Reliability of 46,XX results on miscarriage specimens: a review of 1,222 first-trimester miscarriage specimens

Objective To examine the rate of maternal contamination in miscarriage specimens. Design Retrospective review of 1,222 miscarriage specimens submitted for chromosome testing with detection of maternal cell contamination (MCC). Setting Referral centers requesting genetic testing of miscarriage specimens at a single reference laboratory. Patient(s) Women with pregnancy loss who desire complete chromosome analysis of the pregnancy tissue. Intervention(s) Analysis of miscarriage specimens using single-nucleotide polymorphism (SNP) microarray technology with bioinformatics program to detect maternal cell contamination. Main Outcome Measure(s) Chromosome content of miscarriages and incidence of 46,XX results due to MCC. Result(s) Of the 1,222 samples analyzed, 592 had numeric chromosomal abnormalities, and 630 were normal 46,XX or 46,XY (456 and 187, respectively). In 269 of the 46,XX specimens, MCC with no embryonic component was found. With the exclusion of maternal 46,XX results, the chromosomal abnormality rate increased from 48% to 62%, and the ratio for XX to XY results dropped from 2.6 to 1.0. Conclusion(s) Over half of the normal 46,XX results in miscarriage specimens were due to MCC. The use of SNPs in MCC testing allows for precise identification of chromosomal abnormalities in miscarriage as well as MCC, improving the accuracy of products of conception testing.