The possible impact of the universal two-child policy on pregnancy outcomes

Purpose The implementation of the universal two-child policy contributes to adverse pregnancy outcomes, but how the policy change leads to adverse pregnancy outcomes is not well elaborated. In this study, we aimed to compare maternal characteristics and complications, accessed the change in the proportion of maternal characteristics and maternal complications, and evaluated the mediation of maternal characteristics on maternal complications.Methods Demographic and clinical data of three-level sample facilities were extracted from China's National Maternity Near Miss Obstetrics Surveillance System from Jan 1, 2012 to May 31, 2021. The associations between the universal two-child policy and maternal risk factors, the universal two-child policy and maternal complications, and maternal risk factors and maternal complications were evaluated using multivariate logistic regression analyses, with odds ratios (ORs) and 95% confidence intervals (CIs). Mediation analysis was used to estimate the potential mediation effects on the associations between the policy and maternal complications. Population-attributable fractions (PAF) were conducted to quantify the maternal complications burden attributable to the implementation of the universal two-child policy.Results In the context of the universal two-child policy, the incidence of maternal near miss, antepartum or intrapartum complication, and post-partum complication increased at municipal- and county-level sample facilities. After adjusting for covariables, there were significant associations between the universal two-child policy and maternal risk factors (P < 0.001), the universal two-child policy and an increased risk of maternal complications (P < 0.001), and maternal risk factors and maternal complications(P < 0.001). The effects of the universal two-child policy on maternal near miss and medical disease were significantly mediated by maternal risk factors with mediation proportions of 19.77% and 4.07% at the municipal-level sample facility, and mediation proportions for 2.72% at the county-level sample facility on medical disease. The universal two-child policy contributed 19.34%, 5.82%, 8.29%, and 46.19% in the incidence of the maternal near miss, antepartum or intrapartum complication, post-partum complication, and medical disease at municipal-level sample facility, respectively. The corresponding PAF% at county-level sample facility was 40.49% for maternal near miss, 32.39% for the antepartum or intrapartum complication, 61.44% for post-partum complication, and 77.72% for medical disease. For provincial-level sample facility, the incidence of maternal near miss, antepartum or intrapartum complications, and medical diseases decreased (P < 0.05) and no statistically significant difference occurred in the incidence of post-partum complications.Conclusions In the context of the universal two-child policy, the incidence of maternal near miss, antepartum or intrapartum complication, and post-partum complication increased at municipal- and county-level sample facility. Maternal risk factors may play a mediating role in the effect of policy change and maternal complications. Provincial hospitals have been able to improve the quality of perinatal health care and reduce adverse pregnancy outcomes by adjusting their obstetric service strategies in the context of the new birth policy.