Thyroid diseases in pregnancy.

PURPOSE OF REVIEW: Thyroid disorders are common in pregnancy and affect maternal and fetal outcome.

RECENT FINDINGS: The reference values for normal thyroid function during first and second trimester had been re-evaluated recently. Hypothyroxinemia affects the neuropsychological development of the child. Maternal thyroid dysfunction or only the presence of thyroid-specific antibodies is associated with increased risk for early abortion, preterm delivery and neonatal morbidity. Pregnant women under levothyroxine treatment are often undertreated or overtreated. Screening for thyroid dysfunction of pregnant women is recommended and cost-effective.

SUMMARY: Recently, the recommended dose for iodine intake during pregnancy had been increased from 200 to 250 microg/day, because recent studies revealed that even mild-to-moderate iodine intake might affect the neuropsychological development of the child. About 5-18% of all pregnant women exhibit elevated thyroid-specific antibodies, but only 0.3% develop overt hypothyroidism and 0.1-0.4% overt hyperthyroidism. However, those pregnant women with autoimmune thyroiditis and normal thyroid function may have a restricted thyroid reserve, followed by hypothyroxinemia and/or thyroid-stimulating hormone increase during pregnancy. The incidence of miscarriage, preterm delivery and small for date offspring might be increased and probably a delayed neuropsychological development. Routine thyroid function testing at least as early as possible in all pregnant women is emphasized.