Thyroid problems during pregnancy: should you s'worry?

Thyroid problems during pregnancy: should you s'worry?

Thyroid problems, hypo- or hyperthyroidism, are the cause of various symptoms that can be very disabling in many ways. We explain.

What is the thyroid?

The thyroid is a 20-gram gland located at the base of the neck. Its shape is reminiscent of a butterfly, with a central part (isthmus), followed by right and left lobes.

Benefits for the body

The thyroid is one of the largest endocrine glands. Its role is to secrete thyroid hormones: thyroxine (T4) and triiodothyronine (T3). These hormones regulate metabolism, body temperature, heart rate, the digestive and nervous systems...

In short: the thyroid really is your body's conductor. The menstrual cycle is therefore influenced by the thyroid (mood, sexual desire...).

TSH levels

Thyroid hormones are produced by a pituitary hormone called TSH (Thyroid Stimulating Hormone).

What role does the thyroid play during pregnancy?

The pregnancy is a time of upheaval for the thyroid gland. In fact, during this period, the thyroid increases its activity as it has to produce even more hormones to ensure the growth and proper development of the fetus.

These thyroid hormones are produced by iodine. Pregnancy is a period when iodine deficiency is very frequent (part of it passes through the placenta to the foetus, while the rest is eliminated by the kidneys to an even greater extent in pregnant women).

This deficiency can lead to an enlargement of the thyroid gland, known as goiter. Fortunately, there are solutions to reverse this phenomenon.

What is the normal TSH level for pregnancy?

Defining TSH levels ensures that a person is not suffering from thyroid dysfunction. A thyroid that functions normally is called euthyroid. A normal TSH level is between 0.4 and 2.5 MUI/L during the first trimester of pregnancy. When it exceeds this threshold, we speak of hyperthyroidism. SIf it's too low, it's hypothyroidism.

What thyroid disorders should I watch out for during pregnancy?

During the first four months of pregnancy, the thyroid plays an extremely important role. In fact, it ensures the proper development of the fetal brain by supplying it with a sufficient quantity of hormones.

For this reason, thyroid activity in pregnant women is closely monitored. Regular monitoring will detect any disorders that could have harmful consequences for both mother and unborn child.


There are 3 types of hyperthyroidism in pregnant women.

Firstly, transient gestational thyroiditis, which affects 15% of pregnant women during their first trimester. It's a temporary condition, due to increased levels of BHCG in the body, which stimulates the thyroid (increasing T4) and reduces TSH.

Secondly, there is transient gestational hyperthyroidism, which is particularly noticeable in women who are pregnant with twins, or who suffer from gravid vomiting. But don't panic: in most cases, this thyroid condition disappears at the beginning of the 2nd trimester of pregnancy, and no special treatment is required unless you experience intense vomiting. In this case, treatment may be prescribed.

Graves' disease is the cause of the vast majority of hyperthyroid disorders. It may be responsible for the development of certain complications for both mother and child, such as :

  • Prematurity;
  • In utero growth retardation;
  • Fetal hypothyroidism: TSH receptor antibodies cross the placental barrier;
  • Pre-eclampsia;
  • Retroplacental hematoma.

Since the risks are present, it's very important to offer professional care.

Other types of hyperthyroidism are rare, but can occur as a result of a wide variety of pathologies. They must be ldiagnosed and treated separately.


An estimated 4% to 8% of women suffer from hypothyroidism. The disease has two origins:

  • Hashimoto's thyroiditis ;
  • Iodine deficiency;

Unlike hyperthyroidism, hypothyroidism is often difficult to detect in early pregnancy. This is because peripheral hormone levels (T4) drop. Hypothyroidism is closely monitored if the pregnant woman has risk factors or a medical history. Hypothyroidism can lead to complications such as :

  • Neurological development can be slowed, resulting in mental retardation in l;
  • Or fetal hypotrophy;

Hypothyroidism may also be associated with a risk of retroplacental hematoma, preeclampsia or fetal distress.

Hypothyroidism can lead to obstetrical risks (recurrent miscarriage, premature delivery, post-partum thyroiditis).

What are the symptoms of a thyroid problem?

There are several symptoms that can indicate a thyroid problem:

  • Rapid and significant weight loss;
  • Excessive sensitivity to heat;
  • Sudden thirst;
  • Hot flashes;
  • Excessive sweating;
  • Mood disorders l;
  • Pregnancy insomnia;
  • Hyperactivity;
  • Stress and anxiety;
  • Bulging eyes;
  • An increase in the volume of the neck, suggesting a goiter;
  • Increased frequency of bowel movements;
  • Pregnancy diarrhea;
  • Palpitations;
  • Fewer periods or even none at all.

When a patient presents symptoms suggestive of thyroid dysfunction, her doctor will prescribe a thyroid work-up. The aim of this test is to check TSH levels.

How to treat thyroid problems in pregnant women?

Radioactive iodine-based treatments are not recommended during pregnancy. However, other treatments are available to restore hormonal balance: synthetic antithyroid drugs and beta-blockers. These treatments require careful monitoring. Time off work and rest are recommended.

What are the risks of thyroid disease for pregnancy and the baby?

Thyroid disorders are easily detected during the first trimester of pregnancy. There are no particular risks to report, but the main risk is to the fetus, since the neurological development of the fetus is dependent on the mother's thyroid hormones until the 4th month of pregnancy.

For this reason, it's vital that the thyroid gland functions properly during pregnancy, especially in the first trimester when the fetus is developing on its mother's thyroid hormones. It's not until the 18th or 20th week of amenorrhea that the fetal thyroid becomes functional.

The risks are minimal, however, because as already mentioned, hypothyroidism is treated very quickly. If left untreated, or treated too late, the risk to the fetus is intellectual retardation.

Thyroid problems and fertility: is it possible to get pregnant?

Thyroid pathologies can in fact be linked to infertility, particularly in the case of hyperthyroidism (which affects 2.3% of women who have difficulty getting pregnant, and 1.5% of the general female population).

Women suffering from hyperthyroidism are more sensitive to GnRh (the hormone that releases pituitary gonadotropin). This leads to greater production of luteinizing hormone (LH), which increases estrogen levels. This can lead to menstrual cycle disorders such as polymenorrhea (when the frequency of periods increases), making natural pregnancy more difficult. Despite this, women with hyperthyroidism still ovulate.

Hypothyroidism can also be a source of female infertility. The main cause of these difficulties in conceiving is high TSH levels, which can lead to oligomenorrhea (i.e. reduced size and frequency of periods), amenorrhea or anovulatory cycles. It also reduces the chances of successful pregnancy in MAP procedures.


Thyroid and pregnancy FAQs

Does TSH increase during pregnancy?

During pregnancy, TSH levels generally drop during the first few months. This is a natural process of the thyroid glands, and does not mean that the mother is suffering from hyperthyroidism. Thereafter, TSH rises and returns to normal.

Can levothyrox be taken during pregnancy?

Levothyrox (synthetic T4, synthetic form of the hormone thyroxine) is safe for the fetus. We invite you to consult your doctor if you have any questions about treatments that may or may not be recommended during pregnancy. In any case, this medication is not available without a prescription.

More articles

Back to blog

Leave a comment

Please note that comments must be approved before being published.

Our best sellers

1 from 8

The information contained in the articles on is general information only. Although reviewed by health professionals, this information is not error-free, does not constitute health advice or consultation, and is not intended to provide a diagnosis or suggest a course of treatment. Under no circumstances may this information be used as a substitute for medical advice or consultation with a healthcare professional. If you have any questions, please consult your doctor.