Determinants of morbidity in late preterm infants

Objective: To assess the effect of selected maternal medical conditions and complications of pregnancy on the risk for morbidity among late preterm neonates. Design: Prospective cohort study. Material and methods: A total of 548 late preterm neonates (34(0/7) to 36(6/7) weeks' gestation) delivered from August 2006 to July 2009, were included. Information regarding demographics, gestational age, mode of delivery, maternal age and parity, pre-existing medical conditions and complications of pregnancy were obtained and associated with neonatal morbidity, both independently and as joint exposures. Newborn morbidity was defined by combining specific diagnoses, length of hospital stay, and transfer to the Neonatal Intensive Care Unit. Results: Overall, 165 (30.1%) of the late preterm infants suffered from morbidity. The morbidity rates were 16.8% at 36 weeks' gestation, and then approximately doubled from 38.2% at 35 weeks to 59.7% at 34 weeks. The joint effect of gestational age (OR 8.43 for 34 weeks and 3.60 for 35 weeks' gestation), small for gestational age (SGA) (OR 4.18), multiple gestation (OR 3.68) and lack of antenatal steroid administration (OR 4.03), was greater than the independent effect of each of these factors, and greater than additive. Emergency caesarean section (OR 1.43) and antepartum haemorrhage (OR 3.07) were also associated with a significant impact on neonatal morbidity. Conclusions: The risk for morbidity among late preterm infants, changes with each passing week of gestation. This risk seems to be intensified, when other exposures such as SGA, multiple gestation, emergency caesarean section, lack of antenatal steroid administration and antepartum haemorrhage, are also present. (c) 2010 Elsevier Ireland Ltd. All rights reserved.