There is large body of evidence to show that the risk of early pregnancy loss is higher after IVF-ET than after natural conception. Several hypotheses have been proposed to explain this phenomenon. One of the possible etiopathogetic factors is the patient's age which is significantly higher in women undergoing IVF than in the general population of naturally conceiving women. Immunologic factors have also been suggested. It seems that procedures like ICSI do not increase the risk of spontaneous abortion (SAB) after IVF-ET. Moreover, the proportion of products of conception with chromosomal aberration in cases of SAB following ICSI procedure is not elevated. Many authors point to the problem of iatrogenic luteal defect after IVF-ET. The use of luteal support after IVF-ET is widely recommended. Interestingly, firm evidence is lacking regarding the efficacy of progestagen or hCG supplementation on the risk of SAB after IVF-ET. However the issue of the effectiveness of progesterone support in decreasing the risk of SAB after ART procedures is far from being conclusively resolved--it deserves well planned, randomized studied to be performed.