BackgroundTo determine the effects of maternal age at first cesarean on maternal complications and adverse outcomes of pregnancy with the second cesarean.MethodsThis was a multicenter, historical, cross-sectional cohort study involving singleton pregnancies >= 28 gestational weeks, with a history of 1 cesarean delivery, and who underwent a second cesarean between January and December 2017 at 11 public tertiary hospitals in 7 provinces of China. We analyzed the effects of maternal age at first cesarean on adverse outcomes of pregnancy in the second cesarean using multivariate logistic regression analysis.ResultsThe study consisted of 10,206 singleton pregnancies. Women were at first cesarean between 18 and 24, 25-29, 30-34, and >= 35years of age; and numbered 2711, 5524, 1751, and 220 cases, respectively. Maternal age between 18 and 24years at first cesarean increased the risk of placenta accreta spectrum (aOR, 1.499; 95% CI, 1.12-2.01), placenta previa (aOR, 1.349; 95% CI, 1.07-1.70), intrahepatic cholestasis of pregnancy (aOR, 1.947; 95% CI, 1.24-3.07), postpartum hemorrhage (aOR, 1.505; 95% CI, 1.05-2.16), and blood transfusion (aOR, 1.517; 95% CI, 1.21-1.91) in the second cesarean compared with the reference group (aged 25-29years). In addition, maternal age >= 35years at first cesarean was a risk factor for premature rupture of membranes (aOR, 1.556; 95% CI, 1.08-2.24), placental abruption (aOR, 6.464, 95% CI, 1.33-31.51), uterine rupture (aOR, 7.952; 95% CI, 1.43-44.10), puerperal infection (aOR, 6.864; 95% CI, 1.95-24.22), neonatal mild asphyxia (aOR, 4.339; 95% CI, 1.53-12.32), severe asphyxia (aOR, 18.439; 95% CI, 1.54-220.95), and admission to a neonatal intensive care unit (aOR, 2.825; 95% CI, 1.54-5.17) compared with the reference group (aged 25-29years).ConclusionsMaternal age between 18 and 24years or advanced maternal age at first cesarean was an independent risk factor for adverse maternal outcomes with the second cesarean. Advanced maternal age at the first cesarean specifically increased adverse neonatal outcomes with the second. Therefore, decisions as to whether to perform a first cesarean at a young or advanced maternal age must be critically evaluated.