Obstetric history - Past history of preterm birth
- Multifetal gestation in the current pregnancy
- Obstetric complications in the current pregnancy (eg, preterm prelabor rupture of membranes, preterm labor, placenta previa or abruption, oligohydramnios/polyhydramnios, preeclampsia)
- Use of assisted reproduction in the current pregnancy
- Past history of surgical management of abortion
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Demographic factors - Non-Hispanic Black or American Indian/Alaska Native race
- Extremes of maternal age (adolescents, females over age 40)
- Lower educational attainment
- Residence in a disadvantaged area
- Structural racism
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Cervical and uterine factors - Short or dilated cervix in the midtrimester
- Prior cold knife conization or loop electrosurgical excision
- Congenital uterine anomaly (septate, bicornuate, unicornuate, uterus didelphys)
- Vaginal (uterine) bleeding in early pregnancy
- Prior dilation and curettage
- Uterine leiomyoma
- Cervical polyp
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| Chronic medical disorder (eg, chronic hypertension, chronic kidney disease, type 1 diabetes mellitus, some autoimmune diseases, chronic anemia, cardiac disease) |
| Infection (eg, asymptomatic bacteriuria, sexually transmitted infection, periodontal disease, malaria) |
Physical and genetic factors - Short stature
- Some genetic variants
- Personal history of preterm birth in the mother
- Family history of preterm birth in the maternal lineage
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Behavioral factors - Cigarette smoking
- Illicit substance use
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Diet, weight, physical activity - Some types of occupational physical activity
- Low and high prepregnancy weight and gestational weight gain
- Undernutrition
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Other - Excessive stress, lack of social support
- Maternal depression
- Lack of prenatal care
- Short interpregnancy interval (<6 months)
- Unhealthy environment (eg, fine particulate matter in air)
- Male fetal sex
- Fetal conditions (eg, certain congenital anomalies, growth restriction, hydrops fetalis)
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