Endocrine Abstracts

Background: Guidelines from ATA and the Endocrine society suggest the use of fetal thyroid monitoring in maternal Graves’ disease to detect fetal thyrotoxicosis or hypothyroidism in response to maternal thyroid receptor antibodies (TRAb) or thionamide therapy respectively. The literature examining how effective this policy is remains sparse, since these remain unusual clinical situations for most centres. Here we review our experience of scanning for fetal goitre.

Methods: Normative data for fetal thyroid size were established at Princess Royal Maternity Unit, Glasgow in 2008. Since then women with a history of Graves’ disease have been routinely scanned using transabdominal ultrasound at 4 weekly intervals from 20 weeks if indicated by positive TRAb or thionamide treatment after 20 weeks. Case notes and electronic records were reviewed for women scanned between 2008–2018.

Results: 18 women were scanned. At the outset of pregnancy 6 were on carbimazole, 4 on propylthiouracil, 3 on thyroxine (2 with previous radioiodine therapy and 1 with previous thyroidectomy) and the remainder on no medications. Possible fetal goitre (>95^th centile) was detected in 2 women. In the first, reduction of PTU dose (despite elevated maternal fT4 levels) at 30 weeks of gestation led to reduction in size of fetal goitre. The second woman had severe T3-toxicosis and grossly elevated TRAb levels; fetal goitre was associated with signs of advanced bone age but without other late signs of fetal thyrotoxicosis. Carbimazole was increased and fetal goitre reduced in size. Baby delivered with normal thyroid function but went on to have neonatal thyrotoxicosis.

Discussion: Even in a relatively large centre (6500 annual deliveries), fetal thyroid ultrasound is needed in relatively few cases, requiring little additional resource since these women are relatively high risk and would be undergoing growth scanning. Nevertheless implementation has led to important changes in management in certain cases.