Trends in maternal age and the relationship between advanced age and adverse pregnancy outcomes: a population-based register study in Wuhan, China, 2010-2017.

Objectives: The aims of this study were to assess trends in maternal age in central China and to examine the relationship between maternal age and adverse pregnancy outcomes.
Study Design: This was a retrospective and observational study.
Methods: Data were analysed from the Wuhan Maternal and Child Health Management Information System, which included all pregnant women who were at 24-42 weeks' gestation, with singleton pregnancies and who lived in Wuhan between 2010 and 2017. Joinpoint regression was used to analyse the trends in mean maternal age and the proportion of women with advanced maternal age. Adverse pregnancy outcomes, including pregnancy-induced hypertension (PIH) disorder, gestational diabetes mellitus (GDM), caesarean delivery, postpartum haemorrhage, preterm birth, small for gestational age, large for gestational age (LGA) and 5-min Apgar score <7 among women aged <20, 20-24, 30-35 and ≥40 years were compared with women aged 25-29 years using multivariate binary logistic regression analysis and stratified analysis.
Results: Among the 583,571 women included in this study, 1.2% were aged <20 years, 20.8% were aged 20-24 years, 47.9% were aged 25-29 years, 22.0% were aged 30-34 years, 6.9% were aged 35-39 years and 1.2% were aged ≥40 years. Between 2010 and 2017, the mean maternal age increased from 27.1 years to 29.7 years, and the proportion of women aged ≥35 years increased from 4.3% to 13.9%. Relative to women aged 25-29 years, women aged ≥30 years carried higher risks of PIH, GDM, caesarean delivery, preterm birth, LGA and 5-min Apgar score <7. Relative to older multiparous women, older nulliparous women were more likely to experience caesarean delivery, preterm birth and 5-min Apgar score <7.
Conclusions: The average maternal age and the proportion of advanced maternal age showed increasing trends between 2010 and 2017, which may be related to the relaxation of the one-child policy in China. Older maternal age (≥30 years) is independently associated with various adverse pregnancy outcomes. The risks of adverse pregnancy outcomes may occur earlier than the commonly used definition of advanced maternal age (≥35 years) and may also differ by parity. Ensuring age- and parity-specific clinical counselling, antenatal surveillance and health interventions may significantly improve pregnancy outcomes in older mothers.
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