High failure rate of postmortem karyotyping after termination for fetal abnormality.

Abstract

To determine the failure rate of karyotyping from samples taken after termination of pregnancy for fetal abnormality. Perinatal autopsy reports over a 12-month period were reviewed to identify those with cytogenetic studies performed after termination of pregnancy for fetal abnormality. During the audit period, there were 104 terminations for fetal abnormality. In 89 fetuses, fetal skin (n = 85), placenta (n = 62), or other samples (n = 8) were obtained for postmortem cytogenetic analysis. In 24 (27%) fetuses, postmortem tissues did not yield a karyotype result. The failure rate of post-termination karyotyping was significantly influenced by delivery-sampling interval, but not by gestational age, type of tissue sampled, use of potassium chloride, or aneuploidy. Of the 24 cases for which no post-termination karyotype was obtained, 16 had had successful pre-termination karyotyping, resulting in only eight of 89 (9%) cases in the overall series not having a final karyotype. The high failure rate for post-termination karyotyping suggests that a pre-termination procedure is necessary if parents wish to have almost 100% certainty that cytogenetic information will be available for later genetic counseling.