Maternal smoking during pregnancy may increase infant mortality due to NEC
Maternal smoking during pregnancy appears to contribute to an increase in the risk of necrotizing enterocolitis (NEC)-specific mortality in premature infants, especially those who are female and white, a study suggests.
The population-based cohort study included 1,315,493 eligible singletons, live preterm babies. There were 1,122 NEC-associated deaths (<1 year of age), with the majority (82.7 percent) occurring in the late neonatal period (7 to 27 days after birth), corresponding to a mortality rate of 8.5 per 10,000 live births.
Maternal smoking during pregnancy were classified into three categories: nonsmoking, light smoking (average of <10 cigarettes/day) and heavy smoking (average of ≥10 cigarettes/day). Logistic regression analyses, with adjustment for potential confounders, were performed to test the association between prenatal smoking and NEC-associated infant mortality rates
Compared with nonsmoking, light and heavy smoking during pregnancy increased the odds of NEC-associated infant mortality by 21 percent (95 percent CI, 1.03 to 1.43) and 30 percent (1.12 to 1.52), respectively. The effect of smoking on NEC-associated infant mortality was more pronounced among infants with white race (light smoking: adjusted odds ratio [aOR], 1.69; 1.34 to 2.13; heavy smoking: aOR, 1.44; 1.18 to 1.75) and female gender (light smoking: aOR, 1.31; 1.02 to 1.69; heavy smoking: aOR, 1.62; 1.29 to 2.02).
The current study demonstrates that maternal smoking, both light and heavy, during pregnancy may increase the risk of mortality in premature infants due to NEC. “[This] may have implications in basic and epidemiologic research on the mechanisms that underlie NEC-associated development and death.”
The most common gastrointestinal emergency in neonates, NEC is an important cause of morbidity and mortality in neonates, with the mortality rate of between 15 and 25 percent remaining stable in the last 30 years. Factors such as hypoxic-ischaemic injury, feeding with formula milk and colonization by pathological bacteria are generally considered to contribute to the development of NEC. The risk is further increased by prematurity and low birthweight due to developmental immaturity of key functions such as intestinal function, circulatory regulation and immune defense in these infants. [Lancet 2006;368:1271–1283; Annu Rev Med 2009;60:111–124; Neonatology 2009;96:203–10; Semin Fetal Neonatal Med 2011;16:145–150]