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

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.

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.

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.

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.