Table 1 Study designs used to limit confounders when investigating the impact of endometriosis on IVF
From: Endometriosis and IVF treatment outcomes: unpacking the process
Study design | Description | Pros | Cons |
|---|---|---|---|
Intrapatient comparisons of the two ovaries | The ovarian response is compared between the affected ovary and the contralateral intact gonad of the same patient | Ovaries in the same conditions | Non informative on pregnancy rate |
Powerful statistics (paired analyses) | Ovarian response in terms of number of follicles is reliable also for retrospective studies. Data on the quality of the oocytes needs prospective recruitment | ||
Matching | Women with endometriosis are matched by age and study period to 1 or more controls (matching 1:1, 1:2 or even more). Matching can be done for other additional variables depending on the investigated item | It allows to study also the impact on clinical pregnancy rate or live birth rate | Residual biases can remain (the intrapatient comparisons are less vulnerable) |
It can be used to study endometriosis in general, not only ovarian endometriomas | The detrimental effects of unilateral lesions can be missed or diluted |