Pregnant people who consumed a high-quality balanced diet of whole grains, fruits, vegetables, and fatty acids had a lower risk of fetal growth restriction compared with those who consumed lower-quality diets, researchers found.

After adjusting for chronic hypertension and obesity, pregnant people who had a diet with a higher score on the Healthy Eating Index (HEI) were 67% less likely to have fetal growth restriction (estimated fetal weight below the 10th percentile) versus those who had diets with lower scores (adjusted relative risk [aRR] 0.33, 95% CI 0.13-0.68), reported Xiao Yu Wang, MD, of the Washington University School of Medicine in St. Louis.

A high-quality diet was also associated with a 54% decreased risk for hypertensive disorders of pregnancy (aRR 0.46, 95% CI 0.24-0.79), Wang said during a presentation at the Society for Maternal-Fetal Medicine virtual meeting.

Diet quality was not associated with large-for-gestational age, preterm birth, gestational diabetes, or unplanned cesarean delivery.

Only 17% of study participants had high diet quality scores, Wang said, noting that diet quality was associated with sociodemographic factors such as race, insurance status, and area deprivation index. He emphasized that there are “complex socioeconomic factors that affect nutritional quality on the individual and systemic level,” including access to and affordability of highly nutritional food options.

The HEI tool could be useful “to assess both personal and systemic dietary quality to improve maternal and fetal outcomes,” he said.

Wang’s group conducted a secondary analysis of a single-center prospective cohort study on preterm birth to evaluate the association between diet quality and fetal growth restriction. They analyzed people with singleton pregnancies who completed a dietary health questionnaire either during the third trimester or 3 months after delivery. Those who delivered at an outside hospital, became pregnant using in vitro fertilization, or had a pregnancy with fetal anomalies were excluded from the analysis.

The researchers categorized participants by their HEI score. Those with a score of 70 or greater were considered to have a high-quality diet, and those who scored below 70 had a low-quality diet. The primary outcome was fetal growth restriction, and secondary outcomes included hypertensive disorders, preterm birth, large-for-gestational age, gestational diabetes, and unplanned C-section delivery.

Overall, 762 people filled out the nutritional survey, with 83% reporting a lower-quality diet. Those with a lower score were more likely to be younger and African American, and have a higher starting BMI, lower rate of weight gain, and a higher rate of obesity. A low-quality diet was also associated with smoking, illicit drug use, nulliparity, a lower area deprivation index, and lower rates of private insurance.

Of participants with a higher-quality diet, 4.7% had fetal growth restriction compared with 13.9% of those with a lower-quality diet.

Higher dietary scores were associated with lower added sugar and saturated fat consumption, and a higher intake of whole fruits, greens and beans, whole grains, seafood and plant proteins, and fatty acids. Added sugars and fatty acids had the largest impact on the difference in dietary scores.

This study is limited by its reliance on self-reported dietary habits, and may be subject to recall bias and selection bias, Wang noted. In addition, as this was a third trimester study, it did not take into account dietary habits earlier in pregnancy.