Table 2.
Risk of bias assessment of included studies on vitamin D and IVF outcomes in PCOS patients.
| No | Authors (Year) | Study design | Risk of bias tool | Confounding | Selection of participants | Exposure classification | Deviations from intended interventions | Missing data | Outcome measurement | Selection of reported result | Overall risk |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Ko et al. (2022) (2) | Retrospective Analysis | ROBINS-E | Low | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| 2 | Hu et al. (2023) (3) | Clinical & Lab Study | ROBINS-E | Moderate | Low | Low | Low | Low | Low | Low | Low |
| 3 | Piao et al. (2024) (8) | Retrospective + Prospective | ROBINS-E | Moderate | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| 4 | Zhou et al. (2022) (4) | Meta-Analysis of RCTs | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 5 | Omran et al. (2020) (14) | Observational | ROBINS-E | Moderate | Moderate | Low | Low | Low | Low | Low | Moderate |
| 6 | Dastorani et al. (2018) (10) | RCT | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 7 | Lerchbaum et al. (2021) (11) | RCT | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 8 | Pagliardini et al. (2015) (12) | Cross-sectional | Newcastle-Ottawa | Moderate | Moderate | Low | N/A | Low | Low | Moderate | Moderate |
| 9 | Wu et al. (2019) (13) | Cross-sectional | Newcastle-Ottawa | Moderate | Moderate | Low | N/A | Low | Low | Moderate | Moderate |
| 10 | Li et al. (2024) (9) | Review & Experimental | ROBINS-E | Moderate | Low | Low | Low | Low | Low | Low | Low |
| 11 | Anagnostis et al. (2013) (19) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 12 | Arnanz et al. (2022) (20) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 13 | Bakhshalizadeh et al. (2017) (7) | Lab Study (Experimental) | ROBINS-E | Moderate | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| 14 | Bednarska-Czerwinska et al. (21, 74) | Observational | ROBINS-E | Moderate | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| 15 | Bosdou et al. (2019) (22) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 16 | Boyle et al. (2022) (23) | Case Report | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 17 | Butler et al. (2024) (24) | Cross-sectional | Newcastle-Ottawa | Moderate | Moderate | Low | N/A | Low | Low | Moderate | Moderate |
| 18 | Calcaterra et al. (2021) (25) | Observational | ROBINS-E | Moderate | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| 19 | Cozzolino et al. (2020) (26) | Meta-analysis | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 20 | Contreras-Bolívar et al. (2021) (27) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 21 | Iervolino et al. (2021) (28) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 22 | Irani et al. (2017) (29) | RCT | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 23 | Jeon (2023) (30) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 24 | Kalyanaraman and Pal (2021) (17) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 25 | Ko et al. (2022) (2) | Retrospective cohort | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 26 | Kolcsar et al. (2024) (31) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 27 | Kolcsár et al. (2023) (32) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 28 | Kotlyar and Seifer (2023) (33) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 29 | Lerchbaum et al. (2021) (11) | RCT | RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 30 | Li et al. (2024) (9) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 31 | Luddi et al. (2016) (34) | Prospective cohort | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 32 | Maaherra Armstrong et al. (2023) (35) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 33 | Mancini et al. (2021) (36) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 34 | Meng et al. (2023) (37) | Systematic Review & Meta-Analysis | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 35 | Mesinovic et al. (2020) (38) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 36 | Morgante et al. (18) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 37 | Nandakumar et al. (2024) (5) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 38 | Nandi et al. (2016) (39) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 39 | Omran et al. (2020) (14) | Prospective cohort | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 40 | Ota et al. (2023) (40) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 41 | Paffoni et al. (2019) (41) | RCT Protocol | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 42 | Pagliardini et al. (2015) (12) | Cross-sectional | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 43 | Piao et al. (2024) (8) | Mixed (Retrospective + Prospective) | ROBINS-E | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 44 | Rogenhofer et al. (2022) (42) | Prospective cohort | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 45 | Saeed et al. (2022) (1) | Systematic Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 46 | Schröder-Heurich and Von Versen-Höynck (2017) (43) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 47 | Shahrokhi et al. (2016) (44) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 48 | Shen et al. (2017) (45) | Case–control | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 49 | Showell et al. (2018) (46) | Systematic Review (Cochrane) | Cochrane RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |
| 50 | Singh et al. (2023) (47) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 51 | Skowrońska et al. (2016) (48) | Systematic Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 52 | Sparic et al. (2024) (6) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 53 | Süli et al. (2023) Süli et al. (49) | Animal Study (PCOS model) | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 54 | Vanni et al. (2014) (50) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 55 | Várbíró et al. (2022) (16) | Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 56 | Wesselink et al. (2015) (51) | Narrative Review | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | Not Applicable |
| 57 | Wu et al. (2019) (13) | Prospective cohort | Newcastle-Ottawa Scale | Moderate | Low | Low | Low | Low | Low | Low | Moderate |
| 58 | Zhang et al. (2022) (52) | Prospective cohort | Newcastle-Ottawa Scale | Low | Low | Low | Low | Low | Low | Low | Low |
| 59 | Zhou et al. (2022) (4) | Systematic Review (Meta-analysis of RCTs) | Cochrane RoB 2.0 | Low | Low | Low | Low | Low | Low | Low | Low |