Yindi Liu1, Consortium on Thyroid and Pregnancy 2, Robin Peeters1, Arash Derakhshan1, Tim Korevaar1
(1) Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, Netherlands.
(2) Multiple.
Background
Maternal thyroid dysfunction is associated with various adverse pregnancy outcomes, while studies thus far have exclusively been performed in singleton pregnancies.
Objective
We aimed to examine the associations of maternal thyroid function with obstetric and offspring outcomes in multiple pregnancies.
Methods
We collected individual participant data embedded in the Consortium on Thyroid and Pregnancy. Participants with pre-existing thyroid diseases, thyroid medication usage, or no measurements of gestational thyroid function were excluded. We used mixed-effects models to explore the associations of maternal thyroid function with preterm birth, neonatal birth weight, gestational hypertensive disorders, and child IQ.
Results
We included 725 mother-twin or -triplet pairs. There was a U-shaped association of thyroid stimulating hormone (TSH) concentrations with the risk of preterm birth (absolute risk range: 36.1-55.1%; P = 0.01). Higher TSH concentrations were associated with a higher risk of pre-eclampsia with the absolute risk varying from approximately 1.0% at the lowest TSH concentration to 16.3% at the highest (P = 0.03). Higher FT4 concentrations were associated with a lower risk of pre-eclampsia (absolute risk ranging from 25.2% at the lowest FT4 concentration to 0.3% at the highest; P = 0.02). Neither TSH nor FT4 was associated with neonatal birth weight or child IQ.
Conclusion
This study indicates that the association of maternal thyroid function with adverse obstetric outcomes in multiple pregnancies can be different from singleton pregnancies, suggesting management strategies and treatment targets for thyroid dysfunction may need to be specifically adapted for pregnant women with twins or triplets.