High failure rate of postmortem karyotyping after termination for fetal abnormality

Abstract

Objective: To determine the failure rate of karyotyping from samples taken after termination of pregnancy for fetal abnormality.

Methods: Perinatal autopsy reports over a 12-month period were reviewed to identify those with cytogenetic studies performed after termination of pregnancy for fetal abnormality.

Results: 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.

Conclusion: 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.