Maternal Morbidity Associated with Early Preterm Birth in Low-Risk Singleton Pregnancies

Background/Objectives: While neonatal morbidities associated with early preterm birth are known, the risks of maternal morbidities in these births remain unclear. Thus, we set out to assess the risk of maternal morbidities associated with early preterm births. Methods: Retrospective cohort study utilizing the United States (US) Natality Live Birth database from the Centers for Disease Control and Prevention (2016-2021). Low-risk singleton pregnancies were included. High-risk conditions such as out-of-hospital births, fetal anomalies, pregestational and gestational diabetes, and hypertensive disorders of pregnancy were excluded. The rates of several maternal morbidities were compared among three gestational age at birth groups: 23 0/7-27 6/7 (i.e., extreme preterm), 28 0/7-33 6/7 (i.e., early preterm), and 37 0/7-41 6/7 (i.e., term, reference group) weeks. Multivariable logistic regression was used to adjust outcomes for potential confounders. Data were presented as adjusted odds ratios (aORs) with a 95% confidence interval (CI). Results: 18,797,394 live births were analyzed. Extreme and early preterm birth were associated with increased odds of maternal transfusion (aOR 3.32, 95% CI 3.13-3.53 and aOR 2.96, 95% CI 2.86-3.07), uterine rupture (aOR 3.75, 95% CI 3.14-4.48 and aOR 4.13, 95% CI 3.76-4.54), unplanned hysterectomy (aOR 5.60, 95% CI 4.85-6.48 and aOR 5.92, 95% CI 5.47-6.40), and maternal admission to the intensive care unit (ICU, aOR 10.58, 95% CI 9.97-11.54 and aOR 10.13, 95% CI 9.77-10.50) compared to term birth. The odds of third- or fourth-degree perineal lacerations were decreased in both preterm birth groups compared to term birth. Conclusions: In addition to the known prematurity-related neonatal morbidities, extreme and early preterm births also impose a risk for maternal morbidities. Higher odds of maternal transfusion, uterine rupture, unplanned hysterectomy, and maternal admission to the ICU were detected in our cohort. These data should be taken into consideration when caring for patients with preterm births.