The optimal childbearing age and birth spacing in china: a multicenter retrospective cohort study.

Background: We aimed to comprehensively analyze the impact of both maternal age and birth spacing on adverse maternal and neonatal outcomes.

Methods: A total of 151,301 pregnancies in China from January 1, 2010, to December 31, 2021 were included, and 8,222 subjects matched their primary and second pregnancy information. Join point regression was used to analyze the temporal trends of adverse outcomes with maternal age and birth spacing.

Results: The mean maternal age at delivery rose from 27.1 years to 28.5 between 2010 and 2021, and the average annual percentage change in advanced maternal age (≥ 35 years) was 1.2%. The optimal childbearing age (with the fewest adverse outcomes) appears to be 27 years. Compared with women aged 27 years, both those aged < 27 years and those aged > 27 years exhibited a significantly higher risk of anemia, low birth weight (LBW), preeclampsia, and preterm birth. In addition, we found that the optimal primiparous childbearing age was 26 years old and birth spacing was 3 years, < 3 years increased the risk of FGR, oligohydramnios, placenta previa, preeclampsia, LBW, preterm birth and premature rupture of membranes (PROM). While birth spacing > 3 years significantly increased the risks of anemia, gestational diabetes mellitus (GDM), placenta previa, preeclampsia, thyroid dysfunction (TD), preterm birth and PROM. The subgroup analysis revealed that the common adverse outcomes increased with longer birth spacing in pregnant women < 26 years, while these adverse outcomes showed lowest prevalence rates at 3-year birth spacing in pregnant women > 26 years.

Conclusions: The age of childbearing continues to be delayed, and we are in favor of having children at relatively optimal ages and spacing.