Obesity & Fetal Brain Development

By Eva Martin, MD of Elm Tree Medical, Inc.

We’ve all heard about the “obesity epidemic” in America and about the increased risks associated with maternal obesity in pregnancy. But, a new body of research is uncovering risks of obesity that go beyond the infant’s risk for metabolic disorders and affect the infant’s brain development. Pregnancy is arguably the most important time period for neural development, and the ways in which maternal obesity and excessive weight gain in pregnancy can affect neural development are alarming.

In the United States, obesity affects 35% of women of reproductive age. 60% of reproductive age women are overweight. Given that this condition affects the majority of women who could potentially become pregnant, it is of the utmost importance to understand the effects maternal weight can have on the developing fetus’s brain.

First, a disclaimer. All of the research is from epidemiological studies. Obviously, it would be unethical to force a group of pregnant women to gain an unhealthy amount of weight in pregnancy to study what the effects are in a randomized clinical trial. So, we are left with good, large population studies that control for possible confounders.

Using epidemiology studies, researchers have found links between maternal obesity and/or excessive weight gain in pregnancy and multiple conditions: cognitive deficits, lower IQ, autism spectrum disorders, attention deficit disorders, and cerebral palsy. Maternal obesity was linked to a 1.3 to 3.6 fold increase in cognitive deficits. For every increase in BMI, researchers found that children’s IQ was incrementally lower. Compared to non-obese women’s children, obese women’s children had 2- to 5-point lower IQ scores.

Controversy surrounds the purported contributors to the development of autism spectrum disorders (ASD). However, most studies have found that higher maternal BMI is linked to a higher risk of being diagnosed with ASD in childhood. Two studies did not show an association between pre-pregnancy BMI and future ASD diagnosis. However, these studies showed an association with high weight gain in pregnancy and ASD risk.  Interestingly, one study also showed a connection between paternal obesity and increased risk of ASD.

Similar to the dose-dependent relationship between BMI and IQ, each increase in maternal pre-pregnancy BMI has been linked to more ADHD symptoms in offspring. Compared to non-obese women, obesity confers a 2.8-fold increased risk of ADHD.

Similarly, increased maternal BMI is also linked to increasing risk of cerebral palsy. Children of overweight mothers have a 1.2 times increased odds of cerebral palsy, and children of obese mothers have a 3.0 times increased odds. For each increase in 1 BMI unit, the risk of cerebral palsy increases 7%.

What mechanisms could possibly cause these alarming findings? The most popular theory is that obesity induces inflammation, which affects fetal neural programming. Tests have shown that obese women have higher levels of inflammatory markers in their blood, and these inflammatory agents have been linked to neonatal gene expression in the brain. Experts also opine that varying levels of nutrients or hormones could explain the effects. Signaling from hormones like leptin, serotonin, and dopamine have been shown to go awry.

While this research is certainly concerning, the main point is to highlight the importance of supporting mothers in maintaining a healthy weight before pregnancy and gaining a healthy amount of weight during pregnancy. More resources should go towards programs to aid women in this pursuit. This research goes to show- dollars spent investing in women’s health will pay off for generations to come. It also highlights a place for more research into potential therapeutics- like Omega 3 fatty acids, which have shown promise.

We want to hear from you! How do you encourage healthy weight management in your patients before, during, and after pregnancy? What programs would have the most impact in helping reproductive age women?