Potashnik 1999.

Methods	Retrospective cohort.
Participants	The study cohort included 1197 subfertile women attending a subfertility clinic in Beer‐Sheba, Israel, between 1960 and 1984, of whom 780 were exposed to fertility treatment. Mean follow‐up, 17.9 years.
Interventions	Any drug; clomiphene citrate. Data on dosages and number of cycles were available.
Outcomes	Histologically confirmed endometrial cancer was retrieved by linkage of the cohort to the Israel National Cancer Registry through 1994. Incident cases in total cohort, 2; in exposed cohort, 2.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Selection bias (comparability)	High risk	Comment: Exclusion of endometrial cancer cases at the beginning of the study was not reported. Comment: Non‐exposed women drawn from the same population as exposed cohort. Quote: "No statistically significant differences were found between the exposed and unexposed groups regarding all types of infertility, ethnic origin, and age at first visit". Comment: No comparability on diabetes mellitus, polycystic ovary syndrome (PCOS), and obesity was ensured.
Selection bias (confounding)	High risk	Quote: "The standardized incidence ratio was computed as the ratio of observed to expected numbers of cases with 95% confidence interval (CI) estimates". Comment: Analyses inadequately controlling for potential confounding factors.
Performance bias	High risk	Comment: Exposure to ovary‐stimulation drugs was ascertained by medical records. Blindness regarding the allocated interventions not guaranteed.
Detection bias	Low risk	Quote: "The study cohort computer file was linked to the Israel National Cancer Registry to identify cancer cases". Comment: Outcome was ascertained by record linkage
Attrition bias	Low risk	Quote: "Cancer ascertainment during internal verifications was found to be 90%–95% complete" Comment: Follow‐up was expected to be rather complete.
Selective reporting (reporting bias)	High risk	Comment: Analyses on endometrial cancer by type of subfertility not reported.
Other bias	High risk	Quote: "The mean (+/‐SD) duration of follow‐up for the study population was 17.9+/‐5.3 years".. Comment: Length of follow‐up was considered adequate. Comment: Non‐RCT study.