The objective of this study was to evaluate the value of clinical and ultrasound risk factors in predicting severe postpartum haemorrhage (PPH) (≥1.5 L) in pregnancies undergoing caesarean section for placenta praevia. This cohort consists of all cases of placenta praevia undergoing caesarean delivery over a period of 5 years in a service unit. Patients and their delivery data were retrieved from an obstetric database. Ultrasound features were prospectively recorded before caesarean section. The incidence of caesarean section for placenta praevia was 0.98% (n = 215). Of these, 12.1% (n = 26) had severe PPH. A logistic regression model showed that major praevia, antepartum haemorrhage before delivery and anterior placenta remained significant factors associated with severe PPH. The sensitivity/specificity and positive/negative predictive value of the model are 96.2%, 59.8%, 24.8% and 99.1%, respectively. Our model had high sensitivity and negative predictive value for severe PPH during caesarean section for placenta praevia.Impact statementWhat is already known on this subject? Placenta praevia is known to be one of the leading causes of severe PPH. Many risk factors have been associated with severe bleeding during caesarean section for placenta praevia. However, the importance of individual factors in predicting pregnancy outcome remains controversial.What the results of this study add? Our model includes only three simple parameters, namely the presence of significant antepartum haemorrhage (APH) from the history, and anterior or posterior placenta and major or minor praevia from ultrasound findings, but could predict up to 96.2% of all severe PPH. More importantly, the absence of APH, a posterior minor praevia, was associated with a negative predictive value of 99.1% of severe PPH, implying that such cases could be treated as 'normal' low risk caesarean sections.What the implications are of these findings for clinical practice and/or further research? This simple model would allow differential pre-operative counselling of patients on risks and complications, planning and preparation of operation, allocation of staff as well as in contingency measures to be taken during operation. The establishment of a differential protocol for placenta praevia based on these simple risks factors and a prospective trial of such a protocol is suggested.
Keywords: Placenta praevia; caesarean section; low-lying placenta; postpartum haemorrhage; risk factor.