Association Between Maternal Copper/Zinc Intake and the Risk of Preterm Birth

Background: The relationship between maternal copper and zinc intake and the risk of preterm birth is unclear Objectives: This study was designed to investigate the effects of daily copper and zinc intake before and during pregnancy on the risk of preterm birth and to assess whether there is an interaction between copper and zinc intake and the risk of preterm birth Methods: A nested case - control study was conducted in Lanzhou, involving 880 cases and 8017 controls. Eligible participants were interviewed about their diet and characteristics during pregnancy. Unconditional logistic regression was used to determine the association between dietary copper and zinc intake and the risk of preterm birth, including its clinical subtypes. A multivariate adjusted restricted cubic spline (RCS) model was used to investigate the nonlinear relationship between dietary copper and zinc intake and the risk of preterm birth. Results: The study revealed that compared to pregnant women with the highest dietary copper intake before and during pregnancy, those with copper intake in the lower three quartiles (quartiles 1, 2, and 3) had increased risks of preterm birth, with adjusted odds ratios (ORs) of 1.05 (0.96 - 1.14), 1.05 (0.93 - 1.18), and 1.04 (0.82 - 1.32), respectively. The trend test yielded significant results (P = 0.013), particularly in late pregnancy, indicating an association between lower copper intake and increased risks of preterm and spontaneous preterm birth. Maternal dietary zinc intake during pregnancy was positively associated with the risk of preterm birth. The adjusted ORs for quartile 2 compared to quartile 4 were 1.29 (1.09 - 1.52), 1.55 (1.13 - 2.12), and 1.20 (1.00 - 1.46) throughout pregnancy, indicating significantly increased risks in the mid to late stages of pregnancy. No significant association was found between zinc intake and medically induced preterm birth. Zinc intake below the nutritional reference value in late pregnancy was significantly associated with an increased risk of preterm birth (P < 0.05). A nonlinear relationship was observed between copper/zinc intake and the risk of preterm birth (P Nonlinear < 0.05). A synergistic effect of low copper and zinc intake on the risk of preterm birth was found (OR: 2.23, 95% CI: 1.64 - 3.04, P < 0.001). Conclusions: Efforts to promote adequate copper and zinc intake before and during pregnancy need to be intensified to reduce the incidence of preterm birth.