Transabdominal chorionic villus sampling in the second and third trimesters of high-risk pregnancies.

Late chorionic villus sampling (placental biopsy) under ultrasound guidance was carried out in 800 (80 per cent) cases in the second trimester and 200 (20 per cent) cases in the third trimester of pregnancy. Out of 1000 placental biopsies, 250 (25 per cent) were performed because of suspicious ultrasonographic findings. Colour Doppler was used to investigate the uteroplacental and fetal vessels in 300 (30 per cent) pregnancies before and after late chorionic villus sampling (CVS). In the same group, mean serum alpha-fetoprotein (AFP) levels increased after sampling in 20 (6.7 per cent) patients. In 20 patients (2 per cent), complications between sampling and delivery were found. A placental haematoma measuring 0.5-1 ml was seen at the sampling site in 4 (0.4 per cent) patients in the second trimester of pregnancy and in 3 (0.3 per cent) in the third trimester. Two (0.2 per cent) demonstrated fever, but there were no instances of chorioamnionitis. There were only three (0.3 per cent) spontaneous abortions 4-6 weeks after late CVS. However, there was no correlation between AFP elevation, placental haematoma, Doppler measurements, and spontaneous abortion. Cytogenetic findings were obtained in 990 (99 per cent) of 1000 placental samplings. We found 60 (6.0 per cent) chromosomal abnormalities. In the group with suspicious ultrasonic findings (250 cases), we found significant oligohydramnios in 125 (50 per cent) and significant polyhydramnios in 60 (24 per cent), and 45 (18 per cent) had chromosomal abnormalities. Among the 60 patients with chromosomal abnormalities, ultrasonographic findings in 10 (16.7 per cent) were detected after the 20th week of pregnancy. There were no significant differences in mean pulsatility index (PI) in the uteroplacental and fetal vessels before and after late CVS. Preliminary data from five trisomic fetuses (three trisomy 21 and two trisomy 18) showed abnormally increased umbilical PI and abnormally decreased middle cerebral artery PI.