Improvement in Maternal Diet Quality Across Pregnancy Is Associated With Lower Gestational Weight Gain in Women With Obesity From the Illinois Kids Development Study

Background: It is unclear how dietary patterns are associated with gestational weight gain (GWG) because prior studies focused on individual foods and did not consider diet at multiple timepoints. Objective: This study aimed to evaluate associations between changes in diet quality across pregnancy with GWG. Design: This secondary data analysis included women from the Illinois Kids Development Study, a longitudinal prospective cohort. Participants/Setting: Participants were 380 women recruited from 2013 through 2018 from obstetric clinics in Champaign-Urbana, IL, who were followed through delivery. Main Outcome Measures: At median 13 and 35 weeks of gestation, participants completed 3-month semi-quantitative food frequency questionnaires to calculate the Healthy Eating Index 2015 and Alternative Healthy Eating Index 2010, excluding alcohol. Change in diet quality was calculated by subtracting diet quality scores at 13 weeks from those at 35 weeks. Gestational age- and prepregnancy body mass index (BMI)–specific GWG z scores were calculated using weight before pregnancy and at a median 38 weeks of gestation along with an international reference chart. Using prepregnancy BMI (calculated as kg / m²), women were classified as having underweight or healthy weight (BMI <25), overweight (BMI 25-29.9), or obesity (BMI ≥30). Statistical Analyses Performed: Covariate-adjusted linear regression models accounting for total energy intake evaluated associations of improvement in Healthy Eating Index 2015 or Alternative Healthy Eating Index 2010 across pregnancy with GWG z scores. Differences by prepregnancy BMI were also explored. Results: In women with obesity (who drove overall associations), each 10-point improvement in Healthy Eating Index 2015 across pregnancy was associated with –0.55 (95% CI, –0.82 to –0.27) lower GWG z scores due to decreased refined grains intake and increased seafood and plant proteins intake. A similar relationship was observed when considering the Alternative Healthy Eating Index 2010 (β = –0.48; 95% CI, –0.81 to –0.15) due to higher nuts and legumes intake. Conclusions: Accounting for energy intake, diet quality improvement across pregnancy was associated with lower GWG z scores, particularly in women with obesity. Future studies may consider the implications of these findings for maternal and child health.