A decrease in diet quality occurs during pregnancy in overweight and obese women which is maintained post-partum.

Background: Ensuring adequate dietary intake during pregnancy has important implications for optimising maternal and fetal health. It is not known whether diet quality is altered over pregnancy and the post-partum period.

Objective: The aim of this study was to perform a comprehensive assessment of diet quality in overweight and obese women during pregnancy and early post-partum.

Design: In a prospective cohort study, n=301 overweight or obese pregnant women completed a food frequency questionnaire at study entry (10-20 weeks gestation), 28 weeks gestation, 36 weeks gestation and 4 months post-partum for assessment of macronutrient and micronutrient intake and diet quality by the Healthy Eating Index (HEI).

Results: Energy, macronutrient and dietary sources of micronutrients did not alter across pregnancy or post-partum. The HEI was of below average quality in 31.0% of women at baseline. This decreased from week 28 (P<0.001) and was maintained at a lower level post-partum such that HEI levels were lower compared with study entry (53.3±12.7 versus 56.7±10.1, P<0.001). The HEI decrease occurred in association with decreases in the milk, meat and unsaturated oil components, and increases in the proportion of energy from solid fats, alcohol and added sugars (P<0.001), and was independently predicted by the socioeconomic index for areas score (β=-0.011, s.e.=0.011, P=0.031).

Conclusion: We report for the first time that dietary quality decreases across pregnancy and is maintained at this reduced level in the early post-partum period in overweight and obese women. Dietary interventions aimed at improving diet quality should be targeted to early pregnancy and post-partum.