Pregnancy is a period of physiological stress for the mother and fetus. When endocrine disorders such as hypothyroidism complicate the period of pregnancy it becomes a common soil for maternal and fetal adverse outcomes. Hypothyroidism in pregnancy can be asymptomatic or symptoms such a cold intolerance, dry skin, excessive fatigue, etc may be noticed.

 It is important to remember that absence of symptoms does not exclude the diagnosis of hypothyroidism. Maternal complications of hypothyroidism include increased risk of abortion, gestational hypertension, anemia, abruptio placenta, postpartum hemorrhage, etc. Fetal complications in untreated maternal hypothyroidism include preterm birth, low birth weight, respiratory distress in the newborn. Primary Hypothyroidism can be overt with High

 TSH and low Free T4 values or can be Subclinical with High TSH and Normal Free T4 value. The patient may have a pre-existing diagnosed Hypothyroidism/Subclinical Hypothyroidism before the patient becomes pregnant or it may get diagnosed at the first antenatal visit of pregnancy.

A patient who is already a known patient of Hypothyroidism and on thyroxine (LT4) replacement with TSH in the normal range may require a 30%-50% increase in the dose of thyroxine upon the detection of pregnancy. A patient who gets diagnosed with  Hypothyroidism/Subclinical Hypothyroidism at the first antenatal visit needs to be put on thyroxine (LT4) replacement.  A strict target of TSH less than 2.5 mlU/ml is essential for the first trimester and less than 3mlU for the 2nd and 3rd trimester. TSH and FT4 values can be monitored every month if required.