Hypothyroidism During Pregnancy: Diagnosis, Treatment and Care

Hypothyroidism develops when the thyroid gland produces insufficient hormones. Thyroxine (T4) and triiodothyronine (T3) are the two key thyroid hormones essential for metabolism and overall health. They are also vital for fetal development during pregnancy, especially for brain and nervous system development.

Untreated hypothyroidism can result in complications such as preeclampsia, preterm labour, and low birth weight. Symptoms include fatigue, weight gain, and increased cold sensitivity. This article analyses how hypothyroidism affects pregnancy and how managing the condition ensures maternal and fetal well-being.

Causes of Hypothyroidism During Pregnancy

Some of the potential causes of hypothyroidism in pregnant women include:

• Pre-existing Hypothyroidism: A pregnant woman with a history of hypothyroidism usually requires a relatively higher dose of thyroid hormones.
• Hashimoto's Thyroiditis: In this autoimmune disease, the immune system mistakenly attacks the thyroid gland, which causes inflammation of the gland and results in the low production of hormones.
• Iodine Deficiency: In iodine-deficient areas, reduced iodine levels lower thyroid hormone synthesis, leading to hypothyroidism. Pregnant mothers require sufficient iodine for normal thyroid function and healthy fetal development.

Symptoms and Signs of Hypothyroidism in Pregnant Women

The symptoms of hypothyroidism during pregnancy often overlap with the symptoms of a normal pregnancy. Therefore, it is challenging to diagnose thyroid disorder. Both share symptoms of fatigue and weight gain, which leads to a delay in diagnosis. 

• Some specific symptoms concerning pregnant women with hypothyroidism are excessive levels of fatigue, sensitivity towards colds, cramping, severe constipation, and impairment of memory or concentration. Such symptoms might persist longer than the usual changes in pregnant women.
• Hypothyroidism also affects the fertility of a woman and increases the risks of miscarriage when it is not treated. 

Detection and treatment of thyroid hormone imbalance, therefore, ensures that both the mother and the fetus stay healthy.

Impact of Hypothyroidism on Pregnancy and Foetus

Pregnancy with hypothyroidism may harm the mother and the foetus simultaneously. 

• In the early stages of pregnancy, the foetal brain development and growth require adequate thyroid hormones in the mother’s body. 
• If the mother suffers from hypothyroidism, problems like high blood pressure, anaemia, miscarriage, premature delivery, and placental abruption might occur.
• In a newborn, thyroid hormone deficiencies may cause problems such as mental retardation, developmental issues, low IQ, or even stillbirth in extreme cases. Growth restriction may also be a cause of low birth weight.
• Thyroid levels in pregnant women should be checked and managed with proper treatment to minimise the risks. Hypothyroidism must be identified and treated early so that fetal development is proper and pregnancy is safe.

Diagnosis of Hypothyroidism in Pregnancy

Monitoring thyroid function is essential in diagnosing hypothyroidism in pregnant individuals, considering the extreme role that thyroid hormones play in determining the health status of the mother and the fetus developing in the womb.

The diagnosis is based primarily on trimester-specific reference ranges for the concentrations of TSH (thyroid-stimulating hormone) and free thyroxine (T4). A TSH level above 2.5 mU/L in the first trimester requires further investigation.

Hypothyroidism Screening Strategies in Pregnancy

Screening for hypothyroidism in pregnancy can vary, but consensus is growing over the importance of universal screening.

• Universal Screening: All pregnant women should undergo TSH testing during their initial antenatal care.
• Selective Screening: Women with risk factors such as age over 30, a history of more than four pregnancies, or a personal or family history of thyroid disease should have their TSH levels evaluated before conception or during their first prenatal visit.
• Follow-up Testing: For patients with hypothyroidism or at risk, testing should be done every 4 to 6 weeks during the first half of pregnancy, with less frequent intervals once stabilised.

Treatment and Management of Hypothyroidism in Pregnancy

Levothyroxine, a synthetic thyroid hormone, is the primary therapy for hypothyroidism during pregnancy.  It helps maintain critical thyroid hormone levels for both mother's health and fetal growth.  Pregnant women often require greater dosages owing to increased thyroid-binding globulin (TBG) and improved thyroid hormone metabolism. 

Following pregnancy confirmation, the dosage of levothyroxine should be raised by 20-30% for women currently on it, depending on TSH levels. The average replacement dosage is 2-2.4 µg/kg/day, and in extreme situations, an initial higher dose may be necessary for quick normalisation. 

Levothyroxine is safe during pregnancy and helps reduce difficulties, including miscarriage and developmental disorders.  Regular monitoring is required, with TSH levels measured every 4-6 weeks in the first half of pregnancy and less often after 20 weeks.  If TSH exceeds the desired range (below 2.5 mIU/L), dose changes may be required.

After delivery, women often resume their pre-pregnancy dosage after thyroid function stabilises.  Effective management entails prompt monitoring and dose modifications to maintain optimum mother and fetal health. 

Importance of Preconception Care

Preconception care is critical for enhancing mother and fetal health by treating health conditions before conception. This includes preconception screening, which analyses health issues including diabetes, hypertension, and thyroid disorders, and advises on lifestyle modifications such as diet, exercise, and avoiding dangerous drugs.

Genetic counselling and vaccine updates are also necessary to avoid issues during pregnancy. For women with hypothyroidism, regulating thyroid hormone levels and carefully monitoring TSH levels before conception is crucial. Patient education on maintaining thyroid function can lower the risk of issues, boosting the odds of a safe pregnancy.

Postpartum Considerations

Postpartum thyroid monitoring is crucial, particularly for women with thyroid abnormalities or those at risk for postpartum thyroiditis (PPT). Thyroid function testing at 3 and 6 months postpartum can identify disorders such as hypothyroidism or thyrotoxicosis. 

Approximately 7-10% of women are afflicted by PPT, especially those with autoimmune thyroid disorders. Long-term therapy of hypothyroidism entails frequent review of thyroid hormone levels and possible modifications to levothyroxine (LT4) doses depending on metabolic and body weight changes.

Monitoring is necessary since some women may develop persistent hypothyroidism. Proper treatment supports thyroid health for both mothers and children.

Lifestyle and Dietary Recommendations

A balanced diet is essential for thyroid health, especially in women with hypothyroidism. Key nutrients include iodine (from iodised salt, dairy, seaweed, and fish), selenium (in Brazil nuts, seafood, and whole grains), and zinc (from nuts, seeds, and legumes). Antioxidant-rich foods like fruits and vegetables support thyroid function.

Stress management practices such as mindfulness, yoga, and meditation help lower cortisol levels, which impact thyroid hormones. Regular exercise, particularly aerobic and strength training, boosts metabolic health and alleviates hypothyroidism symptoms. An adequate diet, stress management, and exercise enhance thyroid function and general well-being.

Conclusion

Early identification and adequate care of hypothyroidism during pregnancy are critical for both mother and fetal health. Timely thyroid function testing and suitable therapy with levothyroxine may avoid difficulties, including preterm labour, miscarriage, and developmental abnormalities in the newborn. 

A healthy diet, stress management, and regular exercise are key to controlling hypothyroidism during pregnancy. Continuous medical follow-up is critical for preserving health, avoiding long-term issues, and ensuring a safe pregnancy. Early intervention is crucial to achieving the well-being of both mother and child.