Thyroid Dysfunction in pregnancy

Thyroid dysfunction is commonly encountered in Pregnancy, esp Low thyroid function, commonly known as hypothyroidism. During the first half of pregnancy the baby is entirely dependent on the mother’s thyroid hormone.

Even borderline thyroid dysfunction is associated with adverse pregnancy outcomes.  Lack of thyroid hormones can cause, lower IQ in the offspring, verbal delay, autism, attention-deficit/hyperactivity disorder. In case of the mother it can cause, fetal loss, pre-term delivery, low birth weight, Pre-eclamsia.

Pregnancy causes additional demand on the thyroid axis of the mother, therefore those with adequate thyroid hormones prior to pregnancy, might fail to meet the increasing demand. Therefore, it is now advised for universal thyroid screening in pregnancy. Those already on thyroid hormone replacement should have their dose increased by 30% on confirmation of pregnancy.

There is 21% increased risk of pregnancy induced hypertension (PIH), in patients with sub-optimaly treated hypothyroidism. The further risks can be due to PIH, i.e Intra-uterine growth retardation, pre-term delivery. The pregnancy hormone hCG, (human chorionic gonadotropin) also interferes with the thyroid hormone axis and its interpretation.  Thyroid Autoimmunity, i.e. presence of anti thyroid antibodies, TPOAb, may be present in 10% otherwise normal women, with normal thyroid function , but is a risk factor for thyroid dysfunction during and post pregnancy.

Overactive thyroid, or Hyperthyroidism, though less common, has similar adverse pregnancy outcomes. Excessive vomitings, or hyperemesis gravidarum is commonly associated with hyperthyroidism. Anti-thyroid drugs are usually not recommended for gestational thyrotoxicosis due to their adverse effects on the baby.

If you have pre-existing thyroid dysfunction, or a positive family history of thyroid disease and you have a confirmed pregnancy or planning pregnancy, you must get your thyroid hormones checked and consult your endocrinologist and gynecologist for timely intervention to have a healthy pregnancy outcome.