Table 1. Summary Results of Meta-Analyses.
| Outcome | Studies, No. | Source | Pregnancies, No. | Outcomes, No. | Pooled OR (95% CI) | I2, % | τ2 |
|---|---|---|---|---|---|---|---|
| Preeclampsia | |||||||
| Crude | 11 | Barros et al,16 2022; DeFilippis et al,17 2022; Hewawasam et al,18 2022; Mazanowska et al,19 2022; Sobotka et al,20 2021; Madej et al,22 2016; Majak et al,23 2016; Arab et al,24 2015; Bramham et al,26 2013; Coffin et al,27 2010; Pezeshki et al,28 2004 | 70 069 293 | 2 861 580 | 6.34 (4.94 to 8.14) | 67.6 | 0.09 |
| Adjusted (any) | 5 | DeFilippis et al,17 2022; Hewawasam et al,18 2022; Majak et al,23 2016; Arab et al,24 2015; Bramham et al,26 2013 | 31 615 223 | 1 284 691 | 5.83 (3.45 to 9.87) | 77.4 | 0.25 |
| Adjusted for prespecified covariatesa | 3 | DeFilippis et al,17 2022; Hewawasam et al,18 2022; Majak et al,23 2016 | 24 520 251 | 1 011 433 | 4.14 (2.87 to 5.97) | 1.7 | 0.00 |
| Preterm birth <37 wk | |||||||
| Crude | 12 | Craig et al,36 2023; Barros et al,16 2022; Hewawasam et al,18 2022; Sobotka et al,20 2021; Piccoli et al,21 2017; Madej et al,22 2016; Majak et al,23 2016; Arab et al,24 2015; Wyld et al,25 2013; Bramham et al,26 2013; Coffin et al,27 2010; Pezeshki et al,28 2004 | 91 105 532 | 4 919 542 | 7.48 (4.49 to 12.47) | 95.1 | 0.74 |
| Adjusted (any) | 4 | Craig et al,36 2023; Majak et al,23 2016; Arab et al,24 2015; Bramham et al,26 2013 | 46 995 396 | 3 793 167 | 6.65 (4.09 to 12.83) | 81.8 | 0.19 |
| Adjusted for prespecified covariatesa | 3 | Craig et al,36 2023; Majak et al,23 2016; Arab et al,24 2015 | 46 933 949 | 3 793 002 | 5.31 (3.93 to 7.17) | 41.1 | 0.03 |
| Low birth weight <2500 g | |||||||
| Crude | 11 | Barros et al,16 2022; DeFilippis et al,17 2022; Hewawasam et al,18 2022; Mazanowska et al,19 2022; Sobotka et al,20 2021; Piccoli et al,21 2017; Majak et al,23 2016; Arab et al,24 2015; Wyld et al,25 2013; Bramham et al,26 2013; Coffin et al,27 2010 |
73 168 692 | 1 969 495 | 5.50 (3.42 to 8.86) | 91.7 | 0.54 |
| Adjusted (any) | 4 | DeFilippis et al,17 2022; Hewawasam et al,18 2022; Arab et al,24 2015; Bramham et al,26 2013 | 31 944 922 | 972 050 | 6.51 (2.85 to 14.88) | 90.6 | 0.58 |
| Adjusted for prespecified covariatesa | 3 | DeFilippis et al,17 2022; Hewawasam et al,18 2022; Arab et al,24 2015 | 31 943 476 | 971 894 | 4.96 (1.60 to 15.37) | 92.5 | 0.82 |
| Live birth | |||||||
| Crude | 4 | Barros et al,16 2022; Hewawasam et al,18 2022; Wyld et al,25 2013; Bramham et al,26 2013 | 8 263 840 | 8 199 030 | 0.28 (0.03 to 2.61) | 97.8 | 5.02 |
| Adjusted (any) | NA | NA | NA | NA | NA | NA | NA |
| Adjusted for prespecified covariatesa | NA | NA | NA | NA | NA | NA | NA |
| Preterm birth <32 wk | |||||||
| Crude | 4 | Hewawasam et al,18 2022; Piccoli et al,21 2017; Wyld et al,25 2013; Bramham et al,26 2013 | 5 717 636 | 99 507 | 14.47 (8.29 to 25.28) | 80.5 | 0.25 |
| Adjusted (any) | 2 | Hewawasam et al,18 2022; Bramham et al,26 2013 | 2 947 860 | 55 139 | 10.35 (6.89 to 15.53) | 2.7 | 0.00 |
| Adjusted for prespecified covariates | 1 | Hewawasam et al,18 2022 | 2 946 413 | 55 103 | 11.4 (7.41 to 17.55) | NA | NA |
| Birth weight <1500 g | |||||||
| Crude | 5 | Hewawasam et al,18 2022; Piccoli et al,21 2017; Madej et al,22 2016; Wyld et al,25 2013; Bramham et al,26 2013 | 5 717 634 | 78 258 | 4.97 (2.28 to 10.82) | 87.0 | 0.67 |
| Adjusted (any) | 1 | Bramham et al,26 2013 | 1446 | 33 | 7.76 (3.29 to 18.3) | NA | NA |
| Adjusted for prespecified covariatesa | 0 | NA | NA | NA | NA | NA | NA |
| Gestational age | |||||||
| Crude | 5 | Barros et al,16 2022; Mazanowska et al,19 2022; Majak et al,23 2016; Wyld et al,25 2013; Pezeshki et al,28 2004 | 2 769 094 | NA | −3.37 (−3.76 to −2.99)b | 0.0 | 0.00 |
| Adjusted (any) | 0 | NA | NA | NA | NA | NA | NA |
| Adjusted for prespecified covariatesa | 0 | NA | NA | NA | NA | NA | NA |
| Cesarean delivery | |||||||
| Crude | 11 | Craig et al,36 2023; Barros et al,16 2022; Hewawasam et al,18 2022; Mazanowska et al,19 2022; Sobotka et al,20 2021; Piccoli et al,21 2017; Madej et al,22 2016; Majak et al,23 2016; Arab et al,24 2015; Bramham et al,26 2013; Coffin et al,27 2010 | 88 293 100 | 27 376 648 | 3.67 (2.33 to 5.78) | 96.1 | 0.54 |
| Adjusted (any) | 5 | Craig et al,36 2023; Hewawasam et al,18 2022; Majak et al,23 2016; Arab et al,24 2015; Bramham et al,26 2013 | 49 837 531 | 15 991 969 | 3.30 (2.13 to 5.11) | 85.5 | 0.21 |
| Adjusted for prespecified covariatesa | 4 | Craig et al,36 2023; Hewawasam et al,18 2022; Majak et al,23 2016; Arab et al,24 2015 | 49 836 076 | 10 200 179 | 3.06 (1.89 to 4.94) | 86.1 | 0.20 |
Abbreviations: NA, not applicable; OR, odds ratio.
a
Prespecified comorbidities: maternal age and preexisting hypertension.
b
Expressed as mean difference (95% CI) in weeks.