Maternal Graves' disease and fetal tetralogy of Fallot: a case series

Background: Congenital heart defects have been reported with the use of antithyroid medication with ventricular septal defects (VSD) being the most common. As per the current practice guidelines maternal Graves' disease (GD) is not an indication for fetal echocardiogram. Case presentation: We described three neonates with tetralogy of Fallot (TOF) born to mothers with GD. Only one of the mothers was on antithyroid medication. Two of these neonates were diagnosed postnatally when they failed the pulse oximeter congenital cardiac screening and diagnosis was established by postnatal echocardiogram. Two of the mothers had radioactive iodine ablation and were on levothyroxine during pregnancy. The dose of levothyroxine was increased during pregnancy. There was no other complication during pregnancy. The third mother had hyperthyroidism and developed a thyroid storm during pregnancy requiring inpatient admission and treatment with propylthiouracil (PTU), metoprolol and methimazole. All babies had normal thyroid function test postnatally and eventually had successful repair of TOF defect. Conclusion: We report the largest known case series of children with TOF born to mothers with GD. Apart from the isolated reports of fetal TOF in mothers with GD, there is no clear association between fetal TOF and maternal GD and antithyroid medication. Based on the review of the literature and our case series, there may be an increased incidence of congenital heart defects in maternal GD irrespective of antithyroid medication use. This case series may add to the current knowledge base and support routine fetal echocardiogram screening for all mothers with GD.