Postpartum haemorrhage in women with mild factor XI deficiency.

INTRODUCTION: With the advent of direct-to-consumer genetic testing, mild factor XI deficiency is increasingly recognized. There are limited data regarding the risk of postpartum haemorrhage (PPH) among women with mild FXI deficiency following obstetrical delivery.

AIM: To assess the risk of PPH among women with mild FXI deficiency undergoing vaginal or caesarean delivery.

METHODS: We conducted a retrospective, case-control study, in women with FXI levels between 20% and 70% of normal. For a control population, delivery outcomes were analysed in 200 women (between 2016 and 2018) without known bleeding disorders.

RESULTS: There was no PPH among 45 vaginal deliveries in women with mild FXI deficiency compared with one PPH among 125 vaginal deliveries in the control cohort. The rate of PPH was significantly higher among the 26 caesarean deliveries in women with mild FXI deficiency relative to 75 control caesarean deliveries (odds ratio 2.73, 95% CI 1.02-7.26, P = .04). Prior history of haemorrhage was a strong predictor of PPH following caesarean delivery. All women who developed PPH following caesarean delivery had either a history of haemorrhage or independent risk factor for PPH.

CONCLUSION: Due to the low rates of postpartum haemorrhage following vaginal delivery, routine prophylaxis to prevent postpartum haemorrhage in the setting of mild FXI deficiency does not appear warranted, especially in the absence of a bleeding history. Mild FXI deficiency is associated with an increased risk of PPH following caesarean delivery.