies using very sensitive early pregnancy tests have found that 25% of pregnancies are miscarried by the sixth week LMP
Gestational age
Gestational age relates to the age of an embryo or fetus . There is some ambiguity in how it is defined:*In embryology, gestational age is the time elapsed since conception. This interval is also termed fertilisation age....
(since the woman's Last Menstrual Period). However, other sources reports suggest higher rates. One fact sheet from the University of Ottawa states, "The incidence of spontaneous abortion is estimated to be 50% of all pregnancies, based on the assumption that many pregnancies abort spontaneously with no clinical recognition." The NIH reports, "It is estimated that up to half of all fertilized eggs die and are lost (aborted) spontaneously, usually before the woman knows she is pregnant. Among those women who know they are pregnant, the miscarriage rate is about 15-20%." Clinical miscarriages (those occurring after the sixth week LM) occur in 8% of pregnancies.
The risk of miscarriage decreases sharply after the 10th week LMP, i.e. when the fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
stage begins. The loss rate between 8.5 weeks LMP and birth is about two percent; loss is “virtually complete by the end of the embryonic period."
The prevalence of miscarriage increases considerably with age of the parents. One study found that pregnancies from men younger than 25 years are 40% less likely to end in miscarriage than pregnancies from men 25–29 years. The same study found that pregnancies from men older than 40 years are 60% more likely to end in miscarriage than the 25–29-year age group. Another study found that the increased risk of miscarriage in pregnancies from older men is mainly seen in the first trimester. Yet another study found an increased risk in women, by the age of 45, on the order of 800% (compared to the 20–24 age group in that study), 75% of pregnancies ended in miscarriage.
In other animals
Miscarriage occurs in all animals that experience pregnancy. There are a variety of known risk factors for miscarriage in non-human animals. For example, in sheep, it may be caused by crowding through doors, or being chased by dogs. In cows, miscarriage (i.e. spontaneous abortion) may be caused by contagious disease, such as BrucellosisBrucellosis
Brucellosis, also called Bang's disease, Crimean fever, Gibraltar fever, Malta fever, Maltese fever, Mediterranean fever, rock fever, or undulant fever, is a highly contagious zoonosis caused by ingestion of unsterilized milk or meat from infected animals or close contact with their secretions...
or Campylobacter
Campylobacter
Campylobacter is a genus of bacteria that are Gram-negative, spiral, and microaerophilic. Motile, with either unipolar or bipolar flagella, the organisms have a characteristic spiral/corkscrew appearance and are oxidase-positive. Campylobacter jejuni is now recognized as one of the main causes...
, but can often be controlled by vaccination. Other diseases are also known to target animals for miscarriage. Spontaneous abortion occurs in pregnant Prairie Vole
Prairie Vole
The Prairie Vole is a small vole found in central North America. The vole has long, coarse grayish-brown fur on the upper portion of the body and yellowish fur on the lower portion of the body...
s when their mate is removed and they are exposed to a new male, an example of the Bruce effect
Bruce effect
The Bruce effect, or pregnancy block, refers to the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect has primarily been studied in laboratory mice , but is also observed in deer-mice, meadow voles, and collared lemmings...
, although this effect is seen less in wild populations than in the laboratory. Female mice that had spontaneous abortions showed a sharp rise in the time spent with unfamiliar males preceding the abortion.
ICD10 codes
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N96 O03.0-O06.4 O02.1 O20.0 |