There is a definitive link between endometriosis and infertility. The exact reason for this is unclear. However endometriosis is seen in about 20 to 35% of women referred to the fertility clinics worldwide.
It is thought that endometriosis can affect fertility in various ways as it:
- Can make sex very painful and difficult.
- Distorts the pelvic organs
- Changes the position of tubes and ovaries and creates adhesions
- Alters hormonal function
- Interferes with Ovulation
- Creates a hostile inflammatory environment
- Decreases Ovarian reserve (lowers AMH)
- Causes decreased implantation of the fertilized egg
The severity of the effect on fertility is related to the location, size and severity of the endometriotic deposits and the degree of distortion of the pelvic organs. Many different scoring systems have been used to assess the severity of endometriosis and the probable impact on fertility (American Fertility Society). None of these have a very strong predictive value in assessing the impact on fertility.
Surgical treatments for endometriosis, the division of adhesions and restoration of normal pelvic anatomy imay mprove pregnancy rates and may facilitate oocyte retrieval at IVF.
Excision or ablation of endometriosis can both improve pregnancy rates.
We must however, be realistic. The effect of surgery on natural fertility is not as great as we would like. Most studies have shown only a modest positive effect of surgery on natural fertility and some have shown no effect. It is also possible to do harm by damaging the ovaries during surgery thus negatively impacting future fertility rates.
An open and honest discussion on these issues is really important. Where fertility is the main issue it is crucial that the goals of the surgery are clearly defined before the operation.
IVF treatment removes gametes (sperm and oocytes) from the hostile, inflammatory, pelvic environment created by endometriosis and thereby maximises the chances of conception. Sometimes patients with endometriosis should not have surgery but go straight to IVF. In some women the surgery may be performed with the specific goal of trying to improve IVF outcomes.
Following surgery it is probably advisable to start trying to get pregnant without delay! Evidence suggests that pregnancy rates are highest in the first six months following surgical treatment. In addition, there is evidence that women with endometriosis have an earlier decline in their fertility with age and an earlier menopause.
The decision when to try start trying to conceive may be assisted by tests such as a baseline FSH and Anti-Mullerian Hormone (AMH) as they give some idea of ovarian reserve and future fertility chances.
If women are not pregnant within 6 months of trying and are over 35 it is probably best to proceed straight to IVF, as fertility will only decline over time.
Compared to other patients, there is some evidence that pregnancy rates in IVF may be lower in women with endometriosis. There is evidence that women require a higher dose of drugs to stimulate the ovaries in endometriosis.
Ovarian reserve may be decreased in women with severe endometriosis and stimulation of ovaries may produce fewer eggs.
There is evidence that in cases of severe endometriosis, long suppression of ovaries by GnRH analogues may improve implantation. Before proceeding to the first IVF cycle, women are given three courses of Gonapeptyl after which they are started on the IVF drugs. This is a variation of the long protocol for IVF. The AMH level may also be useful as it allows fine tuning of the IVF drug dose and may improve pregnancy rates.
This may sometimes be preceded by surgery for severe endometriosis when large endometriomas are drained and the ovaries repositioned. Operating on small endometriomas is best avoided especially in the presence of a low AMH level as it may further decrease ovarian reserve.