Table 2.

Characteristics of the selected studies in this systematic review.

Authors	Year	Study design	Study design total incidence of AO
			OCP users, females		Non-OCP user, male and females		Non-OCP users, females
			n	(%)	n	(%)	n	(%)
Lilly et al., [12]	1974	Prospective	192	21.4	975	7.9	489	7.2
Schow et al., [13]	1974	Prospective	168	44.6	912	17.0	288	20.5
Butler et al., [14]	1977	Prospective	36	19.4	—	—	174	5.7
Nordenram et al., [15]	1983	Prospective	78	12.8	—	—	78	23.1
Al-Khateeb et al., [16]	1991	Prospective	17	23.5	395	17.5	112	16.1
Larsen et al., [17]	1992	Prospective	16	18.8	86	18.6	36	25.0
Bonine et al., [18]	1995	Prospective	47	27.7	607	11.2	357	12.3
Hermesch et al., [7]	1998	Clinical trial	59	35.6	212	20.8	111	21.6
Garcia et al., [19]	2003	Prospective	87	11.5	—	—	180	3.9
Blondeau et al., [20]	2007	Prospective	111	9.0	305	3.3	80	7.5
Alwraikat et al., [21]	2009	Prospective	245	15.9	842	11.8	341	14.4
Sivolella et al., [22]	2010	Prospective	38	2.6	—	—	80	1.3
Eshghpour et al., [23]	2013	Cross-sectional	66	24.2	190	17.9	52	11.5
Eshghpour et al., [24]	2013	Clinical trial	132	29.5	—	—	158	22.5
Almeida et al., [25]	2016	Retrospective	29	37.9	334	11.7	179	8.9
Bhujbal et al., [26]	2019	Prospective	194	16.0	793	3.8	307	3.9
Nilesh et al., [27]	2019	Prospective	42	16.3	618	7.1	166	6.9