The traditional definition of habitual abortion (recurrent miscarriage, recurrent pregnancy loss) is the occurrence of three or more consecutive miscarriages (spontaneous abortions) before the 20th week of pregnancy. Some opinions consider two consecutive miscarriages to be sufficient, arguing that there is no difference between two and three spontaneous abortions, either in terms of the likelihood of recurrence or in the underlying risk factors. Single miscarriages occur in 14-19% of clinically diagnosed pregnancies, while habitual miscarriages can affect up to 1-5% of couples who plan to have a child. This figure is much higher for the calculated random "sporadic" occurrence of recurrent miscarriage (<0.3-0.5%). First trimester is referred to as an early miscarriage, after which we talk about late miscarriages. Habitual miscarriage is usually multifactorial in its pathogenesis. The underlying causes may be genetic, anatomical, thrombophilic (a significant proportion of these are genetic), endocrinological, immunological, and infectious. The risk of habitual miscarriage in first-degree blood relatives of affected patients is 2-7 times higher than in controls, confirming the genetic determinants. Also indicating genetic predisposition is the fact that the incidence among siblings of patients with idiopathic habitual miscarriage is twice that of controls.