Summary of risk factors and outcomes by risk/association category*
| Outcome | ↑Increased risk or positive association | —No association | ↓Decreased risk or negative association |
| Hypertensive disorders of pregnancy (eight studies) | |||
| Pregnancy-induced hypertension | Rural maternal residency1178 Maternal age 35 years or older and smoked during pregnancy1371 | Continuous smokeless tobacco use2230 Continuous cigarette smoking2230 | Maternal age<35 years and smoked during pregnancy1371 |
| Preeclampsia | Native American maternal race8141 Overweight/obese BMI7372, 835, 836, 837 Age at delivery835,836 Nulliparity835, 836, 837 Gestational diabetes837 Genetic factors (SNPs) CRP_A, rs3093077, (T allele additive)836 MBL2, rs1800451, (T allele dominant) 836 IL1A, rs3273550, (T allele dominant) 836 CTLA4, rs21775, (A allele dominant) 836 CRP, rs3093068, (G allele additive)837 CRP, rs3093068, (G allele dominant)837 CRP, rs876538, (C allele additive)837 CRP, rs876538, (C allele recessive)837 NOS3, rs1799983, (G allele recessive)835 DDAH1, rs10158674, (C allele recessive)835 DDAH1, rs233115, (A allele recessive)835 | Continuous smokeless tobacco use2230 Continuous cigarette smoking2230 Age at delivery 837 BMI8141 Genetic factors (SNPs) GNB3, rs5442, (A allele dominant)835 | Genetic factors (SNPs) CRP_B, rs1205, (A allele dom)836 CRP_C, rs1130864, (T allele dom)836 CRP, rs876538, (C allele dominant)837 NOS3, rs3918227, (A allele dominant)835 |
| Severe preeclampsia | Nulliparity836, 837 Obese BMI836,837 Age at delivery836 Gestational diabetes837 Genetic factors (SNPs) MBL2, rs1800451, (T allele dominant) 836 IL1A, rs3273550, (T allele dominant)836 CTLA4, rs21775, (A allele dominant)836 CRP, rs3093068, (G allele additive)837 CRP, rs3093068, (G allele dominant)837 CRP, rs876538, (C allele additive)837 CRP, rs876538, (C allele recessive)837 | Age at delivery837 | Genetic factors (SNPs) CRP_A, rs3093077, (T allele additive)836 CRP_B, rs1205, (A allele dom)836 CRP_C, rs1130864, (T allele dom)836 CRP, rs876538, (C allele dominant)837 |
| SMM and/or mortality (four studies) | |||
| SMM with transfusions | Native American maternal race119 Any physical health condition119 Any behavioural health condition119 Multiple chronic conditions (two or more)119 | Native American maternal race952 | |
| SMM without transfusions | Native American maternal race119 Rural maternal residency4010 | ||
| SMMM | Rural maternal residency3421 Native American race4010 Medicaid-funded births3421 | Urban maternal residency3421 | |
| Blood transfusions (two studies) | |||
| Blood transfusions | Rural maternal residency3421, 4010 Medicaid-funded births3421 Native American maternal race4010 | ||
| Postpartum haemorrhage (two studies) | |||
| Postpartum haemorrhage | Native American maternal race1331 Gravidity<51131 Birth weight>4500 g1131 Retained placenta1131 Magnesium sulfate use1131, 2944 Antepartum bleeding2944 Previous postpartum haemorrhage2944 Third stage of labour≥20 m2944 Maternal rural residence2944 Fetal macrosomia2944 Oxytocin use>12 h2944 Routine aspirin use2944 Prior uterine incision and vaginal delivery2944 Preeclampsia without severe features without use of magnesium sulfate2944 Parity≥52944 Length of second stage of labour≥1 h2944 Inpatient induction length≥ to 36 h2944h2944 | Prior uterine incision2944 BMI≥402944 Vitamin D supplementation2944 | |
| Other outcomes (four studies) | |||
| Uterine atony | Native American maternal race1331 Birth weight>4500 g1331 | Gravidity<51331 Induction augmentation1331 Chorioamnionitis1331 | |
| Ectopic pregnancy | Maternal age≥19 years1861 Indian Health Service region1861 | ||
| Placental abruption | Continuous use of smokeless tobacco2230 Continuous cigarette smoking2230 | ||
| DIC | Native American race4010 | Rural maternal residency4010 | |
| Hysterectomy | Native American race4010 Rural maternal residency4010 | ||
Significant associations are italicised and bolded, and significant association in the same direction as categorised.
BMI, body mass index; DIC, disseminated intravascular coagulation; h, hours; m, minutes; SMM, severe maternal morbidity; SMMM, severe maternal morbidity and mortality; SNPs, single-nucleotide polymorphisms.