New Thyroid Guidelines Released for Pregnancy
data clarifying the risks of insufficient thyroid activity during pregnancy on
the health of the mother and fetus, and on the future intellectual development
of the child, have led to new clinical guidelines for diagnosing and managing
thyroid disease during this critical period. The guidelines, developed by an
American Thyroid Association (ATA) expert task force, are presented in Thyroid,
a peer-reviewed journal published by
Mary Ann Liebert, Inc. (2011)and are available free online.
Thyroid disease is present in 2-5 percent of all women and 1-2 percent of
women in the reproductive age group. Thyroid problems are common in women who
Several of the thyroid disorders which tend to occur during pregnancy are
autoimmune in nature. By this we mean that the body develops antibodies directed
against thyroid cells, which then affect the way the thyroid gland functions.
Antibodies which damage the thyroid cells may result in lymphocytic thyroiditis
(inflammation of the thyroid), also known as Hashimoto's disease. These
damaging antibodies can reduce the function of the thyroid and lead to
hypothyroidism. On the other hand, your body can make antibodies against
thyroid tissue which can stimulate thyroid cell function. In this case,
hyperthyroidism due to over-function of the thyroid (Graves' disease) may be
As you can see, thyroid conditions are a very common health problem, and have
great impact on pregnancies
and fertility. Not only is
thyroid disease related to
miscarriage, but subclinical hypothyroidism or positive thyroid antibodies
can impact the brain development of the
fetus and have been linked
to poor intellectual development in the baby. Hyperthyroidism is related to
miscarriage and a host of problems such as intrauterine growth restriction. So
this is an issue we must take seriously!
Among the many specific recommendations detailed in the guidelines are the
following: women with overt hypothyroidism or with subclinical hypothyroidism
who are TPO antibody positive should be treated with oral levothyroxine; use of
other thyroid preparations such as triiodothyronine or desiccated thyroid to
treat maternal hypothyroidism is strongly recommended against; and women with
subclinical hypothyroidism in pregnancy who are not initially treated should be
monitored for progression to overt hypothyroidism with serum TSH and free T4
measurements about every 4 weeks until 16-20 weeks gestation and at least once
between 26-32 weeks gestation.
The new clinical guidelines focus on several key areas in the diagnosis and
management of thyroid disease during pregnancy and postpartum: thyroid function
tests, hypothyroidism, thyrotoxicosis, iodine, thyroid antibodies and
miscarriage/preterm delivery, thyroid nodules and cancer, postpartum thyroiditis,
recommendations on screening for thyroid disease during pregnancy, and areas for
The new guidelines suggest the following:
Trimester specific tighter ranges for TSH:
First trimester normal range
0.1 to 2.5 mIU/L
0.2 to 3.0 mIU/L
0.3 to 3.0 mIU/L
Women who are already receiving thyroid replacement therapy should
increase their dose by 25% to 30% when they become pregnant.
The total amount of iodine should be 250 ug from all dietary and
Monitoring is important to ensure that women with hypothyroidism or
subclinical hypothyroidism are not at risk. TSH should be measured once
every 4 weeks until 16 to 20 weeks’ gestation and at least once between 26
and 32 weeks’ gestation.
According to the ATA Statement:
What Should You Do?
While the ATA and endocrinologists debate which research is necessary in the
bigger picture, women who are contemplating pregnancy have options to consider:
Pregnant mothers with overt or subclinical hypothyroidism are at an
increased risk for premature delivery.
Women who are contemplating pregnancy -- even those without a personal or
family history of thyroid or autoimmune disease -- should, as a precautionary
measure, get a basic TSH test. This can be done through your doctor, or in many
states, you can order your own tests.
Any woman who has a personal or family history of thyroid or autoimmune disease
-- should have her thyroid tested prior to becoming pregnant, and again within
the first weeks of early pregnancy. She should be tested throughout the pregnant
as often as symptoms might indicate, but at least once a trimester. The
offspring of mothers with thyroid hormone deficiency or thyroid stimulating
hormone elevation during pregnancy may be at risk of mild impairment in their
intellectual function and motor skills.
Any woman with a diagnosed thyroid condition should have her thyroid tested
prior to becoming pregnant, and again within the first several weeks of early
pregnancy. She should be tested frequently throughout the pregnancy, including
several times in the first trimester, and throughout the pregnancy as often as
clinical signs and symptoms might indicate, but at least once in each of the
second and third trimesters. Pregnant women being treated with thyroid hormone
replacement often require a 30-50% increase in their thyroid hormone dose.
Women contemplating pregnancy should make sure they start taking a prenatal
vitamin that includes not only folic acid, but iodine, before becoming pregnant,
and continue taking that vitamin throughout pregnancy. (Note, however, that
women taking a prenatal vitamin with iron will need to be careful about
separating the vitamins from their thyroid hormone by at least 3-4 hours at
minimum, or the iron may make the thyroid hormone less effective by interfering
The ATA called for more extensive research into the nature of these problems, as
well as the need for expanded testing programs.
Dated 22 August 2011