Pregnancy and the thyroid


Thyroid hormone production increases during pregnancy. 

Thyroid dysfunction is common during pregnancy causing both hyper and hypo thyroidism. 

Both of which are associated with adverse pregnancy and perinatal outcomes. 

Accurate assessment of thyroid functions and management of thyroid dysfunction in pregnancy is crucial to optimize maternal-fetal outcomes.

There is a modest reduction in the upper range of normal for thyrotropin in late first trimester pregnancy. 

Total T4 studies in pregnancy are less accurate and measures about 1 1/2 times nonpregnant values.

Total T4 levels a more accurate than free T4 during pregnancy.

Women with treated hypothyroidism who become pregnant should increase their Levothyroxin dose by 20 to 30%.

For the treatment of Graves’ disease during pregnancy, propylthiouracil is recommended through 16 weeks gestation.

Hypothyroidism is associated with pregnancy loss, premature birth, low birth weight, and lower offspring IQ. 

Subclinical hypothyroidism in particular with associated thyroid peroxidase antibody positivity, has been shown to increase risk of pregnancy loss and perinatal complications and lower offspring IQ. 

Levothyroxine therapy improves outcomes for pregnant women with overt hypothyroidism, but data for subclinical hypothyroidism is not consistent.

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