Karyotyping of at risk fetuses by cordocentesis in advanced gestation.

Fetal blood obtained by cordocentesis was cultured to obtain rapid karyotypes of fetuses at risk during the late second trimester. Ninety nine fetal blood samples were studied for chromosomal abnormalities. The commonest indications for the procedure were abnormalities detected on ultrasonography (47.7%), and previous child with Down syndrome. Analysis of the 67 successful cultures showed four (5.9%) karyotypic abnormalities. The technique proved helpful in the obstetrical management of at risk fetuses.