Table 2 Risk factors tested for association with severe maternal morbidity
Potential covariates for use in risk adjustment | Number of studies that used the variable in risk adjustment | Number of studies with a statistically significant result | Number of studies with a non-significant result | Number of studies where statistical significance was not reported |
|---|---|---|---|---|
Pre-existing clinical | ||||
Heart disease: including CHF,a,b CHD,a,c pulmonary hypertension,a ischemic heart disease,a valvular heart disease,a conduction disorders | 43 (53.1%) | 10 | 0 | 33 |
Sickle cell diseasea | 11 (13.6%) | 1 | 0 | 10 |
Collagen vascular disease: including SLEa,d and rare autoimmune, rheumatoid arthritis and other collagen vascular | 27 (33.3%) | 5 | 0 | 22 |
HIVa | 21 (25.9%) | 3 | 0 | 18 |
Chronic renal diseasea | 37 (45.7%) | 7 | 0 | 30 |
Chronic hypertensiona | 68 (84.0%) | 20 | 0 | 48 |
Chronic diabetesa | 67 (82.7%) | 15 | 1 | 51 |
Chronic lung disease, including asthmaa | 31 (38.3%) | 5 | 1 | 25 |
Thyroid disease, hypothyroidism | 8 (9.9%) | 0 | 0 | 8 |
Maternal soft tissue condition: includes other uterine surgery, fibroids, cervical conditions | 5 (6.2%) | 0 | 0 | 5 |
Pelvis abnormal | 1 (1.2%) | 0 | 0 | 1 |
Gynecological conditions: e.g., endometriosis, PCOS,e peritoneal adhesions | 3 (3.7%) | 0 | 0 | 3 |
Skin and subcutaneous tissues | 1 (1.2%) | 0 | 0 | 1 |
Hospitalization in prior 5 years or during pregnancy | 4 (4.9%) | 1 | 0 | 3 |
Drug abuse:a including amphetamine, opioid, other; one vs multiple substance, cocaine, combination with alcohol or smoking or mental health conditions | 27 (33.3%) | 4 | 1 | 22 |
Alcohol abusea | 16 (19.8%) | 1 | 1 | 14 |
Smoking | 34 (42.0%) | 6 | 7 | 21 |
Mental health, including depression | 16 (19.8%) | 4 | 0 | 12 |
Obesity class, BMI,f weight gain during pregnancy | 40 (49.4%) | 15 | 5 | 20 |
Height | 2 (2.5%) | 0 | 0 | 2 |
Weight gain | 3 (3.7%) | 2 | 1 | 0 |
Liver disorders, including failure, hepatitis B or C | 11 (13.6%) | 2 | 0 | 9 |
Digestive diseases, including IBDg | 9 (11.1%) | 1 | 2 | 6 |
Seizures and other CNSh conditions, e.g., stroke, MSi | 12 (14.8%) | 2 | 0 | 10 |
Blood diseases: including thrombocytopenia, coagulopathy, or anaemia | 16 (19.8%) | 3 | 0 | 13 |
Fluid electrolyte disorders | 2 (2.5%) | 0 | 0 | 2 |
Paralysis | 2 (2.5%) | 0 | 0 | 2 |
Peripheral vascular disorders | 4 (4.9%) | 0 | 0 | 4 |
Weight loss | 2 (2.5%) | 0 | 0 | 2 |
Musculoskeletal conditions | 5 (6.2%) | 0 | 2 | 3 |
Malignancy | 4 (4.9%) | 0 | 0 | 4 |
History of organ transplant | 1 (1.2%) | 0 | 0 | 1 |
High risk summary measure | 28 (34.6%) | 14 | 0 | 14 |
VTE,j anticoagulant use (now or in past) | 4 (4.9%) | 1 | 0 | 3 |
Hyperlipidemia | 1 (1.2%) | 0 | 0 | 1 |
Disorders of the adrenal gland | 1 (1.2%) | 0 | 0 | 1 |
Obstructive sleep apnea | 1 (1.2%) | 1 | 0 | 0 |
Genital herpes | 4 (4.9%) | 0 | 0 | 4 |
Cystic fibrosis | 2 (2.5%) | 0 | 1 | 1 |
Maternal agea | 79 (97.5%) | 31 | 2 | 46 |
Maternal race/ethnicity | 44 (54.3%) | 24 | 0 | 20 |
N = 41 pre-existing clinical covariates | ||||
Obstetrical Antepartum | ||||
Parity (nulliparous vs grand multipara) and combinations with prior cesarean birth | 48 (59.3%) | 16 | 0 | 32 |
Prior cesarean delivery,a number of prior cesareans | 48 (59.3%) | 13 | 2 | 33 |
Prior preterm birth | 4 (4.9%) | 0 | 0 | 4 |
Multiple gestationa | 69 (85.2%) | 15 | 2 | 52 |
Preeclampsia:a including severe, mild, gestational, eclampsia | 47 (58.0%) | 13 | 1 | 33 |
Placental conditions | 25 (30.9%) | 6 | 0 | 26 |
Gestational diabetes | 29 (35.8%) | 4 | 5 | 20 |
Assisted conception: invasive vs. non-invasive, IUI,k ovulation induction, IVF, ICSI,l diagnosed infertility, infertility treatment | 13 (16.0%) | 7 | 0 | 6 |
Neonatal congenital anomalies or cancer | 14 (17.3%) | 0 | 0 | 14 |
Fetal presentation | 14 (17.3%) | 2 | 2 | 10 |
LGAm or SGAn fetus | 14 (17.3%) | 3 | 1 | 10 |
Oligohydramnios/polyhydramnios | 6 (7.4%) | 1 | 0 | 5 |
Male fetus | 5 (6.2%) | 0 | 0 | 5 |
First trimester prenatal care, adequate prenatal care | 17 (21.0%) | 8 | 0 | 9 |
Provider type (at PNC,o delivery) | 4 (4.9%) | 1 | 0 | 2 |
Isoimmunization | 4 (4.9%) | 0 | 0 | 4 |
Number of previous livebirths, number of previous miscarriages/previous miscarriage, ectopic, termination | 4 (4.9%) | 1 | 0 | 3 |
Prior D&Cp | 1 (1.2%) | 0 | 0 | 1 |
History of hemorrhage previous pregnancy | 2 (2.5%) | 2 | 0 | 0 |
History of hypertensive disorder in a previous pregnancy | 1 (1.2%) | 1 | 0 | 0 |
History of SGA | 1 (1.2%) | 0 | 0 | 1 |
Group B streptococcus screen positive | 1 (1.2%) | 0 | 0 | 1 |
N = 22 obstetrical antepartum covariates | ||||
Intrapartum or postpartum | ||||
Bishop score < 6 | 1 (1.2%) | 1 | 0 | 0 |
Unengaged fetal head | 3 (3.7%) | 0 | 0 | 3 |
Uterine rupture, prolapsed cord | 2 (2.5%) | 0 | 0 | 3 |
Hemorrhage | 4 (4.9%) | 1 | 0 | 3 |
Prior stillbirth or infant death | 4 (4.9%) | 0 | 0 | 4 |
Stillbirth | 9 (11.1%) | 0 | 0 | 9 |
Route of delivery: includes labor y/n, operative VD,q cesarean | 35 (43.2%) | 12 | 3 | 20 |
Maternal indication for cesarean | 1 (1.2%) | 0 | 0 | 1 |
Cesarean incision type | 1 (1.2%) | 0 | 1 | 0 |
Induction | 12 (14.8%) | 5 | 0 | 7 |
Cervical ripening | 1 (1.2%) | 1 | 0 | 0 |
Epidural use | 3 (3.7%) | 0 | 0 | 3 |
PROM,r PPROMs | 8 (9.9%) | 0 | 0 | 8 |
Chorioamnionitis or maternal infection | 4 (4.9%) | 1 | 0 | 3 |
Birth day: weekend, night | 6 (7.4%) | 3 | 2 | 1 |
Gestational age at delivery, preterm birth, type of preterm birth | 33 (40.7%) | 6 | 0 | 27 |
Preterm birth spontaneous vs indicated | 2 (2.5%) | 0 | 0 | 2 |
Labor anomalies: prolonged second stage, oxytocin | 5 (6.2%) | 1 | 0 | 4 |
General vs neuraxial anesthesia | 3 (3.7%) | 2 | 0 | 1 |
Perineal trauma | 1 (1.2%) | 0 | 0 | 1 |
Elective delivery | 6 (7.4%) | 0 | 0 | 6 |
Fetal distress not in labor (separate from elective) | 1 (1.2%) | 0 | 0 | 1 |
N = 22 intrapartum/postpartum covariates | ||||
Other patient-level covariates | ||||
Year of childbirth | 29 (35.8%) | 13 | 2 | 14 |
Income | 2 (2.5%) | 1 | 0 | 1 |
Rural | 4 (4.9%) | 2 | 0 | 2 |
Insurance | 39 (48.1%) | 16 | 4 | 19 |
Education | 21 (25.9%) | 7 | 0 | 14 |
SESt | 5 (6.2%) | 1 | 0 | 4 |
Foreign born | 16 (19.8%) | 7 | 1 | 8 |
Language spoken | 1 (1.2%) | 0 | 0 | 1 |
Refugee status | 1 (1.2%) | 0 | 0 | 1 |
Duration of residence | 1 (1.2%) | 0 | 0 | 1 |
Working | 2 (2.5%) | 0 | 2 | 0 |
Married | 13 (16.0%) | 3 | 2 | 8 |
Profession | 1 (1.2%) | 0 | 0 | 1 |
Home birth | 1 (1.2%) | 0 | 0 | 1 |
Transfer in from other hospital | 3 (3.7%) | 0 | 0 | 3 |
N = 15 other patient-level covariates | ||||
Hospital-level covariates | ||||
Hospital level of maternal care | 2 (2.5%) | 1 | 1 | 0 |
Hospital size or delivery volume | 17 (21.0%) | 6 | 3 | 8 |
Hospitalist | 1 (1.2%) | 0 | 1 | 0 |
Hospital ownership | 11 (13.6%) | 4 | 2 | 5 |
Hospital teaching | 15 (18.5%) | 5 | 2 | 8 |
Hospital urban/rural | 9 (11.1%) | 2 | 2 | 5 |
Hospital percent high-risk | 1 (1.2%) | 1 | 0 | 0 |
Hospital percent non-White | 1 (1.2%) | 1 | 0 | 0 |
Hospital black-serving | 1 (1.2%) | 1 | 0 | 0 |
Hospital percent Medicaid | 3 (3.7%) | 1 | 0 | 2 |
Hospital coding intensity | 1 (1.2%) | 1 | 0 | 0 |
Hospital percent midwife births | 1 (1.2%) | 0 | 1 | 0 |
NICUu level | 4 (4.9%) | 2 | 1 | 1 |
Hospital cesarean rate general endotracheal anesthesia | 1 (1.2%) | 0 | 0 | 1 |
Hospital epidural rate | 1 (1.2%) | 0 | 0 | 1 |
Hospital induction rate | 1 (1.2%) | 0 | 0 | 1 |
Hospital percent NTSVv | 2 (2.5%) | 0 | 0 | 2 |
Hospital percent early elective deliveries | 2 (2.5%) | 0 | 0 | 2 |
Hospital Clinical Processes of Care quintiles | 1 (1.2%) | 0 | 0 | 1 |
Hospital Patient Perspectives of Care quintiles | 1 (1.2%) | 0 | 0 | 1 |
Hospital number triaged per day | 1 (1.2%) | 0 | 0 | 1 |
Hospital number triaged per delivery | 1 (1.2%) | 0 | 0 | 1 |
Hospital > 4 hospitals within 20 miles of residence | 1 (1.2%) | 0 | 0 | 1 |
Hospital excellent doctor:nurse relationship | 1 (1.2%) | 0 | 0 | 1 |
Hospital doctors/1000 deliveries | 1 (1.2%) | 0 | 0 | 1 |
Hospital MFMw on staff | 1 (1.2%) | 0 | 0 | 1 |
Hospital midwives available | 1 (1.2%) | 0 | 0 | 1 |
Hospital anesthesia available 24/7 | 1 (1.2%) | 0 | 0 | 1 |
Hospital anesthesia staff have no other responsibilities | 1 (1.2%) | 0 | 0 | 1 |
Hospital equivalent staffing day and night | 1 (1.2%) | 0 | 0 | 1 |
Hospital cesarean in main hospital operating room | 1 (1.2%) | 0 | 0 | 1 |
Hospital radiology available 24/7 | 1 (1.2%) | 0 | 0 | 1 |
Hospital blood bank available24/7 | 1 (1.2%) | 0 | 0 | 1 |
Hospital massive transfusion protocol in place | 1 (1.2%) | 0 | 0 | 1 |
Hospital pharmacist dedicated to L&Dx | 1 (1.2%) | 0 | 0 | 1 |
Hospital Bakri Balloon available | 1 (1.2%) | 0 | 0 | 1 |
Hospital epidural easy to get | 1 (1.2%) | 0 | 0 | 1 |
Hospital adult critical care 24/7 | 1 (1.2%) | 0 | 0 | 1 |
Hospital subspecialty intensive care units available | 1 (1.2%) | 0 | 0 | 1 |
Hospital difficult to get consults | 1 (1.2%) | 0 | 0 | 1 |
Hospital has NICU | 1 (1.2%) | 0 | 0 | 1 |
Hospital central FHRy monitoring | 1 (1.2%) | 0 | 0 | 1 |
Hospital emergency response team available to L&D | 1 (1.2%) | 0 | 0 | 1 |
Hospital allow TOLACz | 1 (1.2%) | 0 | 0 | 1 |
Hospital 100% of cesareans begun within 30 min | 1 (1.2%) | 0 | 0 | 1 |
Hospital intermittent FHR monitoring < 50% of patients | 1 (1.2%) | 0 | 0 | 1 |
Hospital doctors sign out to each other | 1 (1.2%) | 0 | 0 | 1 |
Hospital formal rounds are conducted on L&D | 1 (1.2%) | 0 | 0 | 1 |
Hospital drills and simulations required | 1 (1.2%) | 0 | 0 | 1 |
Hospital FHR monitoring course required of doctors | 1 (1.2%) | 0 | 0 | 1 |
Hospital tracking of haemorrhage occurs | 1 (1.2%) | 0 | 0 | 1 |
Hospital tracking of infection occurs | 1 (1.2%) | 0 | 0 | 1 |
Hospital tracking of 3rd & 4th degree lacerations occurs | 1 (1.2%) | 0 | 0 | 1 |
Hospital has cesarean evaluation team | 1 (1.2%) | 0 | 0 | 1 |
Hospital allows maternal transfers in | 1 (1.2%) | 0 | 0 | 1 |
Hospital has a protocol for induction of labor | 1 (1.2%) | 0 | 0 | 1 |
Hospital has a protocol for cesarean delivery | 1 (1.2%) | 0 | 0 | 1 |
Hospital gives education regarding induction of labor | 1 (1.2%) | 0 | 0 | 1 |
N = 58 hospital-level covariates | ||||
Community-level covariates | ||||
Region | 21 (25.9%) | 6 | 1 | 14 |
Neighborhood poverty | 3 (3.7%) | 0 | 2 | 1 |
Miles from zip code to hospital | 1 (1.2%) | 0 | 1 | 0 |
Geographic designation of area urban/rural | 8 (9.9%) | 2 | 0 | 6 |
County frequency of obstetricians/anesthesiologists | 1 (1.2%) | 0 | 1 | 0 |
County frequency of births to teens | 1 (1.2%) | 0 | 1 | 0 |
County frequency of unmarried women | 1 (1.2%) | 0 | 1 | 0 |
County frequency of divorced females | 1 (1.2%) | 0 | 1 | 0 |
County frequency of female family heads | 1 (1.2%) | 0 | 1 | 0 |
County frequency of females with no insurance | 1 (1.2%) | 0 | 1 | 0 |
County frequency of foreign-born persons | 1 (1.2%) | 0 | 1 | 0 |
County frequency of persons with less than high school education | 1 (1.2%) | 0 | 1 | 0 |
County frequency of non-White persons | 1 (1.2%) | 0 | 1 | 0 |
County household income measure | 18 (22.2%) | 4 | 2 | 12 |
County frequency of unemployed persons | 1 (1.2%) | 0 | 1 | 0 |
County frequency of food stamp beneficiaries | 1 (1.2%) | 0 | 1 | 0 |
County frequency of persons with no phone | 1 (1.2%) | 0 | 1 | 0 |
County frequency of households with > 1 person/room | 1 (1.2%) | 0 | 1 | 0 |
County number of days with good air | 1 (1.2%) | 0 | 1 | 0 |
County number of deaths due to AIDSaa | 1 (1.2%) | 0 | 1 | 0 |
County number of deaths due to MVAbb | 1 (1.2%) | 0 | 1 | 0 |
County death suicide | 1 (1.2%) | 0 | 1 | 0 |
N = 22 community-level covariates | ||||
TOTAL: N = 180 covariates | ||||