References for: Causes, evaluation, and treatment.

Medscape Women’s Health 1998 May;3(3):2 (ISSN: 1521-2076) Bick RL; Madden J; Heller KB; Toofanian A

Thrombosis Clinical Center, Department of Medicine (Hematology & Oncology), Presbyterian Hospital of Dallas, Tex., USA.

Impact and Implications of Chromosomal Abnormalities

Role of Chromosomal Anomalies in Recurrent Spontaneous Abortion

In up to 7% of couples with at least 2 spontaneous abortions, one partner carries a balanced chromosome rearrangement.[5] The most common of these is a reciprocal translocation in which a segment of chromosome has exchanged places with a segment of a nonhomologous chromosome. When such a rearrangement is present, the chromosomes have difficulty pairing up and dividing evenly during meiosis. As a result, gametes frequently possess an unbalanced amount of chromosomal material (duplications and/or deficiencies). These imbalances are usually lethal to the developing embryo or fetus, causing spontaneous abortion. Sometimes, the pregnancy continues to term, producing an infant with significant congenital anomalies and mental retardation.

When a parent carries a balanced chromosome rearrangement, the chance of having a live birth with an unbalanced chromosome complement is usually about 1% to 15%. The exact risk depends on the specific chromosomes involved, size of the segment(s) involved in the rearrangement, sex of the transmitting parent, family history, and mode of ascertainment. Therefore, it is quite possible that the couple will have healthy children. In fact, Coulam[6] found a higher incidence of chromosome rearrangement in couples who had experienced both recurrent spontaneous abortion and viable pregnancies than in couples with recurrent spontaneous abortion and no viable pregnancies. When 1 parent carries a chromosome rearrangement, the chance of spontaneous abortion is usually 25% to 50%. Empirical and/or hypothetical data are available for predicting the chance of adverse pregnancy outcome for various rearrangements.[1,7]