Cytogenetic studies of spontaneous miscarriages: a seven year study to compare significance of primary vs. secondary culture methods for assessment of fetal karyotype yield and maternal cell contamination.

Primary in-situ culture (PIC) and secondary trypsinized culture (STC) are the two currently used methods for culturing chorionic villi in order to cytogenetically evaluate products of conception (POC) from spontaneous miscarriages. We compare these culture techniques in our laboratory over a period of seven years to evaluate fetal karyotype yield and maternal cell contamination. Data from a total of 2077 cases from 1992-1999 was entered into a data entry program created in Epi Info version 6. Analysis, using the chi square test of significance, was performed in the same program. Our data demonstrated a statistically significant excess of normal female karyotype detected by the STC method and a statistically significant excess of abnormal karyotypes detected by the PIC method. We attribute these findings to the greater risk of maternal cell contamination with the STC method. We conclude that the PIC method is more accurate in detecting the fetal karyotype and the STC method has a higher risk of maternal cell contamination. We suggest that the PIC method should be adopted as the method of choice when evaluating POC by culturing chorionic villi.