The study, recently published in the American Journal of Clinical Nutrition and co-led by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, assessed diet quality in the same individuals from the beginning of pregnancy through one year postpartum. Few studies have analyzed diet quality in pregnancy and postpartum in the same participants.

Researchers used the USDA’s Healthy Eating Index (HEI), which is based on federal dietary guidelines, to develop a diet quality score for participants in the Pregnancy Eating Attributes Study (PEAS). Because diet quality during pregnancy and postpartum impacts short- and long-term health outcomes for parent and child, the team of perinatal nutritionists and epidemiologists aimed to identify risk factors for low diet quality to develop effective interventions.

The overall average HEI score for the study participants’ diets was ranked on a 0-100 scale at 61.6. On a traditional A-F scale, the grade would be barely passing, a D, although that score is 10% higher than the average HEI score of the overall U.S. adult population. The HEI score is based on the adequate consumption of nine foods — total fruit, whole fruit, total vegetables, greens and beans, whole grains, dairy, total protein, seafood, plant proteins, as well as fatty acids — and the consumption of four foods in moderation — refined grains, sodium, added sugars and saturated fats.

Among all the study participants, HEI scores were stable from early pregnancy through one year postpartum. But researchers noted differences in scores according to sociodemographic characteristics, weight status, lactation duration and tobacco smoking.

“You would think that pregnant women are highly motivated to eat better during pregnancy, precisely because they are pregnant. And that’s true in certain populations,” says senior author Anna Maria Siega-Riz, professor of nutrition, biostatistics and epidemiology and dean of the UMass Amherst School of Public Health and Health Sciences. “You saw higher-income women having a higher-quality diet, and lower-income women having a lower-quality diet.”

Siega-Riz notes that lower-income women may be working multiple jobs and either don’t have access to higher quality foods, can’t afford them or need more overall support from family, friends and healthcare providers. “You’re only capable of changing your diet if your income and your environment support it. And that, I think, is something that a lot of people forget,” she says.

Unmarried study participants and those participating in more than one federal assistance program recorded the lowest mean HEI scores. In addition, a higher body mass index (BMI) was associated with a lower-quality diet. The highest mean HEI scores were seen in participants with higher education and among those who reported never smoking.

“What women eat during pregnancy is mostly the same things they eat in the postpartum period, with the exception of a few foods,” she says. They sometimes return to caffeine and alcohol and resume eating more refined carbohydrates after giving birth.

The study participants’ diets were assessed at six points — in each trimester of pregnancy and two months, six months and one year postpartum. Overall, they scored high — A+ (100) — on eating enough whole fruits, total protein and greens and beans. They scored lowest — a failing grade — on eating adequate whole grains and fatty acids, and lower on dairy products. On the moderation side, they scored a lower grade on sodium intake and saturated fats than on added sugars and refined grains, though there were no high scores.

The message of the study? “Healthcare needs to change, to be more comprehensive. And right now, that’s not our model.,” Siega-Riz says. “Policymakers and prenatal care providers need to understand that even pregnant women need support and guidance to be able to change their dietary habits for the better.”

In a related PEAS study published in The Journal of Nutrition, Siega-Riz and team performed a genomic analysis of the gastrointestinal microbiome of participants during the second trimester of pregnancy after collecting fecal swabs.

“We wanted to look at the relationship between diet and what’s in the microbiome. And then also how the microbiome might be at interplay with what’s happening in utero that the fetus ends up being imprinted by,” she says.

The researchers found an association between a diet with higher saturated fat and added sugar and the composition and function of the microbiome during pregnancy. But they don’t know yet what that means. They will continue to examine both the parent’s and the child’s microbiome in ongoing and future research.

“Although the results provide an initial landscape of microbial factors that are associated with specific dietary components, such as dietary sugar, fat and dairy, the story is complicated and evolving, and we hope that these findings will be a foundation for future hypothesis-driven research and investigation,” the paper concludes.