Prediction of Term Birth in First Nations Women: A Retrospective Cohort Study.

OBJECTIVE: To ascertain factors that predict term birth in a large cohort of First Nations women in their first pregnancy. We also developed a prenatal clinical scoring rule to facilitate calculation of personalized probabilities for term birth. DESIGN: Retrospective cohort study. SETTING: 2000-2022 in Queensland, Australia. POPULATION: 1 350 473 births over the study period, of which 30 509 were First Nations nulliparous women. METHODS: We ascertained factors predicting term birth exclusively within nulliparous First Nations women. Candidate predictors were clinically relevant information available antenatally. We developed an internally validated logistic regression model allocating points for the presence of clinical predictors, facilitating personalized probability of term birth. MAIN OUTCOME MEASURES: Term birth (≥ 37 weeks). RESULTS: There were 27 310 term births and 3489 preterm births. After excluding stillbirths, 89% (27 255/30509) had a term birth and 11% (3254/30509) had preterm birth. Of the preterm births, 57% (1865/3254) were spontaneous and 43% (1389/3254) were medically indicated. Term birth was significantly associated with singleton pregnancies (OR 24.64, 95% CI 20.13-30.17), absence of major fetal abdominal wall (OR 11.19, 95% CI 6.62-18.91) or cardiac abnormalities (OR 2.51, 95% CI 1.90-3.31), maternal age < 30 years, spontaneous conception, nil substance use, non-small for gestational age fetus, female infant sex, absence of amniotic fluid abnormalities, chorioamnionitis (OR 11.22, 95% CI 8.20-15.34), antepartum placental abruption (OR 10.93, 95% CI 8.12-14.70) and major medical co-morbidities. Term birth was associated with ≥ 5 antenatal visits, residence in a metropolitan area and higher socioeconomic status. CONCLUSIONS: Many factors that influence term birth in First Nations women are amenable to culturally safe and responsive supports.