Infant Mortality

An increased risk found for infant mortality due to necrotizing enterocolitis (NEC) from mothers’ smoking during pregnancy. The correlation was found to be higher amongst babies that were white and female.


The mortality rate due to necrotizing enterocolitis (NEC) is between 15-25% and represents the leading cause of infant mortality in neonatal babies. NEC may result from 1) intestinal walls being too thin and rupturing due to underdevelopment, 2) circulatory problems leading to the dying off of patches of the wall, and/or 3) an underdeveloped immune system leading to an overgrowth of bacteria, which eat through the walls and enter the bloodstream. The causes of NEC are not fully understood, but there are indications that low-oxygen brain injury, use of formula milk, and bacterial infection of the colon are contributing factors for babies born premature. While it is well known that smoking while pregnant is harmful to the fetus, current epidemiological data that connects maternal smoking with NEC is sparse and concludes either no correlation or a negative relationship.

The authors of this novel study, published in Scientific Reports, hypothesized that smoking increases the risk of death in NEC-affected premature babies. The study was conducted using data that was initially collected from the US Linked Livebirth and Infant Death files from 2000 to 2004, and processed by the National Center for Health Statistics and the US Centers for Disease Control and Prevention. The data contained demographic information of the mothers, obstetric history, smoking, birth outcomes, infant death, and the underlying cause of death. The final dataset for analysis was 1,315,493 births. Among the women that smoked during pregnancy, those that smoked fewer than ten cigarettes per day were categorized as light smokers, and those that smoked ten or more per day as heavy smokers.  When compared to non-smoking mothers, the odds that light and heavy smokers had a higher risk of NEC-associated infant mortality was higher (1:1.21 and 1:1.30, respectively). The association for NEC-associated infant mortality was also higher among white (light smoking 1:1.69 and heavy smoking 1:1.44) and female (light smoking 1:1.31 and heavy smoking 1:1.62) babies.

The main limitations in the study involve the self-reporting of smoking on the birth certificates and the variability in breast feeding, Due to the stigma regarding smoking while pregnant, it may be that some mothers may have been reluctant to accurately disclose this. Breast feeding has been shown to have a dose-response in lowering incidence of NEC.


Written By: Kenneth Dominguez, PhD

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