Increased incidence of cytogenetic abnormalities in chorionic villus samples from pregnancies established by in vitro fertilization and embryo transfer (IVF-ET).

We studied 201 pregnancies that were established by in vitro fertilization and embryo transfer (IVF-ET) and compared the frequency of cytogenetic abnormalities with that found in a large control population matched for indication group (advanced maternal age) and time of sampling. A total of 252 IVF-ET fetuses were cytogenetically analysed by either chorionic villus sampling (CVS; n = 80) or amniocentesis (n = 172). Eleven chromosome abnormalities were found in the CVS group (13.8 per cent); among them, a 45,X/46,X,dic(Y)(q11)/46,X,del(Y)(q11) mosaic that was found in an IVF pregnancy established by intracytoplasmic sperm injection (ICSI), four cases of trisomy 21, and three cases of trisomy 7 confined to the placenta. The results indicate a statistically significant three- to five-fold increase in both confined placental abnormalities (P < 0.008) and true fetal chromosome anomalies (P < 0.04). In the amniocentesis group, identical rates (1.7 per cent) of chromosome abnormalities were found in the IVF-ET and control groups. It is concluded that late first trimester, but not early second trimester, IVF-ET pregnancies are characterized by an increased frequency of cytogenetic abnormalities found at prenatal diagnosis.