Early ultrasonic diagnosis of conjoined twins

Conjoined twins is a rare congenital malformation occurring in 1:30,000-1:100,000 live births. Its early prenatal detection was extremely rare prior to the introduction of obstetric ultrasonography. We report 3 cases of early ultrasound diagnosis of conjoined twins at 9, 15 and 19 weeks of pregnancy, respectively. The diagnosis at 9 weeks of gestation was made via the transvaginal approach, and to the best of our knowledge is the earliest diagnosis reported in the English literature. In all 3 cases the fetuses were of the thoraco-omphalopagus type and had a shared heart. Pregnancy was discontinued in all 3 cases using methods appropriate for the first and second trimesters of pregnancy.