New Research Finds Link Between Maternal Obesity and HIE

New research finds that maternal obesity in early pregnancy is associated with an increased risk of birth asphyxia (hypoxic-ischemic encephalopathy) and cerebral palsy. These new findings highlight the importance of informing mothers about potential birth-related complications and risks.

Maternal Obesity, HIE and Cerebral Palsy
Researchers from the University of Michigan and Sweden’s Karolinska Institute found that not only does being obese or overweight increase a child’s risk of cerebral palsy, but the heavier the mother, the greater the risk.

According to Eduardo Villamor, University of Michigan professor of epidemiology, “Each degree of obesity severity during pregnancy increased the chances a child would be diagnosed with cerebral palsy…Compared with women of normal weight, women with overweight had a 22 percent higher rate, whereas women with severe obesity had more than twice (more than 100 percent increase) the rate.” As a reference, women considered ‘overweight’ have a BMI of 25 to 29.9; obesity falls into the range of BMI 30+.

According to Villamor and colleagues, maternal obesity increases the risk of neonatal asphyxia (also known as hypoxic-ischemic encephalopathy), highlighting the risks specifically in term births. They also stress that one of the factors with largest associated risk for cerebral palsy is a low Apgar score (<7) at 5 minutes. They found that asphyxia-related neonatal morbidity mediated about 45% of the connection between maternal BMI and cerebral palsy rates in full-term children.

This research is a landmark paper because it is one of the first studies to analyze data using an entire country as its studied population. The team analyzed more than 1.4 million birth records of Swedish children between 1997 and 2011, tracking maternal weight during early pregnancy. They then conducted follow-up on the children from birth to either (1) age of a cerebral palsy diagnosis, (2) death, or (3) the end of the follow-up period in 2012.

Villamor and colleagues have previously also studied the association of excess maternal weight with increased risk of preterm birth, asphyxia-related birth complications and congenital malformations.

Why is the Link Between Maternal Obesity and Birth Asphyxia (HIE)-Related Complications So Important?

According to Villamor and colleagues, “…The association is of public health relevance due to the large proportion of women with overweight or obesity worldwide…The number of women with a BMI of 35 kg/m2 or more globally doubled from approximately 50 to 100 million from 2000 through 2010. In the United States, approximately half of all pregnant women have a diagnosis of being overweight or obese at the first prenatal visit. Considering the high prevalence of obesity and the continued rise of its most severe forms, the finding that maternal overweight and obesity are related to rates of cerebral palsy in a dose-response manner may have serious public health implications.”

While a high percentage of women in the United States may be overweight or obese, a fairly low percentage (between 20-40%) of pregnant women actually receive weight-related counseling from their primary care providers. Women should be appropriately counseled by their care providers regarding risks to their health and the health of their babies, especially when it comes to complications like hypoxic-ischemic encephalopathy that can cause permanent lifelong injuries like cerebral palsy.

The Takeaway

Hypoxic-ischemic encephalopathy risks are mediated by many preventable factors, with obesity being one of the largest. Medical care providers should be having conversations about healthy weight before and during pregnancy with their patients.

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