Macrosomia

Large for gestational age
LGA: A healthy 11-pound (5.0 kg) newborn child, delivered vaginally without complications (41 weeks; fourth child; no gestational diabetes)
Classification and external resources
Specialty	pediatrics
ICD-10	P08
ICD-9-CM	766
DiseasesDB	21929
MedlinePlus	002251
eMedicine	med/3279
MeSH	D005320
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Large for gestational age (LGA) is an indication of high prenatal growth rate.

LGA is often defined as a weight, length, or head circumference that lies above the 90th percentile for that gestational age. However, it has been suggested that the definition be restricted to infants with birth weights greater than the 97th percentile (2 standard deviations above the mean) as this more accurately describes infants who are at greatest risk for perinatal morbidity and mortality.

Macrosomia, which literally means "big body," is sometimes confused with LGA. Some experts consider a baby to be big when it weighs more than 8 pounds 13 ounces (4,000 g) at birth, and others say a baby is big if it weighs more than 9 pounds 15 ounces (4,500 g). A baby is also called “large for gestational age” if its weight is greater than the 90th percentile at birth.

It is important to note that LGA and macrosomia cannot be diagnosed until after birth, as it is impossible to accurately estimate the size and weight of a child in the womb. Babies that are large for gestational age throughout the pregnancy may be suspected because of an ultrasound, but fetal weight estimations in pregnancy are quite imprecise. For non-diabetic women, ultrasounds and care providers are equally inaccurate at predicting whether or not a baby will be big. If an ultrasound or a care provider predicts a big baby, they will be wrong half the time.

Although big babies are only born to 1 out of 10 women, the 2013 Listening to Mothers Survey found that 1 out of 3 American women were told that their babies were too big. In the end, the average birth weight of these suspected “big babies” was only 7 pounds 13 ounces (3,500 g). In the end, care provider concerns about a suspected big baby were the 4th most common reason for an induction (16% of all inductions), and the 5th most common reason for a C-section (9% of all C-sections). Unfortunately, this treatment is not based on current best evidence.

In fact, research has consistently shown that, as far as birth complications are concerned, the care provider’s perception that a baby is big is more harmful than an actual big baby by itself. In a 2008 study, researchers compared what happened to women who were suspected of having a big baby to what happened to women who were not suspected of having a big baby—but who ended up having one. In the end, women who were suspected of having a big baby (and actually ended up having one) had a triple in the induction rate; more than triple the C-section rate, and a quadrupling of the maternal complication rate, compared to women who were not suspected of having a big baby but who had one anyway.

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Wikipedia