Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4), prescribed for hypothyroidism, an underactive thyroid gland. During pregnancy, this medication helps manage hypothyroidism, ensuring adequate thyroid hormone levels for both the mother and the developing baby.
The Role of Thyroid Hormones in Pregnancy
Thyroid hormones play an important role in both maternal well-being and fetal development. These hormones are particularly important for the baby’s brain and nervous system, especially during the first trimester. Early in pregnancy, the fetus relies entirely on the mother’s thyroid hormone supply.
The fetal thyroid gland begins producing its own hormones around 12 weeks of gestation, but not sufficient amounts until 18 to 20 weeks. Even after the fetal thyroid becomes active, the mother’s thyroid hormones continue to contribute to the baby’s development throughout pregnancy.
Adjusting Levothyroxine Dosage Throughout Pregnancy
Pregnancy increases the body’s demand for thyroid hormones, often requiring an increase in levothyroxine dosage. This increased need is due to factors like elevated thyroid-binding globulin levels and the transfer of iodine to the fetus. Many pregnant individuals, up to 85%, will require a higher levothyroxine dose.
Frequent monitoring of thyroid-stimulating hormone (TSH) and free T4 levels is important to guide these adjustments. TSH targets for pregnant women are below 2.5 mIU/L, particularly in the first trimester. Doses may need to be increased by 20% to 30% in early pregnancy, and TSH levels should be checked every 4 weeks until mid-pregnancy and at least once around 30 weeks.
Proper Administration and Monitoring
Taking levothyroxine correctly during pregnancy ensures its effectiveness. It should be taken on an empty stomach, 30 to 60 minutes before breakfast. It is also important to separate levothyroxine from other medications and supplements, especially iron and calcium, as these can interfere with its absorption.
Consistent daily dosing is important for maintaining stable thyroid hormone levels. Following delivery, the levothyroxine dose often returns to the pre-pregnancy level. Thyroid hormone levels should be rechecked 4 to 8 weeks postpartum to ensure the dose remains appropriate.
Understanding the Risks of Untreated Hypothyroidism
Leaving hypothyroidism untreated or inadequately managed during pregnancy can lead to several complications for both the mother and the baby. For the mother, risks include preeclampsia, a serious blood pressure condition, gestational hypertension, and anemia. Untreated hypothyroidism can also increase the risk of placental abnormalities and postpartum hemorrhage.
For the baby, untreated maternal hypothyroidism can result in premature birth, low birth weight, and respiratory distress. There is also a risk of impaired cognitive development, including lower IQ, and problems with hearing and speech. Prompt and proper treatment helps mitigate these risks.