Energy Density in Nulliparous Women Planning Pregnancy: Results from the ISIS Study

Abstract

BackgroundDietary energy density (ED) is a novel measure of diet quality that estimates the amount of energy per unit of food (kcal/g) consumed. Consuming an energy dense diet has been positively associated with obesity and risk of chronic disease.ObjectiveWe evaluated the association between ED and conception and pregnancy outcomes among participants of the ISIS study, a prospective cohort study of healthy, nulliparous women (n = 132) planning their first pregnancy (mean age± SD = 29.79 ± 3.21 and BMI = 24.30 ± 5.37 kg/m2).MethodsDietary data were collected prior to conception using a series of three unannounced, telephone 24‐hour dietary recalls, and ED was calculated from food (without beverages). Outcomes of interest included confirmed clinical pregnancy (CCP; hCG ≥ 20mIU/mL) and time to pregnancy (TTP; months).ResultsMean ED was 1.50 ± 0.36 kcal/g. The majority of participants (n=80; 61%) achieved CCP and the median TTP for those who conceived was 4.64 months with an interquartile range of 4.37 months. Preliminary data analyses, using Cox proportional hazards regression models, revealed that after controlling for race, physical activity and male partner's ED, higher dietary ED (continuous) among females was associated with longer TTP which approached statistical significance (HR= 0.48; 95% CI: 0.21–1.14, p=0.09). When ED was categorized into tertiles to consider non‐linear associations, 60%, 73%, and 50% of the participants in the tertiles (from lowest ED to highest) achieved CCP. In multivariable analyses with the middle group as the referent (ED=1.37–1.60), membership in the highest ED group (ED>1.60) was associated with longer TTP (HR= 0.41; 95% CI: 0.21–0.82, p=0.01). The estimated TTP for women in the lowest ED group (ED=0.85–1.36) was longer; but not statistically significant (HR=0.77; 95% CI: 0.42–1.42, p=0.40).ConclusionsResults of this study suggest that ED may be associated with TTP.Support or Funding InformationSupported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Numbers R01HD049762 and 3R01HD049762S1. Partial support provided by the CTSI (GCRC) at Penn State University NIH M01 107 32.