Cord blood thyroid-stimulating hormone level in twin pregnancy.

Background: Cord blood thyroid-stimulating hormone level is elevated among neonates who undergo more perinatal stress. The aim of this study was to investigate the effect of twin pregnancy on the cord blood thyroid-stimulating hormone level.

Methods: The study group consisted of 24 910 singleton and 543 twin neonates over a 4-year period. The effect of twin pregnancy on the cord blood thyroid-stimulating level was evaluated. Linear regression analysis was used to control for the effect of mode of delivery, birth weight, and infant sex.

Results: The median cord blood thyroid-stimulating hormone levels (interquartile range) in the singletons and in the twins were 5.8mIU/l (4.2-8.6) and 5.6mIU/l (4.3-7.5), respectively. Linear regression analysis revealed no significant difference between singleton and twin cord blood thyroid-stimulating hormone levels (p = 0.23). Cord thyroid-stimulating hormone levels tended to be higher in second-born twins (p = 0.08) and monochorionic twins (p = 0.097) compared with singleton neonates. Twins with more than 20% weight discordance were associated with a significantly higher cord blood thyroid-stimulating hormone level (p = 0.035).

Conclusion: Cord blood thyroid-stimulating hormone level is elevated in some subgroups of twins who are at higher risk of adverse perinatal outcomes. However, the overall effect of multiple pregnancy on the cord blood thyroid-stimulating hormone level is small. Cord blood thyroid-stimulating hormone screening for congenital hypothyroidism is also valid in twin pregnancies.