Habitual abortions are repeated pregnancies that end in miscarriage of the fetus.

There is no increased risk to the woman unless she has had three or more spontaneous miscarriages (spontaneous abortions). There are various causes for habitual abortions, and some are treatable. An important example is the increased risk of abortion in women with thrombophilia (propensity for blood clots). Recent studies confirm that anticoagulant medication may improve the chances of carrying pregnancy to term.

Robertsonian translocations in one of the partners leads to unviable fetuses that are aborted spontaneously. This explains why a karyogram is often performed in both partners if a woman has suffered repeated abortions.

A controversial area is the presence of increased natural killer cells in the uterus. It is poorly understood whether these cells actually inhibit the formation of a placenta, and it has been noted that they might be essential for this process. A 2004 paper (Moffett et al) warned that determination of NK cells in peripheral blood does not predict uterine NK cell numbers, because they are a different class of lymphocytes, and state that immunosuppressive treatments are not warranted.

References

• Moffett A, Regan L, Braude P. Natural killer cells, miscarriage, and infertility. BMJ 2004;329:1283-5. PMID 15564263.