Twins vs singletons—Long-term health outcomes

Introduction: Multiple gestations are a risk factor for most pregnancy complications. The current study aimed to study whether offspring born after twin pregnancies are at increased risk for long-term health complications. Material and methods: A retrospective cohort study was conducted in a large medical center, including all offspring born between the years 1991–2021, which were followed-up until 18 years of age. Hospital-based diagnoses of the offspring were categorized into main groups of morbidities: cardiac, respiratory, infectious, neurological, malignancy, and metabolic. Incidence of hospitalization with diagnoses from each main group was compared between twins and singletons, as well as time to first hospitalization. Cox proportional hazard models were used to study the association between twins vs singletons and hospitalizations by grouped morbidities, while adjusting for maternal age, ethnicity and gender, besides maternal recurrence in the cohort. Results: A total of 369 478 offspring were included in the analysis; of these 11 986 (3.2%) were twins and 357 492 (96.8%) were singletons. Twins were more likely to be delivered preterm (odds ratio = 17.65, 95% CI: 16.74–18.60), by cesarean delivery and following infertility treatments. Incidence of hospitalizations with all morbidity groups was slightly, some significantly, higher among twins, including cardiac: 1.9% vs 1.5%, respiratory; 8.4% vs 7.1%, neurological: 7.7% vs 7.4%, infectious: 26.0% vs 24.1%, and malignancies: 0.7% vs 0.4%. The risk remained higher in the multivariable analyses (adjusted hazard ratios ranging between 1.09–1.75). When stratifying by gestational age at delivery, the risk for most morbidities was lower among twins vs singletons born in similar gestational ages. Conclusions: Twins as compared to singletons are at increased risk for most morbidities due to their risk of being born earlier.