Genetic factors as a cause of miscarriage.

Aneuploidy in the conceptus or fetus, occurs in 5-10% of all pregnancies and is a common reproductive problem in humans. Most aneuploid conceptuses die in utero, resulting in early pregnancy loss. Causes of recurrent miscarriage may include abnormal chromosomes in either partner, particularly translocations, antiphospholipid antibodies and uterine anomalies. Chromosomal aberrations in parents are a major pre-disposing factor and causative of abortion if carried over to the embryo. The transmission rate in the embryo can be speculated to be about 50%. Embryo morphology, developmental rates, and maternal age are correlated with chromosomal abnormalities. Translocation in either partner is one of the most important causes of recurrent miscarriage and the prognosis of subsequent pregnancy in couples with abnormal embryonic karyotype is poorer than that in couples with normal chromosome karyotypes. As for parents whose karyotypes are normal, the frequency of normal embryonic karyotypes significantly increases with the number of previous abortions and a normal karyotype in a previous pregnancy is a predictor of subsequent miscarriage. Recently, many kinds of genetic polymorphisms have also been found to be associated with recurrent miscarriages. In contrast, preimplantation genetic diagnosis for aneuploidy screening is sometimes performed in patients with unexplained recurrent miscarriages. We review genetic factors as a cause of miscarriage.