Large for gestational age
Encyclopedia
Large for gestational age (LGA) is an indication of high prenatal growth rate, often defined as a weight (or length, or head circumference) that lies above the 90th percentile for that gestational age
. Macrosomia, also known as big baby syndrome, is sometimes used synonymously with LGA, or is otherwise defined as a fetus or infant that weighs above 4000 gram
s (8 lb
13 oz
) or 4500 grams (9 lb 15 oz) regardless of gestational age.
, although fetal weight estimations late in pregnancy are quite imprecise.
There are believed to be links with polyhydramnios
(excessive amniotic sac
fluid).
(GD), as well as preexisting diabetes mellitus
(preexisting type 2 is associated more with macrosomia, while preexisting type 1 can be associated with microsomia). This increases maternal plasma glucose
levels as well as insulin
, stimulating fetal growth. The LGA newborn exposed to maternal DM usually has an increase only in weight. LGA newborns that have complications other than exposure to maternal DM present with universal measurements >90th percentile.
Other determining factors include:
The condition is most common in mothers of African origin, partly due to the higher incidence of diabetes.
. Such pregnancies often end in caesarean section
s in order to safely deliver the baby and to avoid birth canal lacerations. Upon birth, early feeding is essential to prevent fetal hypoglycemia
. Early diagnosis of individual problems is required.
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....
. Macrosomia, also known as big baby syndrome, is sometimes used synonymously with LGA, or is otherwise defined as a fetus or infant that weighs above 4000 gram
Gram
The gram is a metric system unit of mass....
s (8 lb
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
13 oz
Ounce
The ounce is a unit of mass with several definitions, the most commonly used of which are equal to approximately 28 grams. The ounce is used in a number of different systems, including various systems of mass that form part of the imperial and United States customary systems...
) or 4500 grams (9 lb 15 oz) regardless of gestational age.
Diagnosis
LGA is generally not diagnosed until after the birth, as the size and weight of the child is rarely checked during the latter stages of pregnancy. Babies that are large for gestational age throughout the pregnancy can sometimes be seen during a routine ultrasoundObstetric 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...
, although fetal weight estimations late in pregnancy are quite imprecise.
There are believed to be links with polyhydramnios
Polyhydramnios
Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in 0.2 to 1.6% of pregnancies,,...
(excessive amniotic sac
Amniotic sac
The 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,...
fluid).
Predetermining factors
One of the primary risk factors is poorly-controlled diabetes, particularly gestational diabetesGestational 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...
(GD), as well as preexisting diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
(preexisting type 2 is associated more with macrosomia, while preexisting type 1 can be associated with microsomia). This increases maternal plasma glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
levels as well as insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
, stimulating fetal growth. The LGA newborn exposed to maternal DM usually has an increase only in weight. LGA newborns that have complications other than exposure to maternal DM present with universal measurements >90th percentile.
Other determining factors include:
- Gestational age; pregnancies that go beyond 40 weeks increase incidence
- Fetal sex; male infants tend to weigh more than female infants
- Genetic factors; taller, heavier parents tend to have larger babies, with an obeseObesityObesity 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...
mother greatly increasing the chances - Excessive maternal weight gain
- Multiparity (have 2-3x the number of LGA infants vs. primaparas)
- Congenital anomalies (transposition of great vessels) - Hydrops FetalisHydrops fetalisHydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion are an accumulation of excessive fluid in the allantoic or amniotic space respectively.-Presentation:Locations can...
- Erythroblastosis fetalis - Hydrops FetalisHydrops fetalisHydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion are an accumulation of excessive fluid in the allantoic or amniotic space respectively.-Presentation:Locations can...
- Use of some antibiotics (amoxicillinAmoxicillinAmoxicillin , formerly amoxycillin , and abbreviated amox, is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral...
, pivampicillinPivampicillinPivampicillin is a pivaloyloxymethylester of ampicillin. It is a prodrug, which is thought to enhance the oral bioavailability of ampicillin because of its greater lipophilicity compared to that of ampicillin.-Adverse effects:...
) during pregnancy - Hydrops FetalisHydrops fetalisHydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion are an accumulation of excessive fluid in the allantoic or amniotic space respectively.-Presentation:Locations can... - Genetic disorders of overgrowth (e.g. Beckwith-Wiedemann syndrome, Sotos syndrome)
The condition is most common in mothers of African origin, partly due to the higher incidence of diabetes.
Treatment
Depending upon the relative size of the head of the baby and the pelvic diameter of the mother vaginal birth may become complicated. One of the most common complications is shoulder dystociaDystocia
Dystocia is an abnormal or difficult childbirth or labour. Approximately one fifth of human labours have dystocia.Dystocia may arise due to incoordinate uterine activity, abnormal fetal lie or presentation, absolute or relative cephalopelvic disproportion, or a massive fetal tumor such as a...
. Such pregnancies often end in 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...
s in order to safely deliver the baby and to avoid birth canal lacerations. Upon birth, early feeding is essential to prevent fetal hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
. Early diagnosis of individual problems is required.