Risk factors and adverse pregnancy outcomes in small-for-gestational-age births

Abstract: The studies were undertaken to evaluate risk factors and outcomes in small-for-gestational-age (SGA) births, in cohort studies using the population-based Swedish Birth, Twin and Education Registers. A cohort study of pregnant women from Uppsala County evaluated the effect on birthweight by caffeine. Maternal anthropometrics influence risks of SGA at all gestational ages. Smoking increases risks of moderately preterm and term SGA, while hypertensive disorders foremost increase the risk of preterm SGA. Monozygotic twin mothers have higher concordance rates in offspring birthweight-for-gestational length than dizygotic twin mothers, indicating genetic effects on fetal growth. Caffeine is not associated with a reduction in birthweight or birthweight-for-gestational age. The increased risk of stillbirth in postterm pregnancies is explained by increased rates of SGA in postterm pregnancies. Births with malformations account for a large part of the SGA-related increased risk of infant death. SGA, as defined by an individualised birth-weight standard, is a better predictor of adverse pregnancy outcomes than the commonly used population-based birthweight standard. Risk factors for SGA, as well as the prognosis for the SGA infant, vary with gestational age. However, the commonly used definition of SGA is probably a poor predictor of intrauterine growth retardation.