What is hypothyroidism during pregnancy?

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    Hypothyroidism and pregnancy: everything you need to know

    Hypothyroidism can affect many young women. What is the impact on their fertility? This pathology which results in a too high level of TSH which can impact the pregnancy and the fetus. What to do when you have hypothyroidism during pregnancy?

    In the vast majority of cases, thyroid conditions are autoimmune in nature : thyroid function is damaged by the mother's own antibodies. They attack thyroid cells and create an inflammation known as " Hashimoto's thyroiditis ". Less commonly, thyroid nodules or goiters are detected during pregnancy, which can be associated with hypothyroidism .

    Pregnancy and Thyroid Disorders: Can Pregnancy Affect Thyroid? 

    Hypothyroidism is when a person has a lack of thyroid hormone . This means that not enough thyroid hormones are being secreted by thethe thyroid . There are two types of thyroid hormones. Thyroid hormone T4 (also called thyroxine) and T3 are both secreted by the thyroid.

    How to get pregnant when you have hypothyroidism?

    There is no contraindication at all to getting pregnant for a woman with hypothyroidism provided that it is properly balanced . When a woman with this disease wants to get pregnant, doctors make sure that her hypothyroidism is well balanced if possible before the start of the pregnancy. To do this, the doctor will give a target TSH level to achieve.

    When patients have known hypothyroidism, they are already on replacement therapy. The doctor asks them to start the pregnancy with a TSH target of around 2.5. If the patient starts their pregnancy with a TSH level that is not perfectly within the targets, I always reassure the patients and adjust the treatment dosage as quickly as possible , from the first trimester of pregnancy .

    What TSH level can a woman with hypothyroidism have during pregnancy?

    TSH is the hormone test that determines whether a person has thyroid dysfunction  (hypothyroidism or hyperthyroidism ). When the thyroid is functioning normally, it is called euthyroidism. Euthyroidism is defined as a normal TSH level of between 0.5 and 4 depending on the laboratory. A person has hypothyroidism when the TSH level is higher than normal.

    Should you adjust your treatment during pregnancy if you are being treated with levothyroxine?

Yes, hypothyroidism treatment doses generally need to be adjusted when there is a desire to become pregnant or the woman is already pregnant.

    Pregnancy influences the function of almost all organs… and the thyroid is no exception! From the first trimester, pregnancy requires extra work from the thyroid gland. From the beginning of pregnancy, there are physiological changes responsible for an increase in thyroid hormone requirements of approximately 25 to 30% . Furthermore, and this is the most important point, until the 4th month of pregnancy , the fetus needs the mother's thyroid hormones for its brain development . In fact, the fetal thyroid is only functional from the 4th month of pregnancy.

    For these different reasons, it is necessary to increase the treatment dose by 25 to 30% from the beginning of pregnancy. This change in treatment does not present any danger for the child . 

    The proper balance of hypothyroidism is based on the dosage of TSH which should be carried out every six weeks and will allow the dose of thyroxine to be readjusted if necessary.

    Should I report pre-pregnancy thyroid problems to my doctor?

    Of course, yes! The thyroid plays a key role in a woman's pregnancy : it provides the fetus with the hormones necessary for its development. In the case of hypothyroidism, hormone production is insufficient and certain precautions must be taken.

    Proven hypothyroidism, a family history of hypothyroidism or even insignificant findings on thyroid function must be reported to the doctor monitoring the pregnancy .

    What are the symptoms of hypothyroidism during pregnancy?

    Early or mild hypothyroidism is most often asymptomatic or has very few symptoms. This is why diagnosis is difficult . This is called subclinical hypothyroidism.

     Hypothyroidism is biologically expressed by an increase in TSH . In the absence of symptoms , the diagnosis of subclinical hypothyroidism is based on an isolated increase in the TSH level. 

    On the other hand, when hypothyroidism becomes more significant, the pregnant woman may experience a certain number of symptoms, but they are not very specific:
  • unusual fatigue ;​
  • chilliness ;
  • weight gain that remains moderate ;
  • muscle pain ;
  • the appearance of a goiter (increase in the volume of the thyroid);
  • a slowing of the heart rate ;
  • concentration problems ;
  • drowsiness .​

    What are the steps to take when you are pregnant and have hypothyroidism?

    When hypothyroidism is discovered in a pregnant woman , the doctor (most often an endocrinologist) will assess the etiology of this hypothyroidism and quickly implement treatment with thyroid hormone.

    What treatment is given to a pregnant woman with hypothyroidism?

    Treatment for a pregnant woman with hypothyroidism is the same as for other patients suffering from this disease . This is called replacement therapy. Treatment for hypothyroidism consists of natural thyroid hormones , so there is no risk to the baby.

    The treatment of hypothyroidism consists of taking L-thyroxine tablets every day, which corresponds to T4. Why do we use T4 treatment? Because T4 is the hormone that is able to cross the placenta . The fetus will therefore be able to use this thyroid hormone for its brain development. The dosage of the treatment is adapted to the severity of the hypothyroidism. This is the only treatment that exists.

    Why is it sometimes necessary to combine iodine with the treatment of hypothyroidism in pregnant women?

    When the mother-to-be lives in an area of ​​iodine deficiency , it is possible to combine iodine with L Thyroxine treatment . Iodine deficiency areas correspond to regions poor in dietary iodine, the lack of iodine promoting hypothyroidism.

    Iodine is all the more important because it is the mother who must provide it to the fetus so that the child's thyroid hormones can be synthesized in sufficient quantities. This is why, as a precautionary measure, pregnant women are also advised to consume fish and iodized salt twice a week to maintain sufficient iodine levels. There are also pregnancy food supplements enriched with iodine.

    Is it serious to be pregnant with hypothyroidism?

    Today, hypothyroidism is easily detected in the first trimester of pregnancy by a blood test or a biological assay. "If the pregnant woman has mild hypothyroidism, there is little risk for the course of the pregnancy. A slightly higher risk of miscarriage has been noted," explains Dr. Isabelle Héron. The main risk of this disease during pregnancy is the fetal risk since the neurological development of the fetus is dependent on the mother's thyroid hormones until the 4th month of pregnancy.

    When hypothyroidism is diagnosed early in pregnancy, I quickly set up hormonal treatment and we always tell expectant mothers the importance of a well-balanced hormonal treatment with a TSH target of around 2 mIU/L.

    Is screening for hypothyroidism systematic in pregnant women?

    Screening for hypothyroidism in pregnant women is not systematic. Hypothyroidism is detected early in pregnancy based on risk factors. Risk factors may include: a family history of thyroid disease (people with hypothyroidism or hyperthyroidism), a history of goiter in the family, the existence of treatment that may impact thyroid function, patients themselves having a history of thyroid disease, whether hyperthyroidism or hypothyroidism, if they have undergone thyroid surgery, if they have a known thyroid nodule.

    What are the risks for the baby if the mother has hypothyroidism?

    Proper functioning of the thyroid gland is very important during pregnancy , especially in the first trimester. During pregnancy, the fetus needs thyroid hormones for its own development . During the first trimester of pregnancy, the fetus is completely dependent on the mother's hormones. The fetal thyroid is only functional from the 18th or 20th week of amenorrhea. Maternal thyroid hormones are particularly essential for the development of the fetus's nervous system . If the mother is hypothyroid and therefore does not secrete enough thyroid hormones, particularly T4, there may be an impact on the fetus.

    Although there is little risk to the fetus , the major risk to the baby when the mother has hypothyroidism and it is not treated or is treated late is intellectual disability . Several studies have shown a decrease in intellectual abilities in children born to mothers who had insufficiently balanced hypothyroidism.

    Regarding breastfeeding , it is not contraindicated if the young mother is treated with levothyroxine.

    Is screening for hypothyroidism in babies at birth systematic?

    Since 1975, hypothyroidism has been systematically screened in newborns . It is one of the pathologies that are screened for at birth. Neonatal screening is carried out by taking a few drops of blood by a simple heel prick on the 3rd day of life. This sample is necessary to perform the TSH measurement and immediately implement treatment if hypothyroidism is diagnosed.

    After giving birth, can a young mother develop hypothyroidism?

    A young mother may develop hypothyroidism a few weeks after giving birth . This postpartum hypothyroidism is often linked to autoimmune thyroiditis . That is to say, to the production of anti-thyroid antibodies, which is often significant after pregnancy.

    These hypothyroidisms are sometimes missed because fatigue is often not attributed to hypothyroidism, but is identified as a normal sign after pregnancy and restless nights. In the vast majority of cases, everything returns to normal before the end of the first year after pregnancy.

    Is screening for postpartum hypothyroidism systematic?

    There is no systematic screening for postpartum hypothyroidism . It may be screened if the patient has a family history or if the patient developed hypothyroidism during a previous pregnancy. However, screening may be done if the new mother develops certain symptoms . Here are the symptoms that may require screening for postpartum hypothyroidism:

  • if the young mother does not have a return of menstruation ;
  • if she is very tired ;
  • if she fails to lose weight ;
  • if she has mood disorders or suffers from postpartum depression. "In the case of postpartum depression, we systematically screen for hypothyroidism.

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