Deep endometriosis is considered the most severe form of endometriosis. It is commonly associated with severe pelvic pain and infertility. As regards the latter, severe distortion of the pelvic anatomy due to adhesions and chronic inflammation are key mechanisms. Other than primary IVF, deep endometriosis surgery is a useful tool, as it can increase chances of spontaneous conception in appropriately selected cases (where no other factors, such tubal pathology or male-related infertility, exist). It needs to be remembered, though, that this type of surgery (laparoscopic or robotic) is highly challenging and requires a significant level of expertise, therefore, it should be performed in highly specialised referral centres. In this way, risk of complications can be lowered, and positive outcomes maximised.

Most of the published evidence refers to surgery for deep endometriosis of the bowel and bladder. Although results may vary between studies, one may expect pregnancy rates of 60% or higher after surgery, with the majority of those being natural conceptions. Similar outcomes may be achieved in patients with known endometriosis- related infertility, although several other factors may also play a role, such as duration of infertility, co-existence with other conditions (adenomyosis, ovarian endometrioma), age, ovarian reserve, and route of surgery. Although the role of surgery pre-IVF is not in the scope of this article, performing surgery in infertile patients with multiple failed IVFs appears to increase conception chances, even natural conceptions.

A reasonable alternative would be first-line IVF. Indeed, satisfactory pregnancy rates can be achieved following IVF. However, surgery offers the advantage of significantly improving pelvic pain in symptomatic patients.  Moreover, several other points should be discussed with deep endometriosis patients that decide to undergo IVF. Worsening of pelvic pain may occur in patients undergoing ovarian stimulation. Although rare, increase in the size of deep endometriosis nodules may also happen, leading to potentially serious complications such as bowel occlusion or obstruction of ureters and silent kidney loss. An increase in the size may also render less radical surgical procedures particularly challenging, or even not possible.

Fear of surgical complications may keep some patients with pain and pregnancy intention, away from surgery. This should be avoided, as two things need to be remembered: performing such surgery by appropriately-trained endometriosis surgeons reduces significantly the risk of serious complications. Secondly, although the data are limited, it appears that serious complications (if they occur after deep endometriosis surgery) do not appear to have a negative impact on chances of conception. As regards the second, caution should be exercised and consideration of IVF after surgery given, particularly in septic complications.

In summary, deep endometriosis surgery (when performed by appropriately trained surgeons) can increase the chances of spontaneous conception. This approach should be favoured in patients with pelvic pain and pregnancy intention, with or without known infertility. The role of surgery in patients without pain, for the sole purpose of restoring fertility is currently not clear. An ongoing debate between primary IVF and first-line surgery should hopefully be resolved, once high-quality, ongoing randomized controlled trials comparing the two approaches report their results.