Monitoring Foetus and Neonatal Outcomes in Patients With Current or Previous History of Hyperthyroidism

Aim: Graves’ hyperthyroidism can be associated with persistent TSH-receptor antibody (TRAB) and need for anti-thyroid drugs (ATD) during pregnancy warranting careful monitoring during pregnancy and the neonatal period. The aim of this retrospective observational study was to assess the outcomes of babies born of women with current or previous history of hyperthyroidism. Method: All women with previous or current hyperthyroidism were reviewed in the joint antenatal-endocrine clinic. Neonatal alert was instituted for all patients with positive TRAB at 20 weeks and/or requiring ATD into third trimester and included serial growth scans in third trimester, fetal medicine(FM) scan, review of neonate by paediatrician, thyroid function test(TFT) for the neonate on day 2(D2) and further tests as needed. Results: Of the 56 patients treated over a 2 year period, 31 qualified for this study. Thyroid statuses of patients were: active hyperthyroidism at conception=20; Post radioactive iodine (RAI)=4; post thyroidectomy =2; hyperthyroidism in remission prenatally=5. 24 patients were TRAB positive at 20 weeks (Strongly positive(>3xnormal) =10) & 7 were TRAB negative. 16 patients required ATD into 3rd trimester, of whom 11 required until delivery. Presence of any TRAB positivity did not statistically predict continuation or withdrawal of treatment. FM scan was normal in all patients (one patient had hydronephrosis which was deemed not related to thyroid status and resolved spontaneously after birth). Growth Scans were normal in 26 patients. One patient had a large for gestational age fetus which was not related to thyroid status (patient in Graves’ remission, TRAB weakly positive, normal FM scan, normal D2 and D14 TSH in the neonate). 4 patients had small for gestational age fetuses -2 had weakly positive and 1 strongly positive TRAB; all had normal FM scans; 1 neonate had high TSH at D2 and others normal; all neonates had normal TFT at D14. None of the neonates had clinical or biochemical hyperthyroidism on D2. 12 had high TSH on D2 - 10 normalized at D14; the other 2 were discussed with tertiary referral centre, no further medical treatment was advised and normalized spontaneously. 22 had high T4 at D2; at D14, 14 normalized, 4 had persistent high T4 but normal TSH (T4 data not available on 4 but all had normal TSH). Neonates born to mothers who were using ATD at time of delivery had higher probability of having high TSH at D2 compared to those who were not (8/11 vs 4/20, p<0.005). This difference was not statistically significant based on use of ATD at onset of pregnancy (10/20 vs 2/11, p=0.08). Conclusion: Our study showed that no neonates developed overt hyperthyroidism. Use of ATD, especially in third trimester, could be associated with risk of transient biochemical hypothyroidism in neonate. A coordinated multidisciplinary care pathway is required to monitor and manage this complex cohort of patients and neonates.