Patterns and success of fetal programming among women with low and extremely low pre-pregnancy BMI

To estimate the frequency of fetal programming phenotypes among women with low BMI and the success of these programming patterns-to determine if small for gestational age (SGA) is a biologically adaptive mechanism to improve chances for infant survival. We examined the frequency of fetal programming phenotypes: SGA, large for gestational age (LGA), and adequate for gestational age (AGA) among 1,063,888 singleton live births from 1978 to 1997. We also estimated the success of fetal programming phenotypes using neonatal death as the primary study outcome. Underweight gravidas with AGA and LGA babies had elevated risk of neonatal mortality when compared to normal weight mothers, while the risk for neonatal mortality among mothers with SGA babies was reduced. The variation in relative degrees of fetal programming patterns and success observed suggests that underweight mothers are more likely to succeed in programming SGA fetuses rather than any other phenotype.