The implications of late-preterm birth for global child survival

Risks associated with late-preterm birth The article by Gouyon et al. in this issue adds to a limited collection on the health of late-preterm infants. Using a population-based dataset of over 150 000 singletons born alive at 34–41 weeks gestation in Burgundy in 2000–08, the authors showed a serial reduction with gestational age in the risk of death or severe neurological condition, from an adjusted relative risk of 6.8 [95% confidence interval (CI) 4.1–11.1] at 34 weeks to a comparative nadir at 39–41 weeks. There was a reduction in respiratory disorders requiring oxygen and either continuous or intermittent positive airway pressure support, from a relative risk of 61.0 (95% CI 54.1–86.9) at 34 weeks. They also found higher risks for infants born at 37 and 38 weeks than for later term infants, suggesting that our view of term as running from 37 to 41 weeks could be more nuanced. The findings are broadly similar to those of Shapiro-Mendoza et al., who used US certification data to compare 26 170 late-preterm with 377 638 term infants. The risk of morbidity doubled for each week of birth earlier than 38 weeks, with a relative risk of 20.6 (95% CI 19.7–21.6) for infants born at 34 weeks. A population-based Canadian study of 88 867 live-born infants showed a relative risk of respiratory morbidity of 4.4 (95% CI 4.2–4.6) and of infection of 5.2 (95% CI 4.6–5.9) in late-preterm compared with term infants. Preterm infants born in the later weeks of pregnancy are a relatively under-researched group. Preterm labour is generally no coincidence, and infants born early differ systematically from those born at term. The maternal morbidities documented by Gouyon et al. attest to this (24% of mothers of infants born at 34 weeks had two or more defined antenatal complications, compared with 2% of mothers of infants born at 39–41 weeks), as does the fact that 17% of 34-week infants were small for gestational age; by definition, 10% should be. Additionally, the increased risk is not explained by congenital abnormalities. In 2007, Engle et al. proposed that we move towards an explicit acknowledgment of the potential problems, defining late-preterm as from 34 to 36 weeks after the beginning of a mother’s last menstrual period (or 239–259 days inclusive). Late preterm infants are more likely to experience illness than term infants, particularly as a result of thermal instability, hypoglycaemia, respiratory distress, apnoea, jaundice and feeding difficulties.