More Problems with Hypothyroidism in Pregnancy
In the last issue of The Bridge in 1999, Dr. David Cooper
reported on a study appearing in the New England Journal of
Medicine dealing with the relationship between the mother’s
thyroid function and the baby’s long-term intellectual development.
The children born to mothers with hypothyroidism did less well on
a variety of intelligence tests, and had an average IQ that was
7 points lower.
Now a new study goes further in validating concerns about hypothyroidism
during pregnancy, this time showing the increased risk of miscarriage
in the second trimester.
This new study appeared November 2000 in the Journal of Medical
Screening, published quarterly by the British Medical Journal.
The study was conducted by Dr. Walter Allan, M.D., Director of Clinical
Services at the Foundation for Blood Research in Scarborough, Maine.
It involved more than 9000 women who were tested for low thyroid
function and were pregnant.
The study found that the miscarriage rate, or fetal death rate,
was 3.8% higher when the women’s TSH showed signs of hypothyroidism
(above 6mU/L) than in women with normal TSH (below 6mU/L). The risk
increased as the TSH levels rose in women with TSH levels above
10 mU/L carried a miscarriage rate of 8.1%. Six of every 100 miscarriages
in the study could be attributed to thyroid deficiency.
“Because little is known about the cause of late miscarriages,
our findings offer a new opportunity to possibly prevent some of
these,” said Dr. Allan. Further research may show that early
detection and treatment for maternal hypothyroidism is the key to
preventing these miscarriages.
Dr. Allan continued, “Our current study indicates that a
change in pregnancy screening practices may be warranted. Perhaps
expectant mothers should get a TSH test before pregnancy or as part
of the initial standard prenatal blood work.”
“Until more information becomes available, we at TFA agree
that TSH screening should be carried out in all women as soon as
the diagnosis of pregnancy is made,” says Dr. Lawrence Wood,
Medical Director of TFA. “The findings of Dr. Haddow and Dr.
Allan and their colleagues justify such testing. It is also reasonable
to consider such screening before pregnancy in any woman with a
personal or family history of thyroid dysfunction or a related immune
disorder such as juvenile (Type I) diabetes mellitus.”