Hypothyroidism in pregnancy
definition
About 2.5% of pregnant women have an underactive thyroid (Hypothyroidism) affected.
This means that the thyroid gland does not produce enough thyroid hormones (T3, T4).
Hypothyroidism can either have already occurred before pregnancy or it can only develop due to the increased demands during pregnancy.
Since an undersupply of maternal thyroid hormones harbors many risks for the unborn child, it should be diagnosed as early as possible and treated accordingly.
However, hypothyroidism during pregnancy can be treated well and then has no negative effects on the child.
Also read our main page on: Hypothyroidism
causes
In hypothyroidism, the thyroid gland produces fewer hormones than the body needs for mother and child during pregnancy. This undersupply slows down the metabolism and as a result the unborn child can suffer from mental and physical deficits.
There are several causes of an underactive thyroid during pregnancy. The hypothyroidism can either have existed before the pregnancy or develop during this time.
During pregnancy, the need for thyroid hormones increases by around 50%, as the baby has to be looked after by the mother.
A healthy thyroid can easily compensate for this increased requirement, whereas hypothyroid pregnant women cannot meet the requirement and need a substitution of thyroid hormones. An underactive function that only develops during pregnancy can regress completely after the birth.
Pre-existing hypothyroidism is often caused by chronic inflammation of the thyroid gland (Hashimoto's thyroiditis), which is triggered by the body's own immune system. An underactive thyroid can also be induced by medication or after an overdose of Anti-thyroid drugsthat inhibit thyroid function develop.
In some cases, hypothyroidism is caused by benign or malignant growths (Tumors) in the thyroid gland. After surgical removal of the thyroid gland after a carcinoma, there is also a deficiency in thyroid hormones.
Under-function due to iodine deficiency is rather rare in our part of the world, as iodine is added to the table salt as a precaution.
diagnosis
An underactive thyroid during pregnancy can be clearly diagnosed by the doctor using a blood count with hormone determination.
The size of the thyroid gland can be determined by scanning and ultrasound diagnostics, but an assessment of the function is only possible on the basis of the blood values.
If the thyroid is underactive, the TSH levels are increased, whereas the amount of free thyroxine (T4) in the blood is decreased. If hypothyroidism has been diagnosed, substitution with thyroid hormones and regular blood tests during pregnancy are urgently required to prevent damage to the fetus.
Read more about this at: Hypothyroidism values
Concomitant symptoms
An underactive thyroid during pregnancy manifests itself in uncharacteristic symptoms such as
- general tiredness and fatigue,
- Feeling weak,
- constipation
- and unexplained weight gain.
It can also:
- increased feeling of cold,
- Hair loss
- and dry skin come,
- occasionally depressive moods are also reported.
However, none of these symptoms are specific and do not necessarily have to occur.
In addition, an underactive thyroid is difficult to recognize based on the symptoms, because the symptoms can vary in severity and some symptoms are simply caused by the pregnancy itself.
A precise evaluation of the thyroid function can only be carried out by a doctor using the hormone level in the blood.
Weight gain
Unexplained weight gain can be a symptom of impaired thyroid function. However, it is difficult to attribute weight gain during pregnancy to hypothyroidism, since every pregnant woman inevitably gains weight.
When the thyroid can no longer produce sufficient amounts of hormones, the metabolism slows down. This is because the energy consumption is lower.
The thyroid hormones T3 and T4 play a central role in the human metabolism and influence the energy balance, growth and function of individual organs.
If the same amount of energy is consumed in the form of food as before the illness, with a reduced energy expenditure, this leads to an excess of energy in the body. This excess energy cannot be used up and is stored in the body as fat, which leads to weight gain.
The amount of weight gain in the context of an underactive thyroid depends on a number of factors, such as general eating habits and the amount of physical activity the patient engages in.
Please also read: Weight gain during pregnancy
nausea
An underactive thyroid can also affect the gastrointestinal tract. In addition to constipation and a feeling of fullness, nausea can also increase.
Many pregnant women already suffer from nausea and vomiting in the first few weeks of pregnancy, which is why it is difficult to attribute increased nausea to an underactive thyroid.
Please also read: Nausea in pregnancy
treatment
In order to compensate for the low hormone level in hypothyroidism, the pregnant woman is given thyroid hormones in the form of tablets.
This treatment is also considered safe during pregnancy and has no negative effects on the unborn child.
With hormone substitution, the thyroid hormone levothyroxine (Euthyrox®) is administered. This is an active ingredient that corresponds to natural thyorxine (T4) and supplies the growing fetus with the necessary hormones.
If the drug is administered in the correct dosage, there are no side effects. The pregnancy progression of women suffering from hypothyroidism and taking the tablets is good.
The intake of thyroid hormones during pregnancy should only be done as directed by a doctor. In addition, the thyroid gland and blood values must be checked regularly during pregnancy to ensure that they are optimally adjusted.
How bad is it if I forget the tablets?
Depending on the severity of the hypofunction and the corresponding dose of tablets to be taken, irregular intake or premature discontinuation of the medication can lead to developmental disorders in the child.
If you forget to take the medication once, this usually has no serious consequences.
It is recommended that you continue taking it in the normal rhythm and not take the missed dose in addition.
What are the consequences of underactive pregnancy?
The need for thyroid hormones increases during pregnancy as both the mother and the child need to be supplied with them. Maternal hypothyroidism can be balanced out with appropriately dosed thyroid hormones. These drugs should be taken regularly during pregnancy and the function of the thyroid gland should be closely monitored by the doctor. If the medication is forgotten several times or discontinued early against medical advice, this can have drastic consequences for the unborn child.
The insufficient supply of thyroid hormones to the fetus can lead to mental retardation and physical malformations. It also increases the risk of spontaneous miscarriage or premature birth.
The risk that the placenta will detach prematurely and thereby damage the child is increased.
Hypothyroidism in pregnant women is also untreated
- a low birth weight,
- an increased risk of preeclampsia (pregnancy poisoning)
- and increased maternal mortality during childbirth.
Can an underactive thyroid cause my baby to malform?
If the underactive thyroid in the mother is recognized early and treated accordingly, there is no risk of malformation in the baby.
However, if hypothyroidism is untreated, it can impair the mental development of the unborn child. Studies show that children of untreated hypothyroid mothers of school age have a significantly reduced intelligence quotient (IQ) compared to other children.
In addition, a significantly higher rate of premature births (births before the 34th week of pregnancy) was found in women with untreated hypothyroidism. The organs of premature babies are not yet fully developed and there is accordingly a risk that the children will be physically and mentally impaired.
Read more about this at: Premature birth
Usually the mother produces thyroid hormones, which are essential for fetal development. The fetus can only produce thyroid hormones from the 20th week and is dependent on maternal care before that.
But women with an underactive thyroid can also lead a normal pregnancy and give birth to healthy children. For this it is important to determine the disease as early as possible, to treat it accordingly and to have the function of the thyroid gland regularly checked by the doctor.
Which drugs can be used?
To treat hypothyroidism during pregnancy, L-thyroxine (Euthyrox®) is used as the drug of choice. This thyroid drug corresponds to the natural thyroxine (T4) and is taken in the form of tablets or capsules.
With the correct dosage there is no danger to the fetus.
It should only be taken after consulting a doctor and under his control.
What are the risks of an underactive thyroid for my baby during pregnancy?
If the thyroid is underactive during pregnancy, there is an increased risk of miscarriage, premature birth and stillbirth. The fact that the fetus does not receive enough maternal thyroid hormones via the placenta can impair mental and physical development.
However, if the maternal thyroid function is well adjusted, there is no risk of these risks occurring through drug substitution with the appropriate dose of thyroid hormones.
From which values (T3, T4, TSH) does it become dangerous for my baby?
An underactive thyroid is diagnosed based on changes in the level of hormones in the blood. The control hormone TSH is produced in the brain and leads to the release of T3 (triiodothyronine) and T4 (thyroxine) from the thyroid gland into the maternal bloodstream. From there, the thyroid hormones are transported to the baby via the placenta, where they help regulate fetal development.
A distinction is made between latent and manifest hypothyroidism. In the latent hypothyroidism If the concentrations of the free hormones T3 and T4 are still in the normal range, only the TSH value is increased. The body first tries to compensate for the hypothyroidism itself by the pituitary gland producing more TSH, which leads to the release of T3 and T4.
In the further course of the disease, the body can no longer compensate for the underfunction at some point and it comes to manifest hypothyroidism. The TSH values are still increased, but the concentration of free T3 and T4 in the serum is also decreased. The falling level of thyroid hormones threatens the fetus with developmental damage and the risk of premature birth increases.
The reference ranges in which the concentration of thyroid hormones should be in pregnant women depend on the trimester and cannot be determined in a binding manner. The following values can be used for orientation:
- in the 1st trimester (third of pregnancy) the TSH value should be between 0.1 and 2.5 mU / l,
- in the 2nd trimester at 0.2 - 3 mU / l
- in the 3rd trimester at 0.3-3mU / l.
If the concentration of TSH rises above these values, the free T3 and T4 should also be determined in any case.
A clarification and precise interpretation of the blood values should always be carried out by the gynecologist. Hormone substitution occurs in both latent and overt hypothyroidism.
Please also read: Thyroid levels in pregnancy
Does the underactive thyroid increase the risk of a miscarriage?
If hypothyroidism is left untreated during pregnancy, there is an increased risk of premature or stillbirth. The risk of miscarriage is particularly high in the first few weeks of pregnancy. This applies to both latent and manifest hypothyroidism.
