Table 3.

Risk of bias assessment score for each of the included study.

	1st Author; study year	A	B	C	Aggregate score∗
		Selection	Ascertainment of outcome	Reporting
1	Adegbidi H; 2007	2	2	2	6
2	Alexander G; 1981	1	2	2	5
3	Aluko Olokun; 2015	1	1	2	4
4	Asuquo ME; 2013	1	2	2	5
5	Asuquo, ME; 2010	2	2	2	6
6	Awe OO; 2018	2	2	1	5
7	Bangaly T; 2019	2	2	2	6
8	Chidothe IA; 2014	1	2	2	5
9	Datubo–Brown DD; 1991	1	2	1	4
10	Emadi SE; 2017	2	2	2	6
11	Enechukwu AN; 2020	2	2	1	5
12	Kiprono AS; 2014	2	2	2	6
13	Lookingbill DP; 1995	2	2	1	5
14	Mabula JB; 2012	2	2	2	6
15	Madubuko R; 2018	2	2	2	6
16	Nthumba PM; 2011	1	2	2	5
17	Okafor CO; 2O2O	2	2	2	6
18	Oluwasanmi J, 1969	2	2	2	6
19	Opara KO; 2010	2	2	2	6
20	Oripelaye MM; 2018	1	2	2	5
21	Saka B; 2020	2	2	2	6
22	Shapiro MP, 1953	2	2	2	6
23	Yakubu A, 1993	2	2	2	6

^∗ Aggregate score: 3, 4 (low quality); 5, 6 (high quality).