Relative risk of abnormal karyotype in fetuses found to have an atrioventricular septal defect (AVSD) on fetal echocardiography.

One hundred and twenty-five fetuses were identified as having an AVSD with normal venous connections, normal arterial connections and normal cardiac situs on fetal echocardiography. Fetal karyotype was known in 111 of these cases. The relative risk of fetal trisomy 21 at mid-trimester was 107 (95% CI 87-127) times the expected number of cases compared with risk from maternal age alone, and that for trisomy 21,18 or 13 was 95 (95% CI 79-109). This data may be useful in counselling pregnant women about risk of fetal karyotypic abnormality after a diagnosis of fetal AVSD.