Can I get pregnant with mild hyperthyroidism?

Hyperthyroidism is a disease that poses a great threat to both pregnant women and children, especially to edematous fetuses. If the mother has hyperthyroidism, it is likely to cause fetal hyperthyroidism or neonatal hyperthyroidism. Therefore, if a patient with hyperthyroidism wants to become pregnant, it is best to prepare for pregnancy after the disease is cured. Below, we will introduce you to the relevant knowledge about hyperthyroidism in detail.

1. It is not advisable to get pregnant before hyperthyroidism is cured. Uncontrolled hyperthyroidism increases the incidence of miscarriage, premature birth, stillbirth, placental abruption, etc. in pregnant women, or causes fetal growth retardation, and even hyperthyroid crisis during delivery. Maternal thyroid stimulating antibodies (TSAb) can stimulate the fetal thyroid gland through the placenta and cause fetal or neonatal hyperthyroidism. Therefore, do not rush to get pregnant before hyperthyroidism is cured.

2. Pregnancy can be considered after hyperthyroidism is cured. Generally speaking, those who take medication need to take medication for about 2 years to be cured. After stopping the medication and observing for half a year, if there is no recurrence, pregnancy can be considered; those who are treated with radioactive 131I can consider pregnancy if hyperthyroidism is cured after half a year or a year of treatment; those who are treated with surgery can consider pregnancy if there is no recurrence of the disease 3 months after surgery.

Whether a woman develops hyperthyroidism after becoming pregnant or a woman with hyperthyroidism becomes pregnant, she must receive appropriate treatment. Generally, pregnant women can tolerate mild hyperthyroidism during pregnancy because antithyroid drugs can cross the placenta and affect the thyroid function of the fetus. For those with mild symptoms, antithyroid drugs are generally not needed for treatment. For patients with severe conditions who require treatment, antithyroid drugs are the first choice. There are two main drug treatments for hyperthyroidism: methimazole and propylthiouracil. Propylthiouracil is the preferred choice for the treatment of hyperthyroidism in early pregnancy, while methimazole is the preferred choice for mid- to late-pregnancy. If medication cannot control hyperthyroidism in pregnant women or there are serious adverse reactions after medication, such patients should not be treated with radioactive 131I for hyperthyroidism. Surgery can be performed during the 4th to 6th month of pregnancy. Surgery in early and late pregnancy is prone to cause miscarriage.

The goal of antithyroid drug treatment for hyperthyroidism during pregnancy is to use the minimum effective dose of antithyroid drugs to achieve and maintain serum FT4 at the upper limit of normal values ​​in the shortest possible time, and to avoid antithyroid drugs passing through the placenta and affecting fetal brain development. For example, the commonly used dose of propylthiouracil is 150-300 mg/d. After it is effective, it can be gradually reduced to a maintenance dose of 50-100 mg per day. Thyroid function should be monitored and the drug dosage should be reduced in time.

During the initial stage of treatment for hyperthyroidism during pregnancy, thyroid function should be checked every 2-4 weeks, and then extended to 4-6 weeks. TSH levels may remain suppressed for several weeks after serum FT4 reaches normal levels, so TSH levels cannot be used as a monitoring indicator during treatment. Since the dose of antithyroid drugs for controlling hyperthyroidism needs to be increased after combined use of levothyroxine (L-T4), the combined use of L-T4 during pregnancy is not recommended. Beta-blockers such as propranolol are associated with spontaneous abortion and may also cause complications such as intrauterine growth retardation, prolonged labor, and neonatal bradycardia, so they should be used with caution.

Women with hyperthyroidism can breastfeed after giving birth. Studies have shown that the use of antithyroid drugs during lactation is safe for offspring. The use of propylthiouracil 150 mg/day or methimazole 10 mg/day during lactation has no obvious effect on the infant's brain development, but the infant's thyroid function should be monitored. No complications such as granulocytopenia and liver damage were found in the offspring of mothers who used antithyroid drugs during lactation. Mothers should take antithyroid drugs after finishing breastfeeding and wait 3-4 hours before the next breastfeeding. Methimazole is the first choice for the treatment of hyperthyroidism during lactation.