During pregnancy a woman's thyroid hormones take on newfound importance. For the first 10-12 weeks of gestation, the developing baby depends solely on its mother's production of thyroid hormone to meet its developmental needs.
After that the baby will begin to produce thyroid hormone on its own, but still depends on the mother's adequate dietary intake of iodine in order to make thyroid hormones.
If a woman is suffering from hypothyroidism, of which Hashimoto's disease is the most common cause, even at a subclinical level, her baby could be seriously affected. Further, because many of the symptoms of hypothyroidism -- fatigue, weight gain, constipation -- mimic those of pregnancy, the condition can be incredibly easy to miss.
Health Risks to Baby from Mom's Hypothyroidism
If your body is not producing enough thyroid hormone during pregnancy both your health and your newborn's could be at risk.
When left untreated, hypothyroidism can lead to preeclampsia -- a potentially serious condition involving high blood pressure -- placental abnormalities, low birth weight infants, stillbirth, miscarriage, anemia, and postpartum hemorrhage (bleeding).
In the baby, thyroid hormone is essential for normal brain and nervous system development, so low-functioning thyroid in the mother may lead to cognitive and developmental disabilities in the newborn. Even mild subclinical hypothyroidism during pregnancy may lead to subtle brain abnormalities in the child.
For instance, research published in the New England Journal of Medicine revealed that children born to women who had untreated hypothyroidism during pregnancy were nearly four times as likely to have lower IQ scores, and also were significantly more likely to have problems with attention, language and reading.[1]
Because the effects may be most severe when hypothyroidism is left untreated during the first trimester... a time when many women may not even realize they are pregnant yet... it's often important to get your thyroid checked prior to pregnancy.
Thyroid Screening for Pregnant Women Remains Controversial
A debate is raging over whether or not thyroid screening should be a routine part of pregnancy care. As it stands, pregnant women are NOT routinely screened, as the potential health benefits have been deemed inconsequential in relation to the costs of testing millions of pregnant women each year.
The exception is those at high risk of thyroid disease. Women with the following thyroid risk factors WILL be routinely tested for thyroid problems during pregnancy:
- Family or personal history of thyroid disease
- Goiter
- Symptoms of thyroid disease, including anemia or high cholesterol
- Type 1 diabetes or other autoimmune disorders
- Have received radiation to the head or neck as part of a medical treatment
- History of miscarriage or premature delivery
- Infertility
The concern is, however, that since many women may be suffering from hypothyroidism on a subclinical level, they may miss out on being screened and never know they have the condition.
In fact, a new study in the journal Clinical Thyroidology revealed that over half (55 percent) of pregnant women with Hashimoto's disease would be missed if only high-risk criteria like those listed above were examined.[2]
Another concerning issue has to do with thyroid antibodies. It's recommended that pregnant women be tested for thyroid problems if they test positive for thyroid antibodies, as this can be a sign of impending thyroid problems.
Research suggests that 3 percent to 20 percent of women have circulating thyroid antibodies during or shortly after pregnancy, and this increases the risk of becoming hypothyroid during pregnancy. However, thyroid antibodies are not normally a part of routine testing for pregnant women.
What Should You do if You're Pregnant or Thinking of Becoming Pregnant?
First, be aware of the signs and symptoms that you may have low-functioning thyroid:
- Fatigue
- Unexplained weight gain
- Cold intolerance
- Dry skin
- Joint and muscle pain and stiffness
- Muscle weakness
- Constipation
- Thinning hair
- Heavy or prolonged menstrual periods and impaired fertility
- Depression
- Slowed heart rate
If you notice any of these symptoms, insist that your health care practitioner check your thyroid function, ideally before you become pregnant.
However, it's very possible to have subclinical hypothyroidism and not experience (or notice) any symptoms at all. In fact, it's estimated that about 13 million Americans have hypothyroidism but have never been diagnosed. You could be in this group even if you've had your thyroid levels tested, as conventional lab tests to diagnose the disease can be misleading, labeling thyroid hormones as within the normal range when a problem still exists.
So if you suspect that you may have a thyroid problem, find a knowledgeable health care practitioner in your area who will work with you to determine if a problem is present. This is of crucial importance if you are pregnant or planning to become pregnant, as your baby's healthy development during the first trimester of pregnancy depends on your healthy thyroid function.
Keep in mind, too, that pregnancy places an increased demand on your thyroid gland. Because of this, if you are currently being treated for hypothyroidism you may need to adjust your treatment plan to account for this extra demand. Again, it is imperative that you work with a practitioner who understands the complexities of thyroid function, including during pregnancy, for your health and the health of your baby.
References
1. New England Journal of Medicine 1999 Aug 19;341(8):549-55.
2. Clinical Thyroidology Volume 22 Issue 11 November 2010 "Over half (55%) of the pregnant women with clear abnormalities suggestive of autoimmune thyroiditis with or without thyroid insufficiency would be missed if only the high-risk criteria are examined."
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