The thyroid is a small gland in the front of the neck that helps regulate many important body functions, including metabolism. During pregnancy, healthy thyroid hormone levels are especially important because both you and your baby rely on them.
Thyroid disorders are common among women of reproductive age. Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can affect fertility and may increase the risk of miscarriage or pregnancy complications. Pregnancy itself can also temporarily affect thyroid function.
In the US, thyroid screening is not routinely recommended for every pregnant person, but testing may be done if you have symptoms, risk factors or a history of thyroid disease.
Before pregnancy
If you have experienced infertility or recurrent miscarriages, your healthcare provider may recommend checking your thyroid function.
Treating thyroid disorders before pregnancy can help support fertility and reduce pregnancy risks.
During pregnancy
During pregnancy, your body needs more thyroid hormone. Most people naturally adjust to this increased demand, but some may need treatment or closer monitoring.
Tell your healthcare provider if you:
- have a thyroid condition
- take thyroid medication
- have a family history of thyroid disease
Blood tests may be used during pregnancy to monitor thyroid hormone levels and adjust treatment if needed.
Healthy thyroid hormone levels are important for fetal growth and brain development, especially early in pregnancy.
Hypothyroidism – underactive thyroid
Hypothyroidism occurs when the thyroid does not produce enough hormone. Symptoms may include:
- fatigue
- feeling cold
- constipation
- depression or low mood
Because many of these symptoms are common during pregnancy, blood testing is important for diagnosis. Treatment typically involves levothyroxine (Synthroid® or similar medications), which is considered safe during pregnancy.
If you already take thyroid medication before pregnancy, your dose may need adjustment during pregnancy and should be monitored regularly.
Hyperthyroidism – overactive thyroid
Hyperthyroidism is less common during pregnancy. Symptoms may include:
- rapid heartbeat
- feeling overheated
- nervousness or anxiety
- weight loss
Sometimes pregnancy hormones (especially hCG) can temporarily increase thyroid activity early in pregnancy.
A common cause of hyperthyroidism is Graves’ disease, which may require treatment with anti-thyroid medications during pregnancy.
Some antibodies associated with Graves’ disease can cross the placenta and occasionally affect the baby’s thyroid function, so additional monitoring may be recommended.
For many people, hyperthyroidism improves later in pregnancy.
After pregnancy
Some women develop postpartum thyroiditis, a temporary inflammation of the thyroid that can occur within the first year after delivery.
This condition often begins with temporary hyperthyroidism followed by hypothyroidism. Many people recover completely, but some may need temporary medication or long-term follow-up.
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