Association between maternal dietary diversity during pregnancy and birth outcomes: evidence from a systematic review and meta-analysis.

Background: Maternal nutrition is a key factor influencing birth and offspring health outcomes in later life. Dietary diversity (DD) is a proxy for the macro/micronutrient adequacy of an individual's diet. There is inadequate comprehensive evidence regarding maternal nutrition during pregnancy, measured through DD and birth outcomes. This study aimed to provide extensive evidence on maternal DD during pregnancy and birth outcomes.

Methods: A comprehensive search was performed using PubMed, HINARI, and Google Scholar databases up to January 17, 2024. Studies conducted among pregnant mothers and measuring maternal DD with an evaluation of birth outcomes (low birth weight, small for gestational age, preterm birth), in the global context without design restriction were included. The Newcastle Ottawa Scale and the Cochrane Risk of Bias tool were used to assess the risk of bias. The results are summarized in a table, and odds ratios were pooled where possible. Between-study heterogeneity was evaluated using I² statistics. Potential publication bias was assessed using a funnel plot and Egger's regression test. To explore the robustness, a leave-one-out sensitivity analysis was conducted.

Results: Thirty-three studies were used to synthesize narrative evidence (low birth weight: 31, preterm birth: 9, and small for gestational age: 4). In contrast, 24 records for low birth weight, eight for preterm birth, and four for small for gestational age were used to pool the results quantitatively. Of the 31 studies, 17 reported a positive association between maternal DD and infant birth weight, 13 studies reported a neutral association (not statistically significant), and one study reported a negative association. Overall, inadequate DD increased the risk of low birth weight OR = 1.71, 95% CI; (1.24-2.18), with I² of 68.7%. No significant association was observed between maternal DD and preterm birth. Inadequate DD was significantly associated with small for gestational age (OR = 1.32, 95% CI; 1.15-1.49, and I² = 0.0%).

Conclusion: Inadequate maternal DD is associated with an increased risk of low birth weight and small for gestational age but not preterm birth, underscoring the importance of promoting adequate DD during pregnancy. To address these issues, it is essential to implement and expand nutritional programs targeted at pregnant women, especially in low-resource settings, to ensure they receive diverse and adequate diets. Further research is needed to address the current limitations and to explore the long-term implications of maternal nutrition on child health. The study was prospectively registered on PROSPERO (registration number CRD42024513197). No funding was received for this study.