Born Large for Gestational Age: Bigger Is Not Always Better.

D uring the past 60-90 years, there has been a change in the growth trajectories of large for gestational age (LGA) babies and the associated health effects later in life. Subjects classified as large at birth in the 1920s were found to have reduced morbidity and mortality in their seventh decade compared with those born of lower birth weight. Indeed, across the birth weight range there was a progressive increase in cardiovascular and metabolic risk with a decrease in birth weight, even among those in the normal range. These findings suggested that, historically, larger size at birth provided metabolic advantages that contributed to improved health and possibly longevity. Long-term outcomes in those born LGA have dramatically changed in the last 30 years, with LGA being now associated with early obesity and increased cardiovascular and metabolic risk. The association between birth weight and the risk of later adult diseases currently seems to be U-shaped. It is likely that this relatively recent increased risk of adult disease in those born large is related to the underlying factors influencing fetal growth as well as changes in postnatal environmental conditions. For instance, from 1910 to the late 1940s, events including the World Wars and the Great Depression were characterized by limited available nutrition to the wider population. Thus, in the past, babies were much less likely to be overnourished in utero, as shown by lower maternal weight gain and overweight/obesity rates during pregnancy, so that LGA babies were more likely to have been long and lean. Much greater rates of postterm births and increased sibship may represent risk factors for lean LGA babies. Before active obstetric intervention to avoid prolonged pregnancies, the postterm birth rate was 10% compared with approximately 3% currently. Conversely, there has been a nutritional excess in utero in recent decades, leading to LGA neonates that are long and fat, with postnatal exposure to an “obesogenic” environment responsible for a further acceleration in growth.