Outcome of small for gestational age preterm singletons: a population-based cohort study.

OBJECTIVE: To examine the outcomes of births among small and appropriate for gestational age (SGA and AGA) infants by gestational age and maternal characteristics.

MATERIALS AND METHODS: We used a national perinatal registry to compare the selected maternal and neonatal outcomes between AGA and SGA neonates born at gestational age groups 33-36, 30-32, 28-29, and <28 weeks. We evaluated maternal body mass index (BMI), pre-gestational/gestational diabetes, hypertensive disorders, and cesarean births as well as frequencies of 5-min Apgar score <7, intraventricular hemorrhage (IVH), respiratory distress syndrome (RDS), the need for assisted ventilation, and early neonatal deaths.

RESULTS: We evaluated 159,774 AGA (8871 preterm) and 13,735 SGA (1147 preterm) infants and found a gradual decrease in the incidence of SGA infants with increasing gestational age. Diabetes was unrelated to having an SGA or AGA infant among preterm births, but the odds ratio (OR) for preeclampsia among preterm-SGA pregnancies was up to 6.9 (95% CI 3.8, 12.5) at <28 weeks. SGA infants fare worse compared to AGA neonates in every parameter tested but only in preterm births >30 weeks.

CONCLUSIONS: Being SGA further complicates preterm births after 30 weeks of gestation but not earlier. This might suggest that an extended period in the hostile intrauterine environment, or that being born at <30 weeks, is bad enough and is not further aggravated by being SGA.