Impact of fetal growth restriction on mortality and morbidity in a very preterm birth cohort

Objective: To assess the impact of being small for gestational age (SGA) on very preterm mortality and morbidity rates by using different birthweight percentile thresholds and whether these effects differ by the cause of the preterm birth.

Study design: The study included singletons and twins alive at onset of labor between 24 and 31 weeks of gestation without congenital anomalies from the Models of Organising Access to Intensive Care for very preterm births very preterm cohort in 10 European regions in 2003 (n = 4525). Outcomes were mortality, intraventricular hemorrhage grade III and IV, cystic periventricular leukomalacia, and bronchopulmonary dysplasia (BPD). Birthweight percentiles in 6 classes were analyzed by pregnancy complication.

Results: The mortality rate was higher for infants with birthweights <25th percentile when compared with the 50th to 74th percentile (adjusted odds ratio, 3.98 [95% CI, 2.79-5.67] for <10th; adjusted odds ratio, 2.15 [95% CI, 1.54-3.00] for 10th-24th). BPD declined continuously with increasing birthweight. There was no association for periventricular leukomalacia or intraventricular hemorrhage. Seventy-five percent of infants with birthweights <10th percentile were from pregnancies complicated by hypertension or indicated deliveries associated with growth restriction. However, stratifying for pregnancy complications yielded similar risk patterns.

Conclusions: A 25th percentile cutoff point was a means of identifying infants at higher risk of death and a continuous measure better described risks of BPD. Lower birthweights were associated with poor outcomes regardless of pregnancy complications.