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

Retrospective UK multicentre study of the pregnancy outcomes of women with a Fontan repair

“…Previously, we have shown that women with a Fontan circulation have a greater risk of PPH than women with other cardiac lesions 22. In 13% of deliveries (7 of 54) women had a major obstetric haemorrhage (blood loss >2000 mL).…”

The management of the third stage of labour in women with heart disease

“…As a result, only one patient was in NYHA class >1. Work from our group has shown women with a Fontan repair and pulmonary hypertension have a greater degree of haemorrhage at delivery; therefore, having more women with these lesions in our study may have influenced our results 4. Given that the population of women with HD is heterogeneous and while the oxytocin regimen was well tolerated by all in the study, it is possible that other women would experience an adverse response to higher doses.…”

“…PPH rates are increasing not only due to better measurement of blood loss but also due to the combination of obstetric variables 3. For many years, women with HD have been shown to beat greater risk of PPH, but only recently have studies begun to examine the reasons for this 4. We have shown that uterine atony is the main factor responsible for PPH in women with HD,5 as with the normal population, but that anticoagulant usage and mode of delivery were particularly important.…”

“…In our centre, we have used a ‘low-dose’ oxytocin infusion (10 U of oxytocin diluted in 500 mL of normal saline given at a rate of 36 mL/hour for 4 hours (12 mU/min)) in women with HD over the last 20 years and have observed high rates of PPH in such women at 23% 4. The aim of this study was to examine the hypotheses that giving as low (over 10 min) bolus of 2 IU of oxytocin, in addition to the usual ‘low-dose’ oxytocin infusion for the management of third stage of labour does not increase adverse cardiovascular events (arrhythmia, chest pain, documented ST segment changes) and reduces blood loss at delivery.…”

Pregnancy in women with congenital heart disease

“…A retrospective UK study (366 pregnancies) reported that postpartum haemorrhage occurred in 25% of women with congenital heart disease. Women with a Fontan circulation or taking anticoagulants were at greatest risk 10. An American study of 50 women with aortic coarctation showed that up to 30% developed pregnancy induced hypertension or pre-eclampsia 11…”