Monday 19 November 2007
Fibroids & Fertility
What are the effects of fibroids on fertility, and on the outcomes of assisted reproduction technology, and when is intervention warranted?
According to published estimates, about 30 percent of all women up to the age of 30 years, and half of all women of reproductive age, will develop fibroids. About half of affected women will be asymptomatic. Fibroids are estimated to be associated with infertility in 5-10 percent of women, and are possibly the sole cause of infertility in 2-3 percent. Because most women with fibroids are fertile (and many are asymptomatic), having fibroids does not necessarily mean that reproduction will be compromised. However, it is clear that fibroids could impair fertility and/or cause pregnancy loss, through various possible mechanisms.
These potential mechanisms, include:
-Distortion of the endometrial cavity, preventing or otherwise impeding sperm migration and reducing implantation rates.
-Reduced vascularity and possible discordant growth of endometrial tissue overlying an intramural fibroid, impairing implantation.
-Dysfunctional uterine contractility caused by submucous or intramural fibroids, affecting sperm migration, tubal contractility and embryo nidation.
-Changes in the endometrial cavity milieu, as a result of glandular atrophy or distortion, adenomyosis, separation of muscle fibers from the basal layer of the endometrium, secretion of vasoactive amines, and local inflammatory changes.
Whether or not fibroids affect fertility or the outcomes of assisted reproduction technology (ART) will typically depend on their number, location, and size of fibroids.There is a general consensus that submucous fibroids impede fertility, as well as being associated with miscarriage, and that the obvious benefits of hysteroscopic myomectomy, coupled with its low risks, suggest that the resection of submucous fibroids is warranted to enhance fertility in women with no other obvious cause of infertility or with recurrent pregnancy loss. There is increasing evidence that intramural fibroids may impair the outcomes of ART. Laparoscopic or conventional myomectomy should be carefully considered prior to ART in women with intramural fibroids “of considerable size” in whom other causes of subfertility have been eliminated. Subserosal fibroids, appear from published data to be unlikely to compromise fertility or cause miscarriage, although the number, location and size of the fibroids should be considered in treatment decisions.
Factors to be considered in formulating a plan of management in a subfertile woman with fibroids are an accurate estimation of the size, number and location of the fibroids, and whether or not the uterine cavity/anatomy is distorted. TVS [transvaginal sonography] and hysteroscopy can achieve a sensitivity and specificity of 100 percent in the evaluation of uterine cavity distortion. It is reasonable to consider a hysteroscopic myomectomy for submucosal fibroids in a subfertile woman as this entails relatively little morbidity compared with an open myomectomy. Open myomectomy should be considered where there are large subserosal/intramural fibroids and they are multiple (>5). Patients should be carefully counseled about the intra-operative risks, risks of recurrence of leiomyoma (15 percent), uterine rupture (1 percent), and increased likelihood of caesarean section (50 percent) in future pregnancies.