Table 2.
Summary of Qualitative and Quantitative Results for Assessed Risk Factors
| Risk Factors | Qualitative Synthesis Result | Meta-Analysis Result [OR (95% CI)] |
|---|---|---|
| History and demographic | ||
| Young age | Unclear | Not applicable |
| Old age | Unclear | Not applicable |
| Hispanic | Likely | 1.23 (1.20–1.25) |
| Asian | Definite | 1.39 (1.33–1.46) |
| Native American | Not | Not applicable |
| Black or African American | Unclear | 1.00 (0.78–1.29) |
| Nulliparity | Likely | Not applicable |
| Prior postpartum hemorrhage | Definite | 2.25 (1.02–4.96) |
| Prior cesarean delivery | Unclear | 1.12 (0.96–1.32) |
| Blood group O | Not | Not applicable |
| Calcium channel blocker exposure | Not | Not applicable |
| Antidepressant exposure | Unclear | Not applicable |
| Aspirin exposure | Not | Not applicable |
| Nonsteroidal antiinflammatory drug exposure | Not | Not applicable |
| Doxylamine exposure | Not | Not applicable |
| Maternal comorbidity | ||
| Hypertension | Likely | 1.84 (1.45–2.33) |
| Diabetes | Definite | 1.22 (1.08–1.39) |
| Anemia | Unclear | Not applicable |
| Obesity | Not | Not applicable |
| Leiomyomas | Unclear | 1.31 (0.55–3.10) |
| Liver disease | Not | Not applicable |
| Thrombocytopenia | Not | Not applicable |
| Asthma | Not | Not applicable |
| Elevated uric acid | Unclear | Not applicable |
| Alcohol use disorder | Not | Not applicable |
| Smoking | Not | Not applicable |
| Pregnancy-related | ||
| Polyhydramnios | Unclear | 1.29 (0.94–1.76) |
| Multiple gestation | Likely | 2.16 (1.53–3.06) |
| Malpresentation | Unclear | Not applicable |
| Macrosomia | Unclear | 1.46 (1.35–1.57) (more than 4,000 g) |
| Placental disorders (previa or abruption) | Definite | 2.74 (1.57–4.79) |
| Antepartum hemorrhage | Unclear | Not applicable |
| Stillbirth | Unclear | Not applicable |
| Labor-related | ||
| Chorioamnionitis | Likely | 1.93 (1.56–2.39) |
| Uterine rupture | Likely | 2.35 (1.65–3.35) |
| Predelivery oxytocin exposure | Likely | 1.15 (0.95–1.40) |
| Induction of labor | Likely | 1.23 (1.10–1.39) |
| Prolonged labor | Definite | 1.76 (1.53–2.03) (all labor) |
| 1.31 (1.24–1.38) (1st stage) | ||
| 1.10 (0.82–1.48) (2nd stage) | ||
| Epidural | Unclear | 0.94 (0.72–1.23) |
| Magnesium exposure | Not | Not applicable |
| Tocolytic exposure | Not | Not applicable |
| Delivery-related | ||
| Gestational age | Not | Not applicable |
| Genital tract trauma | Definite | 1.67 (1.28–2.18) (perineal laceration) |
| 2.19 (1.13–4.24) (high vaginal laceration) | ||
| 5.70 (2.56–12.67) (cervical laceration) | ||
| Instrumented vaginal delivery | Likely | 1.67 (1.40–2.00) |
| Cesarean delivery | Unclear | Not applicable |
| Cord blood collection | Not | Not applicable |
| Breastfeeding | Not | Not applicable |
OR, odds ratio.