Maternal Obesity Alone May Increase Neonatal Risks

Marlene Busko

September 19, 2018

In a cohort of pregnant women without diabetes or hypertension, those who were obese had an increased risk of having a newborn with complications, researchers report.   

Specifically, obese women had an increased risk of having a new baby who had hypoxic-ischemic encephalopathy or suspected sepsis or who needed to undergo hypothermia.

The study by Brock E. Polnaszek, MD, from Washington University, St. Louis, Missouri, and colleagues was published online in Obstetrics & Gynecology.

Earlier work has suggested that "obesity may be as important, if not more important, than hypertension and diabetes as a potentially modifiable risk factor for clinicians to target to improve neonatal outcomes," the researchers write.

The current study suggests that in newborns of obese pregnant women, clinicians "should watch for" suspected sepsis or hypoxic-ischemic encephalopathy (a brain injury because of lack of oxygen) and should consider the use of hypothermia to cool the neonate's head or body in cases of hypoxic-ischemic encephalopathy, Polnaszek told Medscape Medical News in an email.

Maternal obesity is "not currently included when we identify an infant as high risk for sepsis," he continued, hinting that it perhaps should be.

"Our study suggests that maternal obesity alone may be an important factor for clinicians to consider when interpreting American Academy of Pediatrics data" for suspected sepsis, he and his colleagues write.

When counseling obese pregnant women, Polnaszek said, clinicians should inform them of their increased risk of complications.  

The American College of Obstetricians and Gynecologists recommends that obese women gain only 11 to 20 pounds (5 to 9 kg) during pregnancy (compared with 25 to 35 pounds [11.3 to 15.9 kg] for normal-weight women), he noted.

And one recent study has even suggested that very obese women should be counseled to lose weight during pregnancy.

Obesity in Pregnancy a Standalone Risk?

Pregnant obese women may also have diabetes and hypertension, but most (65% to 85%) do not have these comorbidities, the researchers explain by way of background.

Obesity on its own may lead to poor neonatal outcomes, they add, because it is "a proinflammatory, pathophysiologic state [and] it is possible that this condition may alter the intrauterine environment of the developing fetus leading to adverse neonatal outcomes."

To investigate this association, Polnaszek and colleagues performed a secondary analysis of data from a cohort of 8580 pregnant women enrolled in a prospective study at their center in 2010 to 2014.

After excluding 2122 women who had hypertension (including gestational hypertension, eclampsia, and pre-eclampsia), diabetes (including gestational diabetes), or both, or missing data, this left 6458 women for the current analysis.

Of these women, 3311 were obese and 3147 were not.

Obese women were older (mean age 25.7 vs 25.2 years) and more likely to be African American (69% vs 58%) or have a prior cesarean delivery (10% vs 7%).

And in the pregnancy under investigation, the obese women were more likely to have a cesarean delivery (19% vs 12%), be induced, or have a prolonged labor compared with those who were not obese.

The study's two coprimary outcomes were:

  • Neonatal morbidity (a composite of death, mechanical ventilation, respiratory distress, meconium aspiration, suspected sepsis, confirmed sepsis, hypoxic-ischemic encephalopathy, therapeutic hypothermia, and seizures).

  • Neonatal neurologic morbidity (a composite of hypoxic-ischemic encephalopathy, therapeutic hypothermia, and seizures).

After adjusting for race, newborns of obese women versus nonobese women had a significantly higher risk of neonatal morbidity (9.2% vs 7.2%, odds ratio [OR], 1.39) and neonatal neurologic morbidity (0.7% vs 0.3%; OR, 2.84).

Drilling deeper revealed that the newborns of obese women were more likely to have hypoxic-ischemic encephalopathy (0.5% vs 0.2%; OR, 2.80) and receive hypothermia treatment (0.6% vs 0.2%; OR, 2.92).

Although they were also more likely to have suspected sepsis (7.6% vs 5.8%; OR, 1.45), they were equally likely to have confirmed sepsis (0.1% vs 0.1%).

Three neonates died (two in one group and one in the other, which was not significantly different).

Need Ways to Lower Neonatal Morbidity in Obese Pregnant Moms

Neonatal hypoxic-ischemic encephalopathy is mainly caused by systemic hypoxemia and/or reduced cerebral blood flow, Polnaszek explained.

In full-term infants with moderate to severe hypoxic-ischemic encephalopathy, "mild induced hypothermia significantly improves survival and disability...and current hypothermia protocols [recommend] starting treatment within the first 6 hours of life."

And sepsis in neonates, Polnaszek noted, "is a critical diagnosis to make and one not to miss as it is often high stakes and high rewards if treated appropriately," whereas, "left untreated, it may lead to neonatal death."

"Future studies are needed," the authors conclude, "to corroborate and identify strategies to reduce neonatal morbidity with the increasing number of women with obesity."

The study was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and Robert Wood Johnson Foundation. The authors have reported no relevant financial disclosures.

Obstet Gynecol. Published online August 17, 2018. Abstract

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