With stillbirths and preterm births affecting a significant number of pregnancies, new research looks into reducing the complications of childbirth for women with mild hypothyroidism.

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Common hormone replacement levothyroxine might reduce the risk of childbirth complications.

Stillbirth affects about 1 percent of all pregnancies, according to the Centers for Disease Control and Prevention (CDC).

The CDC report that 24,000 babies are stillborn in the United States each year. This is ten times more deaths than those caused by sudden infant death syndrome.

Preterm births also affect a large number of pregnancies in the U.S. The CDC report that 1 in 10 babies born in the U.S. in 2014 were the result of premature births, with preterm birth being the leading contributing factor to infant death.

The thyroid is an endocrine gland at the base of our neck. It is responsible for taking iodine from food and converting it into thyroid hormones. Once formed, these hormones are released into the bloodstream and transported throughout the body, where they control the body’s metabolism by turning oxygen and calories into energy.

In pregnancy, thyroid hormones are also crucial for developing the brain of the fetus. However, babies cannot produce their own thyroid hormones and are therefore completely reliant on their mother’s.

Mild hypothyroidism affects 2-3 percent of pregnant women. In hypothyroidism, the thyroid gland does not produce enough hormones.

With this in mind, researchers from the University of Cardiff in the United Kingdom hypothesized that mild hypothyroidism in mothers might affect a baby’s weight and overall well-being.

For their study, the researchers examined the effect a medicine commonly used to treat hypothyroidism might have on pregnant women.

The team – led by Dr. Peter Taylor – combined data from a thyroid screening study and linked it to pre-existing clinical data, in an effort to see whether correcting a mildly dysfunctional thyroid would benefit the mother and the fetus.

Overall, the study analyzed over 13,000 women who were 12-16 weeks pregnant. Of these, 518 had mild hypothyroidism.

Of the 518 women, 263 received treatment with the hormone replacement levothyroxine, while the remaining 255 women received no treatment at all.

The outcomes of administering levothyroxine were assessed by measuring stillbirth and preterm delivery rates, how long they were hospitalized for, the weight of the baby at birth, as well as the number of early cesarean sections.

The study is being presented today at the Society for Endocrinology annual conference in the U.K.

The team found that women with mild hypothyroidism indeed benefitted from levothyroxine treatment.

Women with mild hypothyroidism who had been treated with levothyroxine were less likely to give birth to low-weight babies, the researchers report. They were also less likely to have an early cesarean.

By contrast, women with mild hypothyroidism who did not receive any levothyroxine were more likely to have a stillbirth than women with normal thyroid function;

The group treated with levothyroxine experienced no stillbirths.

No other links were established between hypothyroidism treatment and obstetric outcomes.

Given the large number of complications associated with premature births, research into reducing the number of preterm births may be particularly useful.

According to the CDC, the sooner the baby is born, the higher is the risk of disabilities, or even death. Common complications for the baby include breathing and feeding problems, developmental delay, visual and hearing impairment, and cerebral palsy.

Although further tests are needed to confirm the results of this new study, the lead author emphasizes the practical advantages of potentially using thyroid medication early in the pregnancy.

Our work raises the possibility of providing real benefits from using a safe, cheap and well-established treatment by simply extending it to the number of pregnant women we treat. We should consider universal thyroid screening in pregnancy as it compares favorably in terms of cost-effectiveness with other conditions that we currently screen for.”

Dr. Peter Taylor

Learn how women with hearing loss might be at greater risk of preterm and low-birth-weight babies.