From the Research
Fetal goiter is the most common fetal sign in uncontrolled maternal Graves' disease. When a pregnant woman has poorly controlled Graves' disease, thyroid-stimulating immunoglobulins (TSIs) can cross the placenta and stimulate the fetal thyroid gland, leading to fetal hyperthyroidism. This excessive thyroid stimulation causes the fetal thyroid to enlarge, resulting in goiter formation. The goiter can be detected on ultrasound as early as the second trimester. While fetal growth restriction can occur in cases of maternal thyroid dysfunction, it is not as specific or common as goiter in the context of Graves' disease, as noted in a case report where fetal hyperthyroidism was treated with maternal administration of methimazole 1.
Key Points to Consider
- Fetal goiter is a direct consequence of the transplacental passage of thyroid-stimulating immunoglobulins from the mother to the fetus.
- The management of maternal Graves' disease during pregnancy involves maintaining the mother's thyroid hormone levels in the high-normal range using antithyroid medications such as propylthiouracil or methimazole, as discussed in the management of fetal and neonatal Graves' disease 2.
- Regular monitoring of maternal thyroid function and fetal ultrasound assessments are crucial for early detection and management of complications, including the adjustment of antithyroid drug doses to prevent fetal hypothyroidism and goiter, as seen in cases where reduction of maternal ATD dose and injection of levothyroxine intra-amniotically resolved the goiter 3.
- In cases of suspected fetal hyperthyroidism, close monitoring and potentially adjusting the maternal treatment regimen can help mitigate risks to the fetus, as demonstrated by the successful treatment of fetal hyperthyroidism through oral maternal administration of methimazole 1.
Clinical Implications
The presence of fetal goiter in the context of uncontrolled maternal Graves' disease underscores the importance of meticulous management of the mother's thyroid function to prevent complications in the fetus. This includes careful selection and dosing of antithyroid medications, regular monitoring of both maternal and fetal thyroid status, and prompt intervention should complications arise. The most recent and highest quality study 4 highlights the potential for neonatal Graves disease and associated complications, emphasizing the need for vigilant monitoring and management throughout pregnancy and into the neonatal period.