Maternal and perinatal outcomes across China's one-child, two-child, and three-child policy periods: a retrospective cohort analysis of 43,439 deliveries

Background: China has sequentially implemented the one-child, two-child and three-child policies over the past 15 years, yet long-term effects of these fertility policy adjustments on maternal and perinatal health remain understudied. This study aimed to evaluate such impacts. Methods: A single-centre retrospective cohort analysis was conducted on 43,439 parturients delivering at a Guangxi hospital between 2011 and 2025. All participants were grouped into one-child (OCP), two-child (TCP) and universal three-child (UCP) policy cohorts. Multivariate logistic regression was applied to adjust for confounders and analyse the associations between fertility policies and the risks of caesarean section and postpartum haemorrhage (PPH). Results: Policy relaxation significantly increased maternal mean age (27.58 ± 4.85 to 31.37 ± 5.57 years), advanced maternal age (AMA) proportion (≥35 years, 9.3-30.5%), and in vitro fertilisation (IVF) utilisation (1.3-6.2%), while reducing the primipara ratio (66.3-39.9%) (all P < 0.001). Gestational diabetes mellitus (GDM) prevalence reached 26.7%, placental abruption (0.3-1.6%), caesarean section rate (29.6-39.9%), and emergency admissions (11.9-45.3%) all increased; hospital stay decreased (5.82-4.73 days) (all P < 0.001). Multivariate analysis showed lower caesarean section risk in TCP (adjusted odds ratio (aOR) = 0.91; 95% confidence interval (CI) = 0.86-0.95) but higher in UCP (aOR = 1.08; 95% CI = 1.02-1.15); an increase of one year in age raised caesarean risk by 8% (aOR = 1.08; 95% CI = 1.07-1.09). The TCP period exhibited the highest risk of PPH (aOR = 1.80; 95% CI = 1.55-2.10). Though caesarean delivery correlated with diminished PPH risk (aOR = 0.28; 95% CI = 0.24-0.33), this correlation stemmed from discrepant PPH diagnostic thresholds by delivery mode rather than a genuine protective benefit. Conclusions: Fertility policy relaxation coincided with altered maternal demographic profiles, elevated high-risk pregnancy and obstetric complication burdens, and greater emergency care demand. Such correlations highlight an urgent need for targeted optimisation of maternal healthcare delivery systems.