A comparison of prenatal versus postnatal karyotyping for the investigation of intrauterine fetal death after the first trimester of pregnancy.

Introduction: Aneuploidy is an important cause of intrauterine fetal death (IUFD) after the first trimester. Determination of the fetal karyotype of these pregnancies is commonly done in most units from solid tissues. Results from such techniques are disappointing. The aim of this audit was to compare the results of karyotyping IUFD by invasive testing (amniocentesis or chorionic villus sampling) and solid tissues (skin biopsy).

Subjects And Methods: Women with IUFD managed in our unit between 1 January 1998 and 31 December 2002 (inclusive) were offered either invasive testing before medical induction of labour or solid tissue biopsy after delivery. The amniotic fluid, chorionic villi and biopsies were processed following standard laboratory procedures.

Results: During the 60 months, 230 samples from cases of IUFD were received by the laboratory in our unit; 126 had skin biopsies and 104 underwent invasive testing (81 amniocenteses and 23 chorionic villus sampling). Successful karyotyping was possible in 90% of those who underwent amniocentesis, 100% of those who had chorionic villus sampling and 13.5% of those who had skin biopsies. 50% of skin biopsies were unsuitable for analysis compared to none in the CVS and amniocentesis group. The difference in successful karyotyping between invasive testing and solid tissue testing was statistically significant (P < 0.0001). There were 12 (10.6%) abnormal karyotypes from the 113 successful samples (11/96 in the invasive group versus 1/17 in the solid tissue group).

Conclusion: Invasive testing has a much higher success rate of karyotyping in cases of IUFD and should, therefore, be offered to women presenting with this complication irrespective of gestational age.