Maternal dietary vitamin A and polyunsaturated fatty acids intake and risk of preterm birth: a nested case-control study

Background The impact of maternal dietary intake of vitamin A and polyunsaturated fatty acids (PUFAs) on preterm birth (PTB) risk remains uncertain. This study aims to investigate the effects of preconception and pregnancy dietary intake of these nutrients on PTB risk and to examine potential interactions between vitamin A and PUFAs. Methods The study subjects were pregnant women who registered at the Perinatal Medicine Center of Gansu Provincial Maternity and Child-care Hospital between March 2018 and March 2019 and whose birth outcomes could be followed up. Following ethics approval and consent, one-on-one pregnancy diet surveys established a total dietary intake database for statistical analysis. PTB was used as the outcome variable, and intake levels of different substances during pregnancy were used as independent variables. Logistic regression models were employed to calculate odds ratios (OR) and their 95% confidence intervals (CI) to analyze the impact of various substance intake levels on PTB. Results A total of 8,897 pregnant women were enrolled in this study, comprising 880 cases and 8,017 controls. Multivariate logistic regression analysis indicated that when dietary intake of vitamin A and PUFAs levels w as too low in the third trimester, the risk of PTB would be significantly increased. The specific results were (OR = 1.440, 95% CI [1.221–1.697]) and (OR = 1.319, 95% CI [1.113–1.563]), respectively. Similar conclusions were drawn in the gestational weeks subgroup. In addition, a U-shaped association was found in the third trimester of pregnancy between the intake level of dietary PUFAs and the risk of PTB, meaning that both excessive and insufficient intake increase the risk of PTB. Interaction analysis revealed that dietary vitamin A and PUFAs intake had a multiplicative interaction effect on the risk of PTB during preconception and pregnancy. Conclusion An increased risk of PTB is associated with low intake of vitamin A and PUFAs both pre-conception and during pregnancy. Furthermore, a nonlinear relationship between intake levels and PTB risk was observed ( P < 0.05). To reduce the risk of PTB, it is recommended that women maintain adequate dietary intake of vitamin A and PUFAs both preconception and throughout pregnancy.