Objectives

The aim of this study was to evaluate the short- and long-term outcomes of late preterm births in twin pregnancies.

Methods

This retrospective observational cohort study included all women who had twin deliveries between January 1, 2007 and December 31, 2010 by merging the databases of the Korea National Health Insurance claims and National Health Screening Program for Infants and Children. Outcomes were analyzed on a pregnancy level – in one or both twins. The primary short-term outcome was composite morbidity, which included any of the following: transient tachypnea, respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage, and bronchopulmonary dysplasia. The long-term outcomes were defined using prespecified neurological and developmental diagnoses using the International Classification of Diseases-10th Revision code; these were assessed by following up all neonates until the end of 2018, by the time they were 8–11 years of age.

Results

Among 17,189 women who delivered twins at more than 34 weeks of gestation during the study period, 5032 (29.27%) women had given twin birth in the late preterm period. In the multivariate analysis, the late preterm twins had an increased risk for adverse primary short-term outcomes (odds ratio: 2.09, 95% confidence interval: 1.90–2.30), including transient tachypnea (odds ratio: 1.85, 95% confidence interval: 1.64–2.09), respiratory distress syndrome (odds ratio: 2.31, 95% confidence interval: 2.04–2.62), necrotizing enterocolitis (odds ratio: 2.10, 95% confidence interval: 1.20–3.69), and intraventricular hemorrhage (odds ratio: 2.13, 95% confidence interval: 1.46–3.11), compared with the term twins. For the long-term outcomes, the late preterm twins also had an increased risk for any neurological or neurodevelopmental delay (hazard ratio: 1.14, 95% confidence interval: 1.07–1.21).

Conclusions

Our study showed that late preterm twins had an increased risk for short- and long-term morbidities than term twins. These results should be considered when determining the timing of delivery in uncomplicated twin pregnancies.

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