Progesterone support of the luteal phase in in vitro fertilization program--a hazard?

To study the effect of progesterone support of the luteal phase in a stimulated cycle a subgroup of our IVF patients was treated with progesterone vaginal suppositoria. The treatment was initiated on the aspiration day. There was no significant difference in the pregnancy or abortion rate between the control group and the gestagen therapy group. However, it seems that progesterone support may increase the pregnancy rate but also the rate of spontaneous abortion. This suggests that the effective and early started progesterone supplementation of the luteal phase may cause the implantation of abnormal nonviable embryos.