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A new study published in the Journal of Child Psychology and Psychiatry looked at maternal prenatal body mass index (BMI) and human fetal brain development.

“Given knowledge that the physical well-being of a mother during pregnancy is important for the long-term brain health of her child, we sought to discover whether and how maternal body mass index may relate brain development in the womb,” senior study author, Dr. Moriah E. Thomason told us. “It was already known that maternal prenatal BMI related to cognitive and regulatory problems in childhood, but the neural correlates and their early developmental origins had yet to be addressed.”

According to the Centers for Disease Control and Prevention, if a woman was underweight before pregnancy with a BMI of less than 18.5, a healthy weight gain during pregnancy should range between 28 and 40 pounds. If a woman had a normal weight before pregnancy with a BMI of between 18.5 and 24.9, a healthy weight gain during pregnancy should range between 25 and 35 pounds.

“We had a theory but also took a largely data-driven approach in order to be as impartial as possible,” Dr. Thomason told us. “We confirmed that brain areas linked to adult obesity are the areas where we observed significant effects of the fetus in utero.”

If a woman was overweight before pregnancy with a BMI of 25 to 29.9, a healthy weight gain during pregnancy should range between 15 and 25 pounds. If a woman was obese before pregnancy with a BMI of greater than or equal to 30, a healthy weight gain during pregnancy should range between 11 and 20 pounds.

“Prior studies provide evidence of cognitive delays in children born to high BMI mothers, but until now it has been difficult to attribute those differences to neural processes with prenatal onset,” Dr. Thomason told us. “For example, it is difficult to disentangle the influence of the postnatal environment on brain health and development in that child. We had been operating under the assumption that programming occurs during pregnancy to influence that child’s brain with lasting consequence, but we lacked evidence.” 

Prior studies also show that only one third of pregnant women gained the recommended amount of weight during pregnancy. Forty-eight per cent of women in the United States gained too much weight during pregnancy while 21 per cent gained too little during pregnancy. Thirty-two per cent of pregnant woman stayed within the recommended weight range.

The CDC recommends speaking with a health care provider, tracking pregnancy weight, eating a balanced diet, limiting sugars and solid fats, knowing your calorie needs, and doing 150 minutes of moderate intensity aerobic activity per week to help keep within the recommended weight for pregnancy.

“We used resting-state MRI, a non-invasive technology, that utilizes information from spontaneous activity of the brain to construct circuits based on coordinated fluctuations in that data over time,” Dr. Thomason told us. “We sought to identify where the strength of connectivity (in the resulting circuits) showed differences related to maternal BMI.”

Dr. Thomason and the research team discovered that connectivity in frontal and insula circuits varied with maternal BMI. Dr. Thomason believes it is noteworthy that the significant fetal neural effects obtained in this study align so well with areas critical for integration of bodily information and areas previously implicated establishment of regulatory behaviors in children and adults.

“The implication of this work is that BMI of a mother relates to rapidly developing connections in her baby’s brain - even before that baby is born,” Dr. Thomason told us. “This can be helpful in terms of recommendations made to expectant mothers and can be beneficial for understanding underlying mechanisms (in this case specific neural connections) that may help to explain why children born to high BMI mothers sometimes show