Mortality and morbidity in very low birth weight infants from twin pregnancies in ireland: a national cohort analysis

INTRODUCTION: Twin pregnancies contribute disproportionately to neonatal morbidity and mortality, primarily due to preterm birth and very low birth weight (VLBW). While studies have yielded conflicting findings on VLBW twins versus singletons, limited research exists in Ireland. This study examines whether survival, neonatal characteristics, and outcomes differ between VLBW twins and singletons in a national cohort.

METHODS: A secondary analysis was conducted using anonymised data from the National Perinatal Epidemiology Centre (NPEC) VLBW audit. The study included all liveborn VLBW infants (401-1500 g and/or 22 + 0 to 29 + 6 weeks' gestation) from singleton and twin pregnancies in Ireland between 2014 and 2022. Maternal and neonatal characteristics were compared using descriptive statistics. Chi-square and t-tests assessed group differences. Poisson regression computed crude and adjusted relative risks (RR).

RESULTS: Of 4766 infants, 29% (n = 1380) were twins and 71% (n = 3386) singletons. Twins were born at higher gestational age (28.38 vs 27.9 weeks, p < 0.001) and had higher birth weight (1087.76 g vs 1059.66 g, p = 0.006). Mortality was lower in twins (15.6% vs 18.9%, p = 0.014), but not after adjustment. Adjusted analyses showed higher risk in twins for delivery room death (RR 1.45, p = 0.013) and severe retinopathy of prematurity (RR 1.47, p = 0.047).

CONCLUSIONS: Although VLBW twins appeared to have better crude outcomes than singletons, adjusted analyses showed broadly comparable survival and morbidity, with specific vulnerabilities. These findings reinforce that twins remain a high-risk population requiring intensive surveillance and proactive management. They also highlight the importance of structured models of care and support the need for updated national guidelines in Ireland to optimise outcomes for both groups.