Endometriosis Causing Infertility

Frederick R. Jelovsek MD

How endometriosis causes infertility is not fully known. Most physicians believe that endometriosis affects fertility only when the endometriotic lesions cause scarring. This scarring in turn decreases the ability of the fallopian tube to pick up an egg where it will be fertilized by the sperm and transported to the inside of the uterus for implantation. The more extensive the scarring, i.e., the more severe the endometriosis, the more likely for infertility to be caused by the endometriosis.

This was not totally the case according to Pal and others. In this recent study, Pal L, Shifren JL, Isaacson KB, Chang Y, Leykin L, Toth TL: Impact of varying stages of endometriosis on the outcome of in vitro fertilization-embryo transfer. J Assist Reprod Genet. 1998; 15(1): 27-31, they found that patients with more severe endometriosis had eggs that didn't fertilize as well (in the "test tube") as did those from patients with milder disease. The number of eggs that were stimulated and harvested in each group were the same and the fertilized eggs that were transferred to the uterus and subsequently developed were the same in both groups. The only difference was that in patients with mild endometriosis, more of their eggs were fertilized than in patients with more severe (Stage 3 and 4) endometriosis.

This study suggests that there is a biological impact of some sort on the eggs (while still in the ovary) by severe endometriosis that makes the "less fertilizable". It may be that IVF may compensate for or overcome this reduction in the biological potential of the oocytes associated with severe disease if multiple eggs are obtained.