Thyroid Disorders and Management During Pregnancy
Thyroid disorders are the second most common endocrine diseases in women of reproductive age, following diabetes. For this reason, obstetricians who provide prenatal care frequently encounter thyroid-related conditions.
When the thyroid gland functions abnormally—either underactive (hypothyroidism) or overactive (hyperthyroidism)—it can lead to significant pregnancy-related risks. Uncontrolled thyroid disease may result in complications such as:
- Miscarriage
- Preterm birth
- Low birth weight
- Intrauterine fetal loss
- Pregnancy-induced hypertension (preeclampsia)
Fortunately, with modern, pregnancy-safe medications, it is possible to regulate thyroid hormone levels effectively, thereby reducing these risks substantially.
Hypothyroidism in Pregnancy and Its Significance
Hypothyroidism, the condition where thyroid hormone production is insufficient, is the most common thyroid disorder observed during pregnancy. The leading cause is often iodine deficiency, which can lead to reduced hormone levels in both mother and baby.
If iodine intake is inadequate:
- The baby’s intellectual development may be negatively affected.
- There is an increased risk of neurological and cognitive impairment.
- The child’s IQ and learning capacity may be lower in later life.
Even mild hypothyroidism—sometimes without obvious maternal symptoms—can pose these risks. Therefore, thyroid function should be monitored and treated regularly throughout pregnancy.
Autoimmune Thyroiditis and Pregnancy
In developed countries, the most common cause of hypothyroidism is autoimmune thyroiditis (Hashimoto’s disease), in which the immune system attacks thyroid tissue. This condition:
- Reduces maternal thyroid hormone levels.
- Negatively impacts fetal brain development, particularly during the first trimester.
- Can lead to long-term neurological consequences if untreated.
Since fetal nervous system development continues throughout pregnancy, consistent thyroid hormone regulation remains essential during later trimesters as well.
Effects of Thyroid Hormones on the Baby
The fetal thyroid gland begins functioning after approximately 12 weeks of gestation. During the first trimester, the fetus is entirely dependent on the mother’s thyroid hormones. Thus, maintaining normal maternal hormone levels early in pregnancy is crucial.
As pregnancy progresses:
- Maternal blood volume increases,
- Hormonal demand rises,
- The dosage of thyroid medication often needs to be adjusted.
Thyroid Screening and the Importance of Early Diagnosis
In the early 2000s, the American College of Obstetricians and Gynecologists (ACOG) recommended thyroid screening only for women with symptoms or a relevant medical history.
However, recent studies have shown that broader screening can be beneficial.
Today, many medical centers recommend testing thyroid hormone levels at the first prenatal visit whenever possible. Early detection and treatment can:
- Improve the baby’s IQ by an average of 4 points,
- Enhance the overall health of the mother,
- Reduce the risks of miscarriage and preterm birth.
Management and Treatment During Pregnancy
Once a thyroid disorder is diagnosed, treatment must be supervised by a physician. With appropriate medication and dosage adjustments, thyroid hormone levels can be maintained within the normal range.
Key principles of treatment:
- Medications used are safe during pregnancy.
- Dosages are adjusted based on maternal blood volume and gestational age.
- Regular monitoring is essential throughout all trimesters.
The greatest benefit is achieved when diagnosis and treatment begin early, particularly during the first trimester. Nevertheless, continuing treatment and follow-up in later stages of pregnancy remains equally important for the health of both mother and baby.
