The association between dietary patterns and risk of miscarriage: a systematic review and meta-analysis.

Importance: The evidence on the association between diet and miscarriage risk is scant and conflicting.

Objective: To summarize the evidence on the association between periconceptual diet and miscarriage risk in healthy women of reproductive age.

Data Sources: Electronic databases were searched from inception to August 2022 without restriction of regions, publication types, or languages.

Study Selection And Synthesis: Experimental or observational studies were considered for inclusion. The population was healthy women of reproductive age. Exposure was periconception diet. Study quality was assessed using the modified Newcastle-Ottawa Scale. Summary effect sizes (odds ratio [OR] with 95% confidence interval [CI]) were calculated for each food category.

Main Outcomes: Miscarriage rate (as defined by primary studies).

Results: We included 20 studies (11 cohort and 9 case-control), of which 6 presented data suitable for meta-analysis (2 cohort and 4 case-control, n = 13,183 women). Our primary analyses suggest a reduction in miscarriage odds with high intake of the following food groups: fruit (OR, 0.39; 95% CI, 0.33-0.46), vegetables (OR, 0.59; 95% CI, 0.46-0.76), fruit and vegetables (OR, 0.63; 95% CI, 0.50-0.81), seafood (OR, 0.81; 95% CI, 0.71-0.92), dairy products (OR, 0.63; 95% CI, 0.54-0.73), eggs (OR, 0.81; 95% CI, 0.72-0.90), and cereal (grains) (OR, 0.67; 95% CI, 0.52-0.87). The evidence was uncertain for meat, red meat, white meat, fat and oil, and sugar substitutes. We did not find evidence of an association between adherence to predefined dietary patterns and miscarriage risk. However, a whole diet containing healthy foods as perceived by the trialists, or with a high Dietary Antioxidant Index score (OR, 0.43; 95% CI, 0.20-0.91) may be associated with a reduction in miscarriage risk. In contrast, a diet rich in processed food was demonstrated to be associated with increased miscarriage risk (OR, 1.97; 95% CI, 1.36-3.34).

Conclusion And Relevance: A diet abundant in fruit, vegetables, seafood, dairy, eggs, and grain may be associated with lower miscarriage odds. Further interventional studies are required to accurately assess the effectiveness of periconception dietary modifications on miscarriage risk.

Prospero Registration: CRD42020218133.