Thyroid disturbances can increase risk of miscarriage in women, say fertility experts

A woman on Reddit described two consecutive miscarriages within a gap of four years – clinical results showed her levels of thyroid hormones were borderline low. Initially she thought the pregnancy caused the hormones to fluctuate but later found out that she had an undiagnosed thyroid problem which kept hampering her pregnancies.

Clinical studies have found a direct correlation between disrupted thyroid hormones and complications with a pregnancy.

As per research, even minimal fluctuations in the levels of thyroid hormones can increase the risk of miscarriage or fetal death.

Experts say a pregnancy directly affects the functioning of the thyroid gland because of the increased metabolic demand both by the mother and the fetus’ body.

All about thyroid

Thyroid is a small, highly wrapped, butterfly-like gland that sits right at the back of your neck under the skin.

The gland releases hormones that are necessary to support the body's metabolism.

Among the two important secretions are - thyroxine (T4) and triiodothyronine (T3).

As per the Cleveland Clinic, this combination is collectively called the thyroid hormone because the T4 form of hormone is usually inactive and converted to T3 by most organs.

These hormones are the housekeepers of the body and help regulate — body temperature, metabolic rate, heart rate, pace of digestion and even brain health.

The demand for the hormone increases when a person is pregnant with a child, making it an irreplaceable need during this time.

Thyroid hormone in pregnancy

Both thyroid dysfunction and autoimmune diseases with the thyroid gland are prevalent among women in reproductive ages.

This is why fertility experts encourage expectant parents to test thyroid hormone levels in different stages of the pregnancy -before, during and after the pregnancy.

As per a study in the National Library of Medicine, there are bodily changes in the immunity of an expectant parent so that their body doesn’t turn against the fetus. This can sometimes trigger or activate underlying thyroid problems such as thyroid autoimmunity.

When the immune system of the parent starts to attack the thyroid, this can disrupt the hormone production which is vital for both the mother and the child.

As per Healthline, people having an underactive thyroid are often put on supplements during the pregnancy and those who are already on them are made to increase their dosage by 20 or 30 percent.

Speaking to DH, Dr. Lavanya R, a fertility specialist at Nova IVF Fertility (Sarjapur) said: “For many women, if the thyroid problem goes untreated it may lead to irregular cycles, weaker oocytes, implantation issues and a higher chance of miscarriage. In a few situations , women end up going through several fertility attempts without realizing that an underlying thyroid condition is quietly shaping their chances of conception outcomes.”

Thyroid hormones also significantly shape the nervous system of the fetus. In case of an underactive thyroid gland, it can cause long term developmental problems with the baby.

“Thyroid hormones play a key role in the development of the fetal brain and nervous system, especially in the first trimester, when the baby is really relying fully on the mother’s thyroid function. Also, even if the thyroid-stimulating hormone (TSH) levels are only mildly off, borderline abnormalities can still affect the pregnancy results,” said Dr. Lavanya R.

To test the levels of thyroid hormones in the body, a physician would often recommend some blood tests to evaluate TSH (Thyroid stimulating hormone), thyroxine (T4) and T3 (Triiodothyronine).

If the clinician suspects that the immune cells might be attacking the thyroid, they may ask the patient to undertake tests for some specific proteins to rule out autoimmune conditions like Hashimoto's disease and Graves disease.  

As per the American Thyroid Association, TSH levels are usually measured in milli-international units per liter (mIU/L). Levels higher than 4.5 mIU/L are associated with an increased risk for miscarriage and other pregnancy complications.