Direct chromosome analysis in the second and third trimesters by placental biopsy in 30 pregnancies.

Direct chromosome analysis was performed on placental villi obtained by ultrasound-guided transabdominal needle aspiration in 30 women at between 23 and 37 weeks gestation. Placental biopsy is simple in the presence of severe oligohydramnios where fetal blood sampling is usually more difficult. Direct karyotyping of placental villi is more rapid than chromosomal analysis from fetal blood and from amniotic fluid. Two chromosomal anomalies were discovered: one trisomy 18 and one 6p+. Villus sampling failed in one woman and two samples obtained at 36 and 37 weeks gestation could not be karyotyped. The procedure did not affect the outcome of the pregnancy.