Effects of Low Thyroid Hormone During Pregnancy

Q: My TSH level is 25 in first trimester and have to test T3 and T4. If T3 and T4 comes abnormal, will it affect the baby’s growth and brain? Should we carry it or abort? Kindly suggest. Thanks in advance.
-By Geeta Bisht, 35 years old.


Your TSH level is quite high. Though this suggests hypothyroid state, we require objective measures of T3 and T4 to confirm the diagnosis.

Rarely, the active thyroid hormones may be within range even with elevated TSH. So confirmation of the diagnosis is essential.

Adverse Effects of Hypothyroidism on the Baby

The fetus depends entirely on the mother for the supply of thyroid hormones. It is only after 10- 12 weeks of gestation that it develops its own thyroid gland.

Thyroid hormones are very essential for normal mental development of the fetus. A deficiency of this hormone may lead to low intelligence or reduced motor skills later in life. You may read more about the reduced thyroid hormone during pregnancy.

Unfortunately, we don’t have any method to objectively assess the neural development of the fetus at such an early phase.

Your doctor may require you to get an ultrasound done. On the basis your symptoms and ultrasonography reports, he may comment on the nervous development of the baby.

Treatment of Low Thyroid State in First Trimester

Hypothyroidism needs to be treated at the earliest. Artificial hormone is given from outside as a replacement.

Levothyroxine is the treatment of choice in pregnancy. It is considered safe for the fetus. The dose is adjusted so as to keep the TSH level below 2.5 mU/l.

You will be required to get your hormonal levels checked after every 4-6 weeks throughout pregnancy. The dose may be increased if required.

Close monitoring of fetal growth is also recommended.

Take Care,

Buddy M.D.

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