The incidence, associated factors and adverse maternal and perinatal outcomes of uterine rupture among vaginal births after caesarean section: An observational study from the National Maternal Near-Miss Surveillance System in China

Abstract Background The most serious problem during vaginal birth after caesarean section (VBAC) is the risk of uterine rupture but there is controversy regarding important related factors. With the relaxation of birth policy in China, the maternal and perinatal outcomes after uterine rupture during VBAC are a societal concern. The lack of any large-scale study of uterine rupture during VBAC in China underscores the need for more research evidence. Methods We studied singleton pregnant women with VBAC from 2012 to 2019 registered in China’s National Maternal Near-Miss Surveillance System (NMNMSS). First, we calculated the incidence of uterine rupture during VBAC. Second, using a logistic regression model with weighting for the sampling distribution of the population and clustering of births within hospitals, we examined the association of sociodemographic and obstetric characteristics and maternal diseases with uterine rupture during VBAC. With multivariable logistic regression, adjusted odds ratio were estimated using two models. Finally, we compared the risk of adverse maternal and perinatal outcomes in women with and without uterine rupture during VBAC. Results This study included 155774 singleton pregnant women with VBAC, and the incidence of uterine rupture was 0.23%. Characteristics associated with the increased risk of uterine rupture during VBAC included two (aOR = 1.70; 95% CI: 1.06–2.73) and three or more (aOR = 2.59; 95% CI: 0.54–12.44) previous caesarean sections, delivery at 42 weeks or later (aOR = 2.62; 95% CI: 1.58–4.35), and foetal birthweight greater than 4000 g (aOR = 1.93; 95% CI: 1.30–2.87). Compared with those without these conditions, the risk of uterine rupture during VBAC among women with amniotic fluid embolism, severe anaemia, placenta accreta spectrum, placental abruption, preeclampsia or eclampsia, and mild anaemia was 25.7-fold, 15.89-fold, 4.17-fold, 3.96-fold, and 2.49-fold higher, respectively. The incidence of adverse maternal outcomes during VBAC was higher in women with uterine rupture than in women without. Conclusion The incidence of uterine rupture during VBAC is comparable between China and some developed countries. In the clinical medical practice of obstetrics, it is necessary to be vigilant to factors associated with uterine rupture during VBAC and identify uterine rupture as soon as possible to improve maternal and perinatal outcomes.