The association between periconceptional diet quality and adverse pregnancy outcomes

Background: Diet quality during the periconceptional period can have consequences on pregnancy outcomes with potential life course implications for the pregnant person and the offspring. The Healthy Eating Index (total score) has been related to risk of adverse pregnancy outcomes. Little research has been done, however, evaluating associations of each component of the score with adverse pregnancy outcomes. Further, potential effect modification of these associations by pre-pregnancy body mass index (BMI) or race/ethnicity has not been examined. Methods: The study was conducted using information obtained as part of a prospective cohort study – the Nulliparous Pregnancy Outcome Study: Monitoring Mothers to be (NuMoM2b). The NuMoM2b was conducted among participants (n = 6,721) recruited from eight medical centers across the U.S. Exposures were the 2010 Healthy Eating Index component (Adequacy scores: total vegetables, greens and beans, total fruit, whole fruit, whole grains, dairy, total protein foods, seafood and plant protein, fatty acid ratio (poly- and monosaturated fatty acids over saturated fatty acids). Moderation scores: refined grains, sodium, and empty calories (SOFAAS: solid fats, alcohol, and added sugars)) and total scores in the periconceptional period. Adequacy components scores have a higher score with higher intake, while moderation components have a higher score with lower intake. Outcomes were adverse pregnancy outcomes, including hypertensive disorders of pregnancy, gestational diabetes mellitus (GDM), and preterm birth (PTB). Hypertensive disorders of pregnancy were defined according to the American College of Obstetricians and Gynecologists. GDM was defined using White’s classification. PTB was defined as birth before 37 completed weeks of gestation. Multivariable Poisson regression models were used to estimate adjusted relative risks and corresponding 95% confidence intervals (CIs). The adjustment variables included maternal age, maternal education, maternal race and ethnicity, pre-pregnancy BMI, tobacco use, total energy intake (kcals), and each component score that was not the exposure. Effect modification by race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, Asian, and Other) and pre-pregnancy BMI (normal, obese, overweight) were assessed using models with interaction terms and stratified multivariable Poisson regression models, as described above. Results: Participant were on average 27.7 years old and 66.2% non-Hispanic White. With each increase in HEI score quartile, participants were more educated (82.3% college educated or more) and had a higher total household income (66.4% with 75k+). In fully adjusted models, the risk of GDM was higher with each unit increase of total protein component score (aRR:1.29, 95% CI: 1.08-1.53) and each unit increase of the dairy component score (aRR: 1.06, 95% CI: 1.01-1.13). The risk of GDM was lower with each unit increase of SOFAAS component score (aRR: 0.960, 95% CI: 0.923-0.998). We also found a higher refined grains component score was associated with a lower risk of gestational hypertension (aRR: 0.95, 95% CI: 0.902-0.997). The risk of PTB was lower with each unit increase of total vegetable (aRR: 0.90, 95% CI: 0.814-0.996) and greens and beans (aRR: 0.89, 95% CI: 0.84-0.95) component scores. We did not find any significant association between chronic hypertension or preeclampsia-eclampsia and the HEI scores. Among non-Hispanic White participants, we found a 10% lower risk of gestational hypertension with each unit increase of seafood and plant protein score (aRR: 0.90, 95% CI: 0.82-0.99). Among Asian participants, we found the risk of gestational hypertension was higher with each unit increase of whole fruit (aRR: 4.31, 95% CI: 1.25-14.89) and fatty acid ratio (aRR: 1.89, 95% CI: 1.29-2.79) scores. Among participants of Other race/ethnicity, the risk of GDM was higher with each unit increase of greens and beans component score (aRR: 3.76, 95% CI: 1.42-9.93). We did not find similar associations among any of the other race/ethnicity strata (confidence intervals crossing one). The risk of gestational hypertension was higher by 23% with each unit increase of whole fruits among participants with obesity (aRR:1.23, 95% CI: 1.03-1.46) but not among normal or participants with overweight (aRR: 1.03, 95% CI: 0.90-1.19 and aRR: 0.99, 95% CI: 0.83-1.18, respectively, p-value for interaction < 0.05). Lastly, there was a potential trending, but not statistically significant, association of PTB with total protein component score among participants with obesity (aRR: 1.23, 95% CI: 0.96-1.58). Conclusions: We found that higher total protein and dairy scores were associated with higher risk of GDM, while a higher SOFAAS score was associated with a lower risk of GDM. We also found a higher refined grains score was associated with a lower risk of gestational hypertension, and higher total vegetable and greens and beans scores were associated with a lower risk of PTB. Race/ethnicity and pre-pregnancy BMI modified seafood and plant protein-gestational hypertension and whole fruit-gestational hypertension associations, respectively.