63 - Epidemiology and Outcomes of Infants Born Late Preterm to Post-term: A Population-Based Study

Publication Number: 2060.63

Brandon d'Eon, Dalhousie University Faculty of Medicine, Halifax, NS, Canada; Haifaa Kashkari, King Abdulaziz University, Faculty of Medicine/Rabigh, Jeddah, Makkah, Saudi Arabia; Tim Disher, IWK Health Centre, West Porters Lake, NS, Canada; John Fahey, Children's Specialized Hospital, Halifax, NS, Canada; Balpreet Singh, Dalhousie University Faculty of Medicine, Halifax, NS, Canada; Victoria Allen, Dalhousie University Faculty of Medicine, Halifax, NS, Canada; Azar Mehrabadi, Dalhousie University, Halifax, NS, Canada; Walid El-Naggar, Dalhousie University, Halifax, NS, Canada

Background: Late preterm, early term and post-term infants are reported to be at higher risk for neonatal complications; however, well-designed studies examining adverse outcomes within these groups on a large population basis are needed.

Objective: Our goal was to compare neonatal morbidity and mortality in infants born late preterm (35+0 - 36+6 weeks gestation), early term (37+0 - 38+6 weeks gestation), late-term (41+0- 41+6 weeks gestation), and post-term (≥42+0 weeks gestation), with those born full term (39+0 - 40+6 weeks gestation).

Design/Methods: This population-based, retrospective cohort study included singleton, live-born infants delivered at ≥35 weeks of gestation in the province of Nova Scotia, Canada between 2010-2023. Infants with major chromosomal or congenital disorders and those with planned palliative care were excluded. Maternal, pregnancy, delivery and resuscitation data, as well as neonatal morbidity and mortality were compared using full-term infants (39+0 - 40+6 weeks gestation) as the reference. Adjusted risk ratios (aRR) and 95% CIs were determined. Statistical significance was p < 0.05.

Results: A total of 106,541 infants (late preterm = 4,727 (4.4%), early term = 31,117 (29.2%), full term = 56,621 (53.1%), late term = 12,566 (11.8%), and post term = 1,510 (1.4%) were included (table 1).

Late preterm infants had higher rates of NICU admissions [aRR (95% CI) 4.83 (4.56 - 5.11)], longer hospital stays [aRR (95% CI) 1.72 (1.65 - 1.79)] and higher risk of death prior to discharge [aRR (95% CI) 4.83 (2.15 - 10.84)] when compared to full term infants. Late preterm infants received more advanced resuscitation at birth and had more respiratory disease, hypoglycemia, need for phototherapy, neurological morbidity, and neonatal infections (table 2).

Early term infants had higher rates of NICU admissions [aRR (95% CI) 1.48 (1.41 - 1.56)], and longer hospital stays [aRR (95% CI) 1.07 (1.05 - 1.09)]. They also had higher rates of resuscitation at birth, hypoglycemia, need for phototherapy, and intraventricular hemorrhage (table 2).

Post-term infants received advanced resuscitation and developed neurological disorders at higher rates when compared to term infants (table 2).

Conclusion(s): This population-based study demonstrates that late preterm and early term infants have higher risks for prematurity-related morbidity compared to term infants. Post-term infants are at higher risk of requiring resuscitation and developing neurological disorders. These findings raise awareness about anticipated risks and better inform health care providers and policy makers seeking to optimize infant care.

Table 1: Maternal, perinatal, and neonatal baseline characteristics
1. n/N (%); Mean (SD); Median (IQR) Median (Q1, Q3); n = N non-missing

Table 2: Adjusted neonatal outcomes of study groups and rates per 1000
Results adjusting for: maternal age; parity; married; delivery method; birth year; chorioamnionitis
PPV: Positive pressure ventilation


Table 2 (continued): Adjusted neonatal outcomes of study groups and rates per 1000
Results adjusting for: maternal age; parity; married; delivery method; birth year; chorioamnionitis