Context: Antenatal hypothyroidism may be associated with an increased risk of developing gestational diabetes mellitus.
Objective: To evaluate whether a TSH value of greater than 2.50 mIU/L in early pregnancy increased the risk of developing gestational diabetes during that same pregnancy.
Design and Setting: Retrospective single centre cohort study of consecutive singleton pregnancies delivering in a multi-ethnic suburban area of Sydney, Australia.
Participants: All pregnant women who underwent antenatal thyroid and gestational diabetes screening and delivered in hospital over the 1 year period 01/01/2016 – 31/12/2016 (n = 1147). Women were grouped and compared by antenatal (first trimester) TSH values.
Main Outcome Measures: Incidence of gestational diabetes mellitus by thyroid status.
Results: Over one quarter of study participants (27.9%) developed gestational diabetes mellitus. Hypothyroidism of pregnancy was observed in 15.9% of women. In multivariable analyses, an antenatal TSH >2.50 mIU/L was not associated with increased risk of developing gestational diabetes mellitus [OR 0.74 (95%CI 0.48-1.16), p=0.68]. Traditional risk factors such as ethnicity, body mass index, past history of gestational diabetes mellitus and family history of type 2 diabetes were strongly predictive of developing gestational diabetes mellitus in the current pregnancy.
Conclusion: A TSH value of greater than 2.5 mIU/L in early pregnancy did not increase the risk of developing gestational diabetes mellitus.