Thyroid problems can be difficult to diagnose in pregnancy due to higher levels of thyroid hormone in the blood, increased thyroid size, fatigue, and other symptoms which are common to both pregnancy and thyroid disorders.
Thyroid hormone is crucial during pregnancy for the healthy development of the fetal brain and nervous system. During the first trimester through the placenta the fetus gets it’s thyroid hormone supply. Around 12 weeks, the baby’s thyroid begins to function autonomously.
A mildly underactive thyroid gland (subclinical hypothyroidism), relates to elevated TSH levels with coexisting normal thyroid hormone concentrations. Subclinical hypothyroidism affects up to 15% of pregnancies in Europe and USA.
Research shows an association between both low and high free thyroxine levels of the mother during pregnancy and low IQ of the child. Though, for long the decision to treat pregnant women based on the value of thyroid stimulating hormone (TSH) was taking place. Studies show that pregnant women with TSH values in 2.5-4.0 mIU/L range have been over-treated.
The new guidelines issued by the American Thyroid Association (ATA) recommend taking into account TPO antibody status when deciding to treat or not subclinical hypothyroidism in pregnant women. Treatment is no longer recommended for TPO negative women with serum TSH values <4.0 mIU/L.
