Mustansiriyah Journal of Pure and Applied Sciences

Review article Maternal hypothyroidism during pregnancy

Fadhel Mohammed Lafta

Ban Jasim Mohamad

Bassam K. Abdul Ameer

Fadhel Mohammed Lafta

DOI: https://doi.org/10.47831/mjpas.v3i1.111

Keywords: hypothyroidism, pregnancy, iodine

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Abstract

The thyroid gland in pregnant women undergoes significant structural and physiological changes.  One example is the universal enlargement of the gland in pregnant women in countries with sufficient and deficient body iodine levels.  In addition, an increase of 50% occurs in both the production of the thyroid hormones and the daily need for iodine. Such alterations also continuously occur in women in general, but the pathological reactions taking place during pregnancy may lead to various aspects of dysfunction of the glans, including hypothyroidism which is commonly observed in pregnant women who might be seriously affected, along with the developing fetus. The situation can become complicated with other physiological disorders, including gestational hypertension, premature delivery, and fetal growth restriction. About 3 to 5 % of pregnant women develop hypothyroidism, making it the main form of thyroid dysfunction in this group of women. As compared to the overt form, subclinical hypothyroidism occurs in a higher frequency. It is diagnosed when the level of the thyroid-stimulating hormone (TSH) in the serum is higher compared to the pregnancy-specific reference range. Hormone levels higher than 2·5 mIU/L in the 1^st trimester and 3 mIU/L in the 2^nd and 3^rd trimesters are also indicative of this condition. However, a number of studies reported serum TSH values of 5-10 and >10 mIU/L to diagnose subclinical and overt hypothyroidism, respectively. Close monitoring is especially important during the first trimester because untreated hypothyroidism during this time might lead to irreversible disorders in the nervous system of the developing fetus.