Association of Parity with the Risks of Gestational Diabetes and Macrosomia: A Retrospective Cohort Study in Nanjing, China

Background: After implementing the two-child policy, more Chinese women who had a previous delivery had their second child. Nevertheless, the impacts of parity on Gestational Diabetes (GDM) and macrosomia have not been fully confirmed. Therefore, we aimed to analyse the characteristics of pregnancy by parity and evaluate the association of parity with risks of GDM/macrosomia in a Chinese population. Methods: A total of 193,410 pregnant women (including 148,293 primiparae and 45,117 multiparae) with complete information were included. Univariate and multivariate logistic regression analyses were used to examine the association between parity and risks of GDM/macrosomia. Results: With the gradual implementation of the two-child policy, the proportion of multiparae increased rapidly and then decreased slightly. Multiparae were more likely to be older and have higher intrapartum BMI, as compared to primiparae (P < 0.001). Univariate regression analyses suggested that parity could increase the risks of GDM and macrosomia; while after adjustment, the association between parity and GDM risk disappeared, and the effects of parity on macrosomia risk and birth weight of babies were also weakened. Further, stratified analysis showed that parity only increased the risk of GDM in women over 30 years, and the effects of parity on macrosomia risk and birth weight were more pronounced among women over 30 years compared to women under 30 years. Conclusion: Parity was not associated with GDM risk, but mildly associated with macrosomia risk. Particular attention should be paid to multiparae with advanced age to reduce the risks of GDM and macrosomia.