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.
In the process of in-vitro fertilization (IVF), the normal
mechanisms of fertilization are bypassed because the egg is
harvested from the ovary just prior to ovulation. It is then put
in a "test tube" with sperm where fertilization takes place instead
of in the fallopian tube. The fertilized egg is then implanted
inside the uterus through the vagina and cervix rather than by
way of the fallopian tube. One would expect IVF patients with
endometriosis to fertilize and get pregnant at all the same rate regardless of
the severity of their disease, since the transport system is
being circumvented in IVF.
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.
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