First trimester pregnancy loss: Clinical implications of genetic testing.

Around 10-15% of pregnancies result in a spontaneous first trimester miscarriage, which is most frequently caused by chromosomal abnormalities, mainly aneuploidies. Genetic analysis of pregnancy loss includes conventional G-banding karyotyping and various molecular methods. Apart from variable methodological limitations, the effectiveness of genetic analysis depends on the type and quality of the tested sample. To improve the reliability of genetic testing, we present methods of appropriate collection and pre-laboratory preparation of chorionic villi from first trimester miscarriage. We also discuss issues of maternal cell contamination, placental mosaicism and reciprocal and Robertsonian translocations in the context of interpretation of the results and genetic counseling.