Second trimester selective termination in a dizygotic twin pregnancy with discordancy for Down's syndrome: a case report.

A 34-year-old woman with a twin pregnancy underwent genetic amniocentesis in a local hospital at 18 weeks' gestation. Fetal chromosome analysis showed a boy without abnormal findings (46, XY) and another boy with trisomy 21 (47, XY, +21). Sonography showed a fetal nuchal translucency thickness for the normal twin of 4.4 mm, and of 8.0 mm for the affected twin. The affected twin was terminated by ultrasonographically guided intracardiac injection of 2.5 ml (5 mEq) potassium chloride solution at 21 weeks' gestation. Serial ultrasound scans and coagulopathy tests were unremarkable. Labor was induced at 39 weeks' gestation. A healthy 3,080 g male infant was born vaginally with Apgar scores of 8 and 9 at one and five minutes, respectively. At the time of writing (one month after delivery), the mother and baby continue to do well. To our knowledge, this is the second successful case in Taiwanese literature of selective birth in twins with discordancy for Down's syndrome.