Thyroid and Pregnancy- What you need to know

Thyroid gland is located in the front of the neck below the Adam’s apple and is an essential organ for producing thyroid hormones, which maintains the body metabolism. The thyroid uses iodine to produce vital hormones. Thyroxine, also known as T4, is the primary hormone produced by the gland. Once released into the blood stream to the body’s tissues, a small portion of the T4 is converted to triiodothyronine (T3),  the most active hormone.

Pregnancy results in a number of physiological and hormonal changes that have an effect on the thyroid functioning. The changes mainly occur due to the influence of two main hormones: human chorionic gonadotropin (hCG), and Estrogen, the main female hormone.

Changes during Pregnancy:

The functioning of the thyroid gland should remain normal in a healthy pregnancy. However, some women may develop an underactive thyroid condition called Hypothyroidism or an overactive thyroid condition called Hyperthyroidism.

The thyroid gland can also sometimes increase in size during pregnancy known as Goiter. However, pregnancy-associated goiters occur much more frequently in iodine-deficient areas.

How is Thyroid problem diagnosed?

A Blood test called Thyroid Function Test is done to check the levels of hormones mainly :

Thyroid Stimulation Hormone ( TSH)
Thyroid Hormone Thyroxine (T4)
Thyroid Hormone triiodothyronine ( T3)

Thyroid and your developing baby:

For the first 10-12 weeks of pregnancy, the baby is completely dependent on the mother for the production of thyroid hormone. By the end of the first trimester, the baby’s thyroid begins to produce thyroid hormone on its own.

However, the mother still need to consume adequate amounts of iodine for the baby to produce the thyroid hormones. The World Health Organization recommends iodine intake of 200 micrograms/day during pregnancy to maintain adequate thyroid hormone production. In other words, Pregnant women need about 66 per cent more iodine than non-pregnant women. Iodine is very important during pregnancy as it supports baby’s growth and mental development. Some of the main sources of iodine are iodised salt, fish, cheese, milk, curd, egg etc.


This condition occurs when the thyroid gland produces inadequate amount of thyroid hormones. Some common causes of hypothyroidism include Iodine deficiency, an auto-immune disorder called Hashimoto’s thyroiditis , inadequate treatment of already known hypothyroidism etc. Some of the common symptoms are :

• Fatigue
• Poor concentration
• Dry skin
• Constipation
• Feeling cold
• Fluid retention
• Muscle and joint aches
• Depression
• weight gain
• muscle cramps
• loss of desire for sex etc


This condition occurs when the thyroid gland produces an excessive amount of thyroid hormones. The most common cause (80-85%) of hyperthyroidism during pregnancy is Graves’ disease, an auto-immune disorder. The diagnosis of hyperthyroidism can be somewhat difficult during pregnancy and a careful observation, history and lab tests are taken into consideration. Some of the common symptoms are:

• Mood swings, nervousness, hyperactivity
• Fast heart rate
• Fatigue, difficulty sleeping, muscle weakness
• Intolerance for heat
• Increase in bowel movements
• Increased sweating
• Concentration problems
• Unintentional weight loss
• increased appetite
• loss of interest in sex etc

Risk to mother and baby:

Hypothyroidism Risk :

Risk to mother: Untreated, or inadequately treated, hypothyroidism has been associated with maternal anemia, muscle pain and weakness, congestive heart failure, pre-eclampsia, placental abnormalities, low birth weight infants, and postpartum bleeding. These complications are more likely to occur in women with severe hypothyroidism.

Risk to baby: As Thyroid hormone is critical for brain development, babies born with congenital hypothyroidism (no thyroid function at birth) can have severe cognitive, neurological and developmental abnormalities if the condition is not recognized and treated promptly.

Hyperthyroidism Risk :

Risk to mother: Inadequately treated maternal hyperthyroidism can result in early labor and pre-eclampsia. Graves’ disease often improves during the third trimester of pregnancy and may worsen after childbirth.

Risk to baby: Uncontrolled hyperthyroidism during pregnancy can result in fetal tachycardia (fast heart rate), small for gestational age babies, prematurity, stillbirths and possibly congenital malformations etc.

Treatment Risk:

Hypothyroidism: Mainly through adequate replacement of thyroid hormone in the form of synthetic levothyroxine. Ideally, hypothyroid women should have their levothyroxine dose optimized prior to becoming pregnant. Women with known hypothyroidism should have their thyroid function tested as soon as pregnancy is detected and their dose adjusted by the doctor. Thyroid function tests should be checked approximately every 6-8 weeks during pregnancy to ensure that the woman has normal thyroid function throughout pregnancy

Hyperthyroidism: Mild hyperthyroidism is monitored closely without medication as long as both the mother and the baby are doing well. When hyperthyroidism is severe, anti-thyroid medications are the treatment of choice. Close monitoring of levels, with monthly testing is required throughout the pregnancy.

Remember- Thyroid problems should never be treated lightly as it can lead to severe complications both for the mother and the baby, especially if it is left untreated and unmonitored.


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