It has been well accepted that maternal thyroid dysfunction has adverse affects on both mothers and fetuses. However, the dramatical changes during pregnancy make the interpretation of thyroid function test (TFT, i.e. free triiodothyronine [FT3], free thyroxine [FT4] and thyrotropin [TSH]) very difficult. Previous studies have shown that the level of thyroid hormones differs from non-pregnant population and varies from gestational ages. Moreover, studies have shown the agreement among different instrument platforms was quite low. This study is aimed to determine gestational age specific TFT reference ranges of the local pregnant population for all available platforms currently used under Hospital Authority and Department of Health.

Inclusion Criteria:

• Pregnant women receiving pregnancy and postnatal care in the Department of Obstetrics & Gynaecology, Prince of Wales Hospital, Hong Kong

Exclusion Criteria:

• 1. Previous history of thyroid dysfunction (hypothyroidism or hyperthyroidism);
• 2. Autoimmune disease, particularly those receiving corticosteroid or immunosuppressant: e.g. systemic lupus erythematosus;
• 3. Disease associated with thyroid dysfunction: e.g. molar pregnancy

Gestational age-specific thyroid function reference range

Hong Kong women

To be confirmed.