[Fetal atrioventricular interval measurement: technical aspects].

Atrioventricular (AV) interval measurement allows early diagnosis of isolated congenital heart block linked to maternal antibodies anti-Ro/SSA and/or anti-La/SSB. Simple and reliable ultrasound techniques have been developed to assess AV interval but most of them are imperfectly implemented by sonographers. In threatening conditions fetus should be regularly screened between 16 to 30 weeks. Increased AV interval defines the first degree AV block which should be treated by maternal-fetal corticosteroid to prevent complete heart block occurrence. The most recent ultrasound methods are based on pulsed Doppler rather than time-motion Doppler. We describe the most important technical aspects to improve the evaluation of the fetal AV interval.