Prenatal karyotyping of twins by ultrasonically guided amniocentesis

Twins were diagnosed with ultrasound in two women who had been referred because of a higher than normal risk of having malformed children. Amniocentesis was carried out under the guidance of ultrasound and amniotic fluid from both fetuses was removed for diagnostic procedures. Injection of Congo red proved that the amniocentesis needle was not re-entering the same amniotic cavity at repeated puncture. In both mothers the fetuses were found to be of different sexes. Mixture of maternal cells was excluded by means of quinacrine staining, allowing evaluation of chromosome markers.