Table 2.

Quality assessment of included studies based on the Newcastle-Ottawa Scale.

Study (author, y)	Selection				Comparability	Outcome			Quality score
	Representativeness of the exposed cohort	Selection of Non-exposed cohort	Ascertainment of exposure	Demonstration that the outcome of interest was not present at the start of the study	Comparability of cohorts based on the design or analysis #	Assessment of outcome	Was follow-up long enough for outcomes to occur?	Adequacy of the follow-up of cohorts
Wang M et al., 2021 (23)	a)*	a)*	a)*	a)*	c)**	a)*	a)*	a)*	9
Albeitawi S et al., 2022 (24)	a)*	a)*	d)	a)*	d	a)*	a)*	a)*	6
Youngster M et al., 2022 a (25)	a)*	a)*	b)*	a)*	a)*	a)*	a)*	a)*	8
Wang M et al., 2022 (26)	a)*	a)*	a)*	a)*	c)**	a)*	a)*	a)*	9
Youngster M et al., 2022 b (27)	a)*	a)*	a)*	a)*	c)**	a)*	a)*	a)*	9
Aizer A et al., 2022 (28)	a)*	a)*	d)	a)*	d	a)*	a)*	a)*	6
Braga DPAF et al., 2022 (29)	a)*	a)*	a)*	a)*	a)*	a)*	a)*	a)*	8
Adler Lazarovits C et al., 2023 (30)	a)*	a)*	b)*	a)*	c)**	a)*	a)*	a)*	9

Representativeness of the exposed cohort: a) truly representative of the average in vitro fertilization therapy patients in the community, b) somewhat representative of the average in vitro fertilization therapy patients in the community, c) selected group of users, d) no description of the derivation of the cohort. Selection of non-exposed cohort: a) drawn from the same community as the exposed cohort, b) drawn from a different source, c) no description of the derivation of the non-exposed cohort. Ascertainment of exposure: a) secure record, b) structured interview, c) written self-report, d) no description. Demonstration that outcome of interest was not present at the start of the study: a) yes, b) no. Comparability of cohorts based on the design or analysis: a) study controls for female’s age, b) study controls for any additional factors, c) study controls for female’s age and other factors, d) no study controls for female’s age or any other factors. Assessment of outcome: a) independent blind assessment, b) record linkage, c) self-report, d) no description. Was follow-up long enough for outcomes to occur: a) yes, b) no. Adequacy of follow-up of cohorts: a) complete follow-up, b) subjects lost to follow-up unlikely to introduce bias - small number lost ≥ 90% follow-up, c) follow-up rate <90% and no description of those lost, d) no statement.

^# A maximum of 2 stars can be allotted in this category, one for female age, the other for other controlled factors. *, a maximum of one star could be assigned; **, a maximum of two stars could be assigned.