Why is post-partum haemorrhage more common in women with congenital heart disease?

To identify the factors associated with an increased post-partum blood loss in women with congenital heart disease (CHD).

The study was a retrospective cohort study, which included 366 nulliparous women with CHD and a singleton pregnancy cared for in a single tertiary centre (Chelsea and Westminster Hospital) between 1994 and 2014. The women were classified into one of 12 different functional groups and univariate and multivariate regression analysis were used to identify factors associated with increased blood loss at delivery.

The average volume of blood loss in women with CHD was twice that expected. Univariate analysis showed that White European women had the lowest blood loss. Women who had been on anticoagulants, had a forceps delivery, emergency Caesarean section or general anaesthesia lost more blood than those having a spontaneous vaginal birth under regional analgesia. Higher CARPREG scores were associated strongly with increased blood loss. Women with a Fontan circulation had the highest blood loss and the difference remained significant after correcting for other significant variables.

Women with CHD are at increased risk of PPH. We have identified several potentially modifiable risk factors that may be targeted to reduce this risk. In addition, women with a Fontan circulation were most prone to PPH, independent of other risk factors, suggesting the existence of lesion-specific abnormalities and the need for extra vigilance in this group of women at the time of birth.