Association between birth weight and massive haemorrhage in pregnancy with a low-lying placenta: a 9-year single-centre retrospective cohort study in Japan

A low-lying placenta is a well-known cause of a massive intrapartum haemorrhage. We aimed to evaluate whether neonatal birth weight deviation from the nationwide average could predict a massive haemorrhage during a delivery in the women with a low-lying placenta. This study included 40 women. The main outcomes were a massive haemorrhage and a neonatal birth weight deviation. We used a receiver operating characteristic curve analysis to determine the optimal birth weight deviation cut-off for predicting a massive haemorrhage. A multiple logistic regression model was used to identify the variables significantly associated with a massive haemorrhage. The best cut-off for predicting a massive haemorrhage was a birth weight deviation of +0.51 standard deviations (SDs) from the nationwide average. A birth weight deviation of >= +0.51 SDs was significantly associated with an increased massive haemorrhage risk. Impact statement What is already known on this subject? A low-lying placenta is a well-known cause of a massive intrapartum haemorrhage. Therefore, when managing pregnancies with a low-lying placenta, the possibility of severe perinatal bleeding should be considered, and it is desirable to determine reliable predictors of a haemorrhage. However, few studies have reported the predictive factors of a massive haemorrhage in patients with a low-lying placenta. What do the results of this study add? We demonstrated that a birth weight deviation from the nationwide average was significantly associated with a massive intrapartum haemorrhage in patients with a low-lying placenta. To our knowledge, this is the first study to clarify the association between a neonatal birth weight and a massive intrapartum haemorrhage incidence and to determine the optimal birth weight deviation cut-off for predicting a massive haemorrhage in patients with a low-lying placenta.