Study Finds Strong Link Between Pre-Pregnancy Obesity, Infant Deaths

January 20, 2016

BOSTON -- January 20, 2016 -- Pre-pregnancy obesity is strongly associated with infant mortality, and compliance with weight-gain guidelines during pregnancy has a limited impact on that mortality risk, according to a study published online in the journal Obstetrics and Gynecology.

The study is the largest to date of the relationship between pre-pregnancy obesity, prenatal weight gain and infant mortality.

Eugene Declercq, MD, Boston University School of Public Health, Boston, Massachusetts, and colleagues used birth and death records of more than 6 million newborns in 38 states from 2012 to 2013, which included information on the mother's height and pre-pregnancy weight, needed to compute body mass index (BMI).

The authors examined overall infant mortality in 3 major categories: infants who died from preterm-related causes, congenital anomalies, and sudden unexpected infant death.

Results showed that infant mortality rates from preterm causes increased at higher BMIs, with rates twice as high for obese women (ie, ≥79 kg for a woman 5’4” tall) than for normal-weight women (49-65 kg at 5’4”). Deaths from congenital anomalies and sudden infant death also were higher among babies born to obese mothers. Mortality rates rose consistently across obesity categories.

Compared with babies born to women with normal pre-pregnancy weights, the risk of infant death was 32% higher for mothers in the obese 1 category and 73% higher for those in the obese 3 category, even after controlling for demographic and medical risk factors.

Dr. Declercq said the findings support the importance of clinicians and public health officials addressing the issue of obesity before pregnancy begins, and the need for more research into the underlying processes that might link pre-pregnancy obesity and poor infant outcomes.

“The findings suggest that primary care clinicians, ob-gyns and midwives need to have conversations about weight as part of well-woman care and when women are contemplating getting pregnant,” said Dr. Declercq. “There is a need for more open, honest discussions about avoiding the possible risks of maternal obesity on infant health.”

The researchers also found a general lack of adherence to guidelines issued by the Institute of Medicine in 2009, particularly among women in the overweight and obese 1 categories. The guidelines recommended weight gain of 5 kg to 9 kg (11-20 lbs) for mothers with a pre-pregnancy BMI in the obese range.

Further, when mothers’ weight gain was within the recommended range, there was limited impact on infant mortality rates.

Dr. Declercq noted that the focus of the guidelines was not solely the reduction of infant mortality.

“These findings suggest that 60% to 75% of mothers aren’t following the guidelines -- and even when they do, adherence does little to lower infant mortality,” he said.

SOURCE: Boston University Medical Center

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