Thyroid and Pregnancy

hyroid disease in pregnancy comprises conditions that affect both the mother and the fetus with potential important consequences for child development. 1 To inform the debate concerning the importance of thyroid disorders in pregnancy and the role of screening for thyroid function, it should be noted that the ges-tational incidence of hyperthyroidism is 0.2-0.3%, hypothyroidism 2.5% and thyroid anti-body (mainly TPOAb) positivity around 10%. 2 Pregnancy has marked effects on thyroid physiology and autoimmune thyroid disease tends to ameliorate through gestation due to general immunosuppression seen in pregnancy. The presence of thyroid antibod-ies is associated with infertility and miscarriage. 3 The explanation for these findings is unknown and, unfortunately, thyroxine treatment in the euthyroid woman does not increase pregnancy rates. 4 Transient gestational hyperthyroidism due to elevation in HCG – a weak thyroid stimu-lator-is common and presents as hypereme-sis gravidarum. 5 It more frequent in multiple pregnancies and in hydatidiform mole but normally does not require therapy. Around 5% of women require hospitalisation because of ketosis and dehydration. They have an increased incidence of high thyroid hormone levels and suppressed TSH. The TSH receptor antibody should be measured if there is diagnostic confusion between hyperemesis and Graves' disease. As mentioned, hyperthyroidism in pregnancy usually due to Graves' disease-is not common; untreated or poorly managed disease may result in miscarriage, pre term delivery, hypertension and pre eclampsia in the mother and intra uterine growth retardation and even increased death rate in the fetus. In a compliant patient, a good outcome can be expected both for mother and child if treatment with anti-thyroid drugs (propyl-thiouracil is preferred because of the association of methimazole with aplasia cutis and methimazole embryopathy) is instituted. 6 TSH receptor antibody should be measured at 36 weeks in such patients in order to predict the possibility of neonatal hyperthyroid-ism. Available evidence suggests that there is no significant effect of antithyroid drugs in utero on the long-term health of the neonate or child 7 even if the dose during gestation has caused iatrogenic fetal hypothyroidism. 8 Ra-dioiodine therapy is contraindicated in pregnancy but thyroid surgery may be performed safely in the 2nd trimester.