CHICAGO, June 18 (Xinhua) -- The risk of early-onset neonatal bacterial sepsis increases with maternal obesity, according to a study posted on the website of the University of Michigan (UM) on Wednesday.

The researchers 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.

The researchers then resort to sibling comparisons that 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 6 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," said Eduardo Villamor, a professor of epidemiology at UM's School of Public Health.

The researchers mapped 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're born before term, their immune system might be immature because it didn't 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."

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.

"Until now, there was not a clear clinical reason to do it, but it was a practice based on lab studies that showed that due to the obesity the antibiotics might not reach the concentration needed to be effective," Villamor said. "This work contributes strong evidence as to why doctors should really consider increasing the antibiotic dose when they have to do preoperatory prophylaxis on a mother with obesity."

The study, jointly conducted by UM and the Karolinska Institute in Sweden, has been published in Clinical Infectious Diseases. Enditem

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