FIRST-TRIMESTER PRENATAL-DIAGNOSIS IN TWIN PREGNANCIES

Two twin pregnancies at risk for a sex-linked disorder are described. Both pregnancies were dichorionic. Transabdominal sampling was chosen for prenatal diagnosis. Molecular genetic techniques raised suspicion with regard to the accuracy of the samples in one case. Second-trimest er amniocentesis confirmed the error. Selective feticide of the affect ed fetus was performed. When first-trimester prenatal diagnosis is off ered in dichorionic twin pregnancies, confirmation through molecular g enetic testing can confirm that villi have been obtained from differen t fetuses. All parties must be aware that additional invasive diagnost ic procedures in the second trimester may be required in cases of doub t.