Maternal obesity linked to increased risk of early-onset neonatal sepsis

June 23, 2020

The risk of early-onset neonatal bacterial sepsis increases with maternal obesity, according to a new study from the University of Michigan and the Karolinska Institute in Sweden. Lead researcher Eduardo Villamor, a professor of epidemiology at U-M’s School of Public Health, said the study builds on previous research into exposure to motherly obesity and health risks to the baby. The study has been published in Clinical Infectious Diseases.

“We found that maternal obesity is related to adverse pregnancy outcomes and to some adverse developmental outcomes for the children, such as cerebral palsy and epilepsy,” Villamor said. “Now we found that maternal obesity is also related to increased risk of early-onset neonatal bacterial sepsis.

Villamor and colleagues used a nationwide population-based retrospective cohort of about 1.9 million live singleton infants born in Sweden between 1997 and 2016. The infants were followed through their first three days of life for a culture-confirmed sepsis diagnosis. Mothers were categorized per weight (BMI). The researchers also considered co-variables such as maternal age, country of origin, education level, cohabitation with a partner, smoking during pregnancy and year of delivery.

Villamor said sibling comparisons offered a unique opportunity to enhance causal inference by controlling associations for confounders shared within families.

“In the comparison among siblings, we found that when a child had had sepsis, the mother had a higher BMI before pregnancy than when she gave birth to the baby that did not have sepsis. One extra BMI unit between pregnancies, which is equivalent to about six pounds for a woman of average height and weight in this population, would translate into an 8 percent increase in risk of sepsis for the baby.”

Villamor said they were able to map out how the risk process might lead from the mother having obesity to the child having sepsis. Maternal obesity increases the risk of preeclampsia, which leads to an emergency cesarean section. Often, preeclampsia happens before term.

“If you have a combination of these events, that could explain about 50 percent of the potential effect of maternal obesity on sepsis,” Villamor said. “The babies of preeclamptic mothers have fewer bacteria-fighting cells in their blood, so they might be more likely to get infected. If they are born before term, their immune system might be immature because it did not have time to develop in utero. And if the mother undergoes emergency C-section, that also puts them at a higher risk of infection because it is an emergency surgical procedure.”

Villamor said the research may also point to a clinical solution to prevent sepsis among newborns: when mothers with obesity need an emergency C-section, they might benefit from a higher dose of prophylactic antibiotics than what is usually prescribed.

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