Adherence to Nordic dietary patterns and risk of first-trimester spontaneous abortion

PURPOSE: Evidence on the influence of modifiable risk factors on spontaneous abortion (SAB) is scarce. We investigated associations for adherence to national dietary guidelines and a healthy Nordic diet with first-trimester (≤ 12 weeks’ gestation) SAB in a Danish cohort of couples trying to conceive. METHODS: Participants completed a questionnaire on sociodemographics, lifestyle and reproductive history and a validated food frequency questionnaire (FFQ). We ascertained pregnancies from follow-up questionnaires and restricted analyses to 3,043 women who became pregnant. We assessed adherence to the Danish Dietary Guidelines Index (DDGI, range of 0–6, from low to high), covering intake of fruit, vegetables, fish, red and processed meat, whole grains, saturated fat and added sugar. The Healthy Nordic Food Index (HNFI, range 0–6) covered intake of fish, cabbage, rye bread, apples, pears, root vegetables and oatmeal. Pregnancy outcomes were identified through Danish medical registries or self-reported. We used Cox proportional hazards regression to compute hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for sociodemographics and lifestyle. RESULTS: Fifteen percent of participants had a first-trimester SAB. Compared with a DDGI score < 3, adjusted HRs (95% CIs) for scores 3 to < 4, 4 to < 5 and ≥ 5 were 0.85 (0.59–1.23), 0.78 (0.54–1.12) and 0.71 (0.44–1.13), respectively. Compared with an HNFI score < 2, adjusted HRs (95% CIs) for scores 2 to < 3, 3 to < 4, 4 to < 5 and ≥ 5 were 0.84 (0.62–1.15), 0.88 (0.66–1.19), 0.94 (0.69–1.28) and 0.69 (0.49–0.96), respectively. CONCLUSION: Greater pre-pregnancy adherence to Danish dietary guidelines or a healthy Nordic diet was associated with a lower rate of first-trimester SAB, although estimates were imprecise.