A very large group of patients trying for pregnancy are women experiencing habitual abortions. We have been dealing with these problems in our facilities for years. The most common causes of recurrent miscarriages include genetic disorders, which are, unfortunately, many times not taken into account both by patients and physicians during diagnosis. In such situations, in the first place we recommend karyotype testing and genetic examination of the miscarriage – if we have such opportunity. Genetic disorders should account for 80% of causes of all early miscarriages; this is why these tests are indicated and one should keep it in mind. Unfortunately, physicians often refer the patients for tests for, e.g., antiphospholipid syndrome, which is a very rare cause, and in practice affects less than 1% of patients trying for pregnancy and experiencing miscarriages. Another rare cause of miscarriages are immune disorders, so this factor is also not significant, although we also carry out the diagnosis for this cause in the cases where having diagnosed normal embryos and giving them to couples after preimplantation diagnosis the miscarriages still occur. The factor which is rare but worth considering are hormonal disorders, primarily abnormal level of progesterone and of estrogens in early pregnancy.