Third trimester amniocentesis: a tool to aid choices concerning place of delivery and intrapartum management in haemophila carriers

Haemophilia A is an X linked recessive disorder with an annual incidence of 1 in 5,000 live male births. We report the case of a G2P1+0 (previous normal vaginal delivery), a known Haemophila A carrier. She presented at 10 weeks gestation when non invasive prenatal sex determination indicated she was carrying a male fetus, with a 1 in 2 chance of being affected. Her antenatal care was uneventful; her factor VIII levels having normalised at booking. She requested a home delivery. After counselling within the multidisciplinary team (including molecular genetics) she was offered and accepted late amniocentesis. Fortunately this was undertaken, without event, at 35+3 weeks gestation, and a week later culture growth allowed detection of a F8 c.6752t >C mutation, confirming Haemophilia A. Whilst mitigating against home delivery, given the mild nature of the disease within this kindred, we were still able to support delivery on a midwifery led unit. Third trimester amniocentesis is occasionally performed when structural abnormalities associated with aneuploidy are identified following ultrasound scan. However its use in this context has not been reported. Usual practice is to place location and intrapartum restrictions (to include no fetal blood sampling, no ventouse/rotational forceps) upon the management of women carrying a male fetus, accepting that 50% will be unaffected. This can mean an increase in deliveries undertaken at a tertiary unit and/or an increase in emergency caesarean sections. Results are encouraging. Late amniocentesis will continue to be offered and the outcomes will be audited.