All controlled retrospective and prospective studies that evaluated the effect of surgery (ovarian stripping or cystectomy) on IVF outcome and on ovarian response to gonadotrophin stimulation eligible for inclusion in the review.
Studies in which women received any medical therapy for endometriosis before or after surgery and where the study group was treated by either aspiration of the endometriotic cyst or by oophorectomy were excluded from the review.
The primary outcome of interest was clinical pregnancy rate per cycle. Clinical pregnancy was defined as visualisation of foetal heart activity on transvaginal ultrasound at six weeks or more gestation. Ovarian response to gonadotrophin stimulation was a secondary outcome of interest and was measured by: total number of gonadotrophin ampoules required for ovarian stimulation; number of follicles greater than 14mm in diameter on day 10 of ovarian stimulation; peak oestradiol levels on the day of human chorionic gonadotropin (HCG) administration; and total number of oocytes retrieved. Other outcomes of interest included: fertilisation rate; number of embryos available for transfer; implantation rate; and live birth rate per cycle.
Surgical approaches for endometrioma greater than 3cm were ovarian cystectomy or draining and stripping of the cyst wall. Most procedures were performed laparoscopically. Ovarian stimulation was induced by either recombinant follicle-stimulating hormone (FSH) or human menopausal gonadotrophin (hMG) using various protocols (long, short or ultra short).
Control groups varied and included non-treated endometrioma, tubal factor infertility, aspirated endometrioma, laparoscopically treated peritoneal endometriosis, idiopathic infertility, non-endometriotic benign ovarian cyst and normal non-operated contralateral ovary. Diagnosis of endometrioma was confirmed histologically in the surgery group and/or measurement of CA-125 levels in the control group.
Two reviewers independently performed study selection. Any disagreement resolved by a third reviewer.