Success rate of cytogenetic analysis at the time of second-trimester dilation and evacuation

The aim of this study was to determine the success rate of cytogenetic analysis from specimens obtained at the time of second-trimester termination of pregnancy by dilation and evacuation.

All second-trimester dilation and evacuations performed by a single practitioner at a single institution from 1993 through 1995 were evaluated to pick out those patients in whom biopsy specimens were submitted for cytogenetic analysis. The main outcome studied was the ability to obtain karyotype results for these specimens.

Cytogenetic studies were performed on 258 dilation and evacuation specimens with a median gestational age of 18 weeks (range 13-25 weeks). The indications for termination were fetal aneuploidy (n = 88, 34%), sonographically diagnosed fetal malformations (n = 82, 32%), intrauterine fetal death (n = 67, 26%), oligohydramnios or premature rupture of membranes (n = 16, 6%), and others (hematologic and metabolic disorders, n = 5, 2%). Successful karyotyping was achieved for 99% of specimens obtained at second-trimester dilation and evacuation, with 3 failures of growth (1% failure rate). The failures included a 14-week molar pregnancy, an 18-week fetus with Dandy-Walker malformation, and a 19-week intrauterine fetal death. Of the samples obtained in cases of intrauterine fetal death, 99% (66/67) provided adequate cytogenetic information.

Karyotyping for abnormal second-trimester pregnancies and intrauterine fetal deaths at the time of a dilation and evacuation procedure has a success rate nearing 100%. In contrast to previous reports, our data indicate that it is unnecessary to perform pretermination invasive karyotyping in patients with abnormal second-trimester pregnancies or intrauterine fetal death who elect to undergo dilation and evacuation. Chromosome analysis at the time of termination of pregnancy by dilation and evacuation reduces patient discomfort, risk of infection, and cost while still providing reliable and vital cytogenetic information for future genetic counseling.