Determination of trimester specific reference intervals for thyroid hormones during pregnancy in Malaysian women.

OBJECTIVE To establish trimester specific reference intervals for thyroid hormones during pregnancy in Malaysian women. STUDY DESIGN Cross-sectional observational study performed in the Obstetric Clinic, University Malaya Medical Centre. A single blood sample from 626 women at various trimesters of pregnancy was analyzed for thyroid function. TSH, FT4, TT4, FT3 and TT3 values at each trimester of pregnancy were calculated. RESULTS From the TSH, FT4, TT4, FT3 and TT3 results, reference values based on mean +/- 2SD was calculated for the hormones at each trimester of pregnancy. CONCLUSION We calculated clinically relevant trimester-specific reference values for thyroid function tests through pregnancy to facilitate improved management of thyroid disease in pregnancy in our local population.