Prenatal nutrition and birth weight
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....

 and weight management
Weight Management
Weight management is a long-term approach to a healthy lifestyle. It includes a balance of healthy eating and physical exercise to equate energy expenditure and energy intake. Developing healthy eating habits while using tips that will keep us fuller longer can be useful tools in weight management...

 before and during 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...

 has a profound effect on the development of infants. This is a rather critical time for healthy fetal development as infants rely heavily on maternal stores and nutrient for optimal growth and health outcome later in life. Prenatal nutrition addresses nutrient recommendations before and during pregnancy. Birth weight
Birth weight
Birth weight is the body weight of a baby at its birth.There have been numerous studies that have attempted, with varying degrees of success, to show links between birth weight and later-life conditions, including diabetes, obesity, tobacco smoking and intelligence.-Determinants:There are...

of the newborn at delivery reflects the sufficiency and the quality of maternal nutrient for the fetus during pregnancy. Prenatal nutrition has a strong influence on birth weight and further development of the infant.

A common saying that 'a woman is eating for two while pregnant' implies that a mother should consume twice as much during pregnancy. However, in reality this is not true. Although maternal consumption will directly affect both herself and the growing 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...

, over eating excessively will compromise the baby's health as the infant will have to work extra hard to become healthy in the future. Compared with the infant, the mother possesses the least biological risk. Therefore, excessive calories, rather than going to the infant, often get stored as fat in the mother. On the other hand, insufficient consumption will result in lower birth weight.

Maintaining a healthy weight during 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 ....

 lowers adverse risks on infants such as birth defects, as well as chronic conditions in adulthood such as obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

, diabetes, and cardiovascular disease
Cardiovascular disease
Heart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...

 (CVD). Ideally, the rate of weight gain should be monitored during pregnancy to support the most ideal infant development.

Barker's Hypothesis

The "Barker Hypothesis", or Thrifty phenotype
Thrifty phenotype
The thrifty phenotype hypothesis says that reduced fetal growth is strongly associated with a number of chronic conditions later in life. This increased susceptibility results from adaptations made by the fetus in an environment limited in its supply of nutrients...

, states that conditions during pregnancy will have long term effects on adult health. Associated risk of lifelong diseases includes cardiovascular disease
Cardiovascular disease
Heart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...

, type-2 diabetes, obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

, and 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...

. Babies born lighter in weight appear to have an increased rate of mortality than babies born at a heavier weight. This does not mean that heavy babies are less of a concern. Death rate would rise as birth weight increases beyond normal birth weight range. Therefore, it is important to maintain a healthy gestational weight gain throughout pregnancy for achieving the optimal infant birth weight.

When this theory was first proposed, it was not well accepted and was met with much skepticism. The main criticism was that confounding
In statistics, a confounding variable is an extraneous variable in a statistical model that correlates with both the dependent variable and the independent variable...

 variables such as environmental factors could attribute to many of the chronic diseases such that low birth weight alone should not be dictated as an independent risk factor. Subsequent research studies supporting the theory attempted to adjust these environmental factors and in turn, provided more convincing results with minimal confounding variables.

"Barker's Hypothesis" is also known as “Fetal Programming Hypothesis”. The word “programming” illustrates the idea that during critical periods in early fetal development, there are persisting changes in the body structure and function that are caused by environmental stimuli. This relates to the concept of developmental plasticity where our genes can express different ranges of physiological or morphological states in response to the environmental conditions during fetal development.

If the mother has an inadequate diet then it signals the baby that the living condition in the long term will be impoverished. Consequently the baby adapts by changing its body size and metabolism to prepare for harsh conditions of food shortages after birth. Physiological and metabolic processes in the body undergo long term changes as a result of restricted growth. When the living environment switches from the condition of malnutrition to a society of abundant supply of nutrients, this exposes the baby to a bountiful environment that goes against what its body is designed for and this places the baby at a higher risk of adult diseases later in adulthood. By the same token, if the fetus growing in the womb of a healthy mother is exposed to prolonged famine after birth, the infant would be less adaptive to the harsh environment than low birth weight babies.

The Dutch Famine

Since small birth weight is associated with an increased risk of chronic diseases in later life, and poor maternal nutrition during gestation contributes to restricted fetal development, maternal malnutrition may be a cause of increased disease susceptibility in adulthood.

The Dutch famine of 1944
Dutch famine of 1944
The Dutch famine of 1944, known as the Hongerwinter in Dutch, was a famine that took place in the German-occupied part of the Netherlands, especially in the densely populated western provinces above the great rivers, during the winter of 1944-1945, near the end of World War II. A German blockade...

or the 'Hunger Winter' during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 serves as an epidemiological study that is used to examine the effects of maternal under-nutrition during different gestational stages. The famine was a period (roughly five to six months) of extreme food shortage in the west of Netherlands. The famine was imposed on a previously well-nourished population and the official daily ration for the general adult population gradually decreased from 1800 calories in December 1943 to 1400 calories in October 1944 to below 1000 calories in the late November 1944. December 1944 to April 1945 was the peak of the famine where the official daily ration fell abruptly to about 400~800 calories. Even though pregnant and lactating women had extra food during the famine, these extra supplies could no longer be provided at the height of the famine. In the early May 1945, the liberation of the Netherlands restored the food supply. The daily ration had increased to more than 2000 calories in June 1945. What is unique about Dutch Famine as an experimental study on the effects of maternal malnutrition is that the population was strictly circumscribed in time and place and the sudden onset and relief of the famine was imposed on a previously well-nourished population.

The Dutch Famine during World War II had a profound effect on the health condition of the general public, especially women who conceived during the period of time. The period of maternal starvation is shown to have limited intrauterine growth and has been identified as one of the most important contributor to coronary heart disease
Coronary heart disease
Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...

 as well as other chronic diseases later in life. These findings agree well with Barker’s hypothesis; it supports the theory that maternal under-nutrition leads to a lower birth weight due to restricted intrauterine development and ultimately leads to higher risks of chronic conditions in adult life.

Gestation Stages

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 ....

 is the period of embryo development from conception
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...

 to birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...

. Gestation is about 40 weeks in humans and is divided into three trimesters, each spanning 3 months. Gestational stages, on the other hand, are based on physiological fetal development, which include blastogenesis, embryonic stage and fetal stage.

Blastogenesis is the stage from fertilization to about 2 weeks. The fertilized egg or the zygote becomes a blastocyst where the outer layer and the inner cell mass differentiate to form placenta and the fetus respectively. Implantation occurs at this stage where the blastocyst becomes buried in the 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...


Embryonic stage is approximately from 2 weeks to 8 weeks. It is also in this stage where the blastocyst develops into an 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...

, where all major features of human are present and operational by the end of this stage.

Fetal stage is from 9 weeks to term. During this period of time, the embryo develops rapidly and becomes a 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...

. Pregnancy becomes visible at this stage.

Pre-pregnancy Weight and Moochy Gestational Weight Gain

The pattern and amount of weight gain is closely associated with gestational stages. Additional energy is required during pregnancy due to the expansion of maternal tissues and stores in order to support fetal development.

In the first trimester (blastogenesis and early embryonic stages), the mother experiences a minimal weight gain (approximately 0.5-2 kilograms), while the 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...

 weighs only 6 grams, which is approximately the weight 6 raisins.

In the second trimester and third trimester (late embryonic and fetal stages), the fetus undergoes rapid weight growth and the weight increases to about 3000~4000 grams. It is also in this period that the mother experiences the bulk of her gestational weight gain but the amount of weight gain varies greatly. The amount of weight gain depends strongly on their pre-pregnant weight.

Generally, a normal weight is strongly recommended for mothers when entering gestation, as it promotes overall health of infants. Maternal body weight is determined by the Body Mass Index
Body mass index
The body mass index , or Quetelet index, is a heuristic proxy for human body fat based on an individual's weight and height. BMI does not actually measure the percentage of body fat. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing...

 (BMI) which is defined as the weight in kilograms divided by the square of the height in meters.
While pregnant, body weight should be managed within the recommended gestational weight gain range as it is shown to have a positive effect on pregnancy outcomes. Gestational weight gain should also be progressive and the recommended weight depends on pre-pregnant body weight.

Since the total weight gain depends on pre-pregnant body weight, it is recommended that underweight women should undergo a larger weight gain for healthy pregnancy outcomes, and overweight or obese women should undergo a smaller weight gain.

Normal Weight Women

Women having a BMI of 18.5~24.9 are classified as having a normal or healthy body weight. This group have the lowest risk of adverse birth outcomes. Their babies are least likely to either be low-birth weight or high-birth weight. It is advised that women with a normal weight before pregnancy should gain a total of 11.5 kilograms to 16.0 kilograms throughout gestation, which is approximately 0.4 kilogram per week in the second and third trimesters.

In order to maintain a steady weight gain, the mother should engage in mild physical activities. Participating in aerobic
Aerobic exercise
Aerobic exercise is physical exercise of relatively low intensity that depends primarily on the aerobic energy-generating process. Aerobic literally means "living in air", and refers to the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism...

 activities such as walking and swimming 3 to 4 times a week is usually adequate. Vigorous physical activity is not recommended since an excessive loss of calories is induced which is not sufficient to support fetal development.

A proper diet is also essential to healthy weight gain. The common saying “a women is eating for two” often leads to mothers thinking that they should eat twice as much. In reality, only a small increase in caloric intake is needed to provide for the fetus; approximately 350 calories more in the second trimester and 450 calories more in the third trimester. Also, healthy choices should be emphasized for these extra calories such as whole grain
Whole grain
Whole grains are cereal grains that contain cereal germ, endosperm, and bran, in contrast to refined grains, which retain only the endosperm. Whole grains can generally be sprouted while refined grains generally will not sprout. Whole-meal products are made by grinding whole grains in order to make...

 products, fruits and vegetables as well as low-fat dairy alternatives.

Underweight Women

Women's are classified as underweight if they have a pre-pregnant BMI of 18.5 or below. Low pre-pregnancy BMI increases the risk of low birth weight infants, but the risk can be balanced by an appropriate gestational weight gain from 12.5 to 18.0 kilograms in total, or about 0.5 kilogram each week in the second and third trimesters.

Underweight women usually have inadequate nutrient stores that are not enough to provide for both herself and the fetus. While exercise and a proper diet are both needed to maintain the recommended weight gain, a balance between the two is very important. As such, underweight mothers should seek individualized advice tailored especially for themselves.

Overweight and Obese Women

Women with a high pre-pregnancy weight are classified as overweight or obese, defined as having a BMI of 25 or above. Women with BMI between 25 and 29.9 are in the overweight category and should gain between 7.0 and 11.5 kilograms in total, corresponding to approximately 0.28 kilogram each week during the second and third trimesters. Whereas women with BMI of 30 or above are in the obese category and should gain only between 5.0 and 9.0 kilograms overall, which equates to roughly 0.2 kilogram per week in the second and third trimesters.

In general, walking is encouraged for mothers classified in this category. Unfortunately, estimated energy requirements for them are not available. As such, they are encouraged to record activity and intake level. This can be done with the help of tools such as My Food Guide Servings Tracker from Health Canada
Health Canada
Health Canada is the department of the government of Canada with responsibility for national public health.The current Minister of Health is Leona Aglukkaq, a Conservative Member of Parliament appointed to the position by Prime Minister Stephen Harper.-Branches, regions and agencies:Health Canada...

 and EATracker that are available online. In extreme cases where the BMI exceeds 35, help from a registered dietitian
Dietitians supervise the preparation and service of food, develop modified diets, participate in research, and educate individuals and groups on good nutritional habits. The goals of dietitians are to provide medical nutritional intervention, and to obtain, safely prepare, serve and advise on...

 is recommended.

Summary Table

The following table summarizes the recommended rate of weight gain and total weight gain according to pre-pregnancy BMI for singleton pregnancies. The first column categorizes the type of body weight based on the Body Mass Index. The second column summarizes the total recommended weight gain for each type of body weight, and the third column presents the corresponding weekly weight gain during the period when the fetus undergoes rapid growth (during second and third trimesters). In extreme cases, the amount of total and weekly weight gain can vary by a factor of two depending on a woman's pre-pregnant weight. For example, a woman in the obese category is recommended to gain a total of 5~9 kilograms, whereas an underweight woman needs to gain up to 18 kilograms in weight.
Pre-pregnancy BMI Category Recommendated Total Weight Gain Weekly Weight Gain
(after 12 weeks)
The term underweight refers to a human who is considered to be under a healthy weight. "Underweight" means weighing less than what is expected to be a healthy person . The definition is usually made with reference to the body mass index . A BMI of under 18.5 is usually referred to as underweight...

BMI <18.5
12.5~18 kg (28~40 lb) 0.5 kg (1.0 lb)
Healthy weight
BMI 18.5~ 24.9
11.5~16 kg (25~35 lb) 0.4 kg (1.0 lb)
Overweight is generally defined as having more body fat than is optimally healthy. Being overweight is a common condition, especially where food supplies are plentiful and lifestyles are sedentary...

BMI 25.0~ 29.9
7.0~ 11.5 kg (15~25 lb) 0.3 kg (0.6 lb)
BMI > 30
5.0~9.0 kg (11~20 lb) 0.2 kg (0.5 lb)


In order to have a good estimate of birth weight, ultrasonography or ultrasound
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...

 during pregnancy and the date of last menstrual period are needed. Measured values from ultrasonography are compared with the growth chart to estimate fetal weight.

Crown rump length can be used as the best ultrasonographic measurement for correct diagnosis of gestational age during the first trimester. This correlation between crown rump length and gestational age would be most effectively shown when no growth defects are observed in first trimester. If growth defects were observed in the first trimester, then the measurement of the date of last menstrual period becomes quite important since the crown heel length has become less of a reliable indicator of gestational age.

After the 20th week of pregnancy, the mother would need to visit the doctor for the measurement of fundal height
Fundal height
Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development. It is measured from the top of the mother's uterus to the top of the mother's pubic bone in centimeters. It should match the fetus' gestational age in weeks within 1 to 3 cm,...

, which is the length from the top portion of the uterus to the pubic bone. The length measured in centimeters should correspond to the number of weeks that the mother has been pregnant. If the measured number is higher or lower than 2 centimetres, further tests using ultrasound would be needed to check the results. Another way to estimate fetal size is to look at the mother’s weight gain. How much weight the mother gains can be used to indicate fetal size.

Low Birth Weight

There are two ways to determine small for gestational age
Small for gestational age
Small for gestational age babies are those who are smaller in size than normal for the baby's sex and gestational age, most commonly defined as a weight below the 10th percentile for the gestational age.-Terminology:...

 infants. Many research studies agree that SGA
SGA can mean several things, including:* Grothendieck's Séminaire de géométrie algébrique* Old Irish language * Schwarz-Gelbe Allianz , an Austrian political party...

 babies are those with birth weight or crown heel length measured at two standard deviations or more below the mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....

 of the infant’s gestational age, based on data consisting of a reference population. Other studies classify SGA babies as those with birth weight values below the 10th percentile of the growth chart for babies of the same gestational age. This indicates that these babies are weighing less than 90% of babies of the same gestational age.

Many factors, including maternal, placental, and fetal factors, contribute to the cause of impaired fetal growth. There are a number of maternal factors, which include age, nutritional status, alcohol abuse, smoking, and medical conditions. Insufficient uteroplacental perfusion is an example of a placental factor. Chromosomal abnormalities and genetic diseases are examples of fetal factors.
Identification of the causes of SGA for individual cases aids health professionals in finding ways to handle each unique case. Nutritional counseling, education, and consistent monitoring can be helpful to assist women bearing SGA infants.

Complications for the infant include limitations in body growth since the number and size of cells in tissues is smaller. The infant likely did not receive enough oxygen during pregnancy so the oxygen level is low. It is also more difficult to maintain body temperature since there is less blood flow within the small body.

As such, it is necessary to monitor oxygen level to make sure that it doesn’t go too low. If the baby can’t suck well, then it may be necessary for tube-feed. Since the baby cannot maintain body temperature sufficiently, a temperature-controlled bed would help to keep their bodies from losing heat. There are ways to help prevent SGA babies. Monitoring fetal growth can help identify the problem during pregnancy well before birth. It would be beneficial to seek professional help and counseling.

High Birth Weight

Research show that when birth weights of infants are greater than the 90th percentile of the growth chart
Growth chart
A growth chart is used by pediatricians and other health care providers to follow a child's growth over time. Growth charts have been constructed by observing the growth of large numbers of normal children over time...

 for babies of the same gestational age, they are considered large for gestational age
Large for gestational age
Large for gestational age is an indication of high prenatal growth rate, often defined as a weight that lies above the 90th percentile for that gestational age...

 or LGA. This indicates that these babies are weighing more than 90% of babies of the same gestational age.

Many factors account for LGA babies, including genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 and excessive nutrient supply. It seems that a common factor for LGA babies is whether or not the mother has diabetes when she is pregnant. An indicator for excessive growth, regardless of gestational age, is the appearance of macrosomia. Many complications are observed for LGA babies and their mothers. A longer delivery time may be expected since it is a difficult birth. The infant would likely suffer hypoglycemia (low glucose level in the blood) after birth. The infant would also have difficulty breathing.

There might be a need for early delivery if the baby gets too big and perhaps Caesarean section
Caesarean section
A Caesarean section, is a surgical procedure in which one or more incisions are made through a mother's abdomen and uterus to deliver one or more babies, or, rarely, to remove a dead fetus...

 would be needed. Since the baby is bigger in size, there’s a higher chance of injury when coming out of the mother’s body. To increase the blood glucose level in blood, a glucose/water solution can be offered to the infant.

There are ways to help prevent LGA babies. It is necessary to monitor fetal growth and perform pregnancy examinations to determine health status and detect any possibility of unrecognized diabetes. For diabetic mothers, careful management of diabetes during pregnancy period would be helpful in terms of lowering some of the risks of LGA.

Points to Consider

The goal of pregnancy is to have a healthy baby. Maintaining healthy and steady weight gain during pregnancy promotes overall health and reduces the incidence of prenatal morbidity and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...

. This, in turn, has a positive effect on the baby’s health.

Since conditions during pregnancy will have long term effects on adult health, “moderation” should be taken into account for both dietary and physical activity recommendations. Most importantly, the total recommended pregnancy weight gain depends on pre-pregnant body weight, and weight issues should be addressed before pregnancy.

Future Direction for Research

It is reasonable to expect higher weight gain for multiple gestations. Recommendations for women carrying twins are given but more research should be done to precisely determine the total weight gain, as these ranges are wide. Also, the ranges for underweight women carrying twins is unknown. There was not enough information to recommend weight gain cutoffs and guidelines for women carrying three or more babies, women of short stature (<157 centimetres), and pregnant teens. Estimated energy requirements (EER) for overweight/obese women are unavailable so more research is needed to evaluate on that.

Practical Advice for Mothers

The following general tips can be helpful to pregnant women. It would be beneficial to maintain adequate physical activity to meet energy needs from the food consumed. Eating a balanced diet would be optimal for healthy pregnancy results. To prevent problems like dehydration and constipation, it is important to drink enough fluids, especially water, to support blood volume increases during pregnancy. It is recommended to accompany regular meals with a daily prenatal vitamin supplement that has sufficient folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...

 and iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...


If the fetus is predicted to have low birth weight, in addition to the general recommendations, it would be ideal to increase caloric intake, which can be done by having extra Food Guide Servings daily.
If the fetus is predicted to have high birth weight, smaller and more frequent meals should be consumed to allow better weight management. Moderate sugar intake, such as fruit juices, is also suggested. It is essential to limit food and beverages with high calories and salt content.
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