First trimester prenatal diagnosis by transcervical chorionic villus sampling using curved biopsy forceps: lessons of the first 30 continuing pregnancies.

Transcervical chorionic villus sampling was performed on 30 pregnancies who were at risk for chromosomal abnormalities between 9 and 12 weeks of gestation to determine whether the developing fetus had a chromosomal disorder. Curved biopsy forceps were passed transcervically into the chorion frondosum under continuous real-time ultrasound guidance, and chorionic villi were biopsied. Chorion yield was assessed semiquantitatively. An adequate villus sample was obtained in all cases, giving a success rate of 100 per cent. The average weight of the villi was 18.8 mg with a lower limit of 10 mg which proved sufficient for diagnostic purposes. The villi were processed for chromosomal analyses by cultured preparations. A diagnostic result was achieved in 28 of cases (93.3%) within 2 weeks. No major maternal complications were encountered. The fetal loss rate was 3.3 per cent. No fetal anomalies were found in the study group. It is concluded that transcervical chorionic villus sampling appears to be a relatively safe and reliable procedure, but the risk of miscarriage can only be accurately assessed after further investigation. In contrast to amniocentesis, the procedure is performed early in pregnancy and results of the genetic test are available during the first trimester. We believe that transcervical chorionic villus sampling offers an alternative to amniocentesis in the detection of genetic disorders.

Multiplex PCR to detect the dystrophin gene deletion in Thai patients.

We have demonstrated the usefulness of the multiplex PCR to directly detect the dystrophin gene mutation. Prenatal diagnosis and confirmation of clinical diagnosis of DMD/BMD via non invasive technique are now possible. Nine DMD and one BMD patients were tested. Five DMD patients demonstrated deletion. Thus, this multiplex PCR could detect deletion in approximately 50 per cent of DMD/BMD Thai patients. Eighty per cent of the deletions were in the distal part, whereas, 20 per cent were in the proximal part. We are planning to establish other molecular techniques such as linkage analysis, cDNA hybridization and immunostaining of dystrophin protein to improve a mode of diagnosis and management of DMD/BMD patients in the Thai community.

Rapid karyotyping in the second and third trimesters for fetuses at risk of chromosomal abnormalities at Chulalongkorn Hospital.

Transabdominal fetal blood sampling under ultrasonic guidance was performed in 20 fetuses at 18 to 34 weeks gestation. Pure fetal blood was obtained in all cases; 11 from the umbilical veins at the placental cord insertion, 7 from the fetal intrahepatic veins and 2 from the fetal hearts. Rapid karyotype was obtained within 7 days by fetal lymphocyte culture. Chromosomal abnormality was detected in 5 (25.0%) fetuses. Abnormal karyotype was found in 4 of 8 fetuses with structural malformations detected by antenatal ultrasound and in 1 of 5 fetuses of elderly mothers at advanced gestational ages. This suggested that in fetuses at risk of chromosomal abnormality, rapid karyotype should be obtained and fetal blood sampling is justified in the second or third trimester.