Thyroid dysfunction in pregnancy
Introduction
Maternal thyroid state is an important predictor of pregnancy outcome. Both hyperthyroidism and hypothyroidism have been shown to have an adverse impact on pregnancy. There is a wide range in the prevalence of thyroid dysfunction worldwide. In the USA which is considered an iodine
replete country, 2%–3% of apparently healthy, non pregnant women of childbearing age have an elevated serum TSH with the majority in the subclinical range. In southern Iran, the prevalence of hypothyroidism among pregnant women was shown to be 13.7%. In a study carried in India, the prevalence of thyroid dysfunction was high with subclinical hypothyroidism found in 6.47% and overt hypothyroidism found in 4.58% of pregnant women4. Hyperthyroidism is less commonly encountered in pregnancy with a prevalence of 0.2- 0.6%.
There is lack of data on the magnitude and different forms of thyroid dysfunction among pregnant women of Sri Lanka. Few studies have looked at the prevalence of iodine deficiency and autoimmune thyroid disease which are the two leading causes of hypothyroidism in pregnancy.In a cross sectional, nationally representative sample of pregnant women in Sri Lanka, median urinary iodine level was 113.7μg/l, which was far below the WHO recommendation of a level between 150 and 249 μg/l, indicating inadequate iodine status
of pregnant women in Sri Lanka. A study looking at the prevalence of thyroid autoantibodies in schoolgirls of Sri Lanka a decade ago, found the prevalence of thyroglobulin autoantibody (TgAb) to be markedly raised at 14.3% in 11 year olds and 69.7% among 16 year old girls.
Thyroid autoantibodies are known to be associated with thyroid dysfunction, mainly hypothyroidism.These observations raise the possibility of a high prevalence of thyroid dysfunction among pregnant women of Sri Lanka, which needs to be confirmed by studies.