A study to establish gestation-specific reference intervals for thyroid function tests in normal singleton pregnancy

To establish gestation-specific reference intervals for thyroid function tests in normal singleton pregnancy.

Cross-sectional observational study performed in the Obstetric and Gynaecology department, West Middlesex University Hospital. A single blood sample from 335 pregnant women at various gestations of pregnancy was analysed for thyroid function. FT4, fT3, TSH values at each gestation of pregnancy were calculated.

From the fT3, fT4 and TSH results, a 95% reference interval was calculated for each hormone for each week of pregnancy.

We calculated gestation-specific reference intervals for thyroid function tests throughout pregnancy to facilitate clinical management of thyroid disease in pregnancy.