简介：AbstractBackground:China’s two-child policy has led to a trend of aging in pregnancy which was associated with adverse outcomes. This study aimed to identify the clinically cutoff maternal age for adverse obstetric outcomes in China.Methods:This secondary analysis of a multicenter retrospective cohort study included data of childbearing women from 39 hospitals collected in urban China during 2011 to 2012. Logistic regression was used to assess the adjusted odds ratios (aOR) of adverse outcomes in different age groups in comparison to women aged 20 to 24 years. The adjustments included the location of the hospital, educational level, and residence status. Clinically cutoff age was defined as the age above which the aOR continuously become both statistically (P < 0.05) and clinically (aOR > 2) significant.Results:Overall, 108,059 women were recruited. In primiparae, clinically cutoff maternal ages for gestational diabetes (aOR: 2.136, 95% confidence interval [CI]: 1.856-2.458, P < 0.001), placenta previa (aOR: 2.400, 95% CI: 1.863-3.090, P < 0.001), cesarean section (aOR: 2.511, 95% CI: 2.341-2.694, P < 0.001), hypertensive disorder (aOR: 2.122, 95% CI: 1.753-2.569, P < 0.001), post-partum hemorrhage (aOR: 2.129, 95% CI: 1.334-3.397, P < 0.001), and low birth weight (aOR: 2.174, 95% CI: 1.615-2.927, P < 0.001) were 27, 31, 33, 37, 41, and 41 years, respectively. In multiparae, clinically cutoff ages for gestational diabetes (aOR: 2.977, 95%CI: 1.808-4.904, P < 0.001), hypertensive disorder (aOR: 2.555, 95% CI: 1.836-3.554, P < 0.001), cesarean section (aOR: 2.224, 95% CI: 1.952-2.534, P < 0.001), post-partum hemorrhage (aOR: 2.140, 95% CI: 1.472-3.110, P < 0.001), placenta previa (aOR: 2.272, 95% CI: 1.375-3.756, P < 0.001), macrosomia (aOR: 2.215, 95% CI: 1.552-3.161, P < 0.001), and neonatal asphyxia (aOR: 2.132, 95% CI: 1.461-3.110, P < 0.001) were 29, 31, 33, 35, 35, 41, and 41 years, respectively.Conclusions:Early cutoff ages for gestational diabetes and cesarean section highlight a reasonable childbearing age in urban China. The various optimized cutoff ages for different adverse pregnancy outcomes should be carefully considered in childbearing women.