Thyroid function in infants born to women with hypothyroidism: An observational study at an Australian tertiary perinatal centre

Abstract:

Objective: Concerns have been raised regarding thyroid dysfunction in infants born to women with hypothyroidism including those with autoimmune hypothyroidism. This concern has led to the practice of thyroid function testing in the early neonatal period. We evaluated the practice of performing a routine thyroid function test around 2 weeks of age in all healthy full-term infants (≥37 weeks gestation) born to women with hypothyroidism to identify thyroid dysfunction.
Design, patients, and measurements: This retrospective, observational single centre study included full-term infants born to women with hypothyroidism, including non-Graves' autoimmune hypothyroidism, over a 3-year period. Preterm infants and those born to women with Graves' disease or thyroidectomy were excluded.
Results: Of the 790 mother-infant dyads, 780 infants (99%) had normal thyroid function. Only 10 infants (1%) had thyroid stimulating hormone (TSH) levels > 10mIU/L at 2 weeks of age (range 10.25-106.37 mU/L). Of these, follow-up thyroid function normalized in nine infants within 2 weeks. A routine newborn screening test identified congenital hypothyroidism in one infant. No infant born to women with known presence of anti-thyroid antibodies had TSH levels > 10 mIU/L. Thyroid function was normal for most infants where maternal anti-thyroid antibodies were not known (125/133, 94%).
Conclusions: Infants born to women with hypothyroidism (including autoimmune hypothyroidism) had normal thyroid function in the early neonatal period. A small proportion of infants may develop TSH levels > 10 mU/L that normalizes by 4 weeks of age. The practice of routine thyroid function testing for this cohort in addition to newborn screening test offers no additional benefit.

Audience Takeway:

• Outcome of thyroid function test of infants born to women with hypothyroidism at 2 weeks of age.
• May have implications on monitoring practice in some centers who still repeat TFT at 2 weeks, which can result in better utilization of hospital resources.
• May provide further research ideas.

Biography:

Dr. Perez is a dual-trained paediatrican and neonatologist. She studied Bachelor of Science in Pharmacy at the University of the Philippines and Doctor of Medicine at St Lukes’ College of Medicine in 2008. She completed her pediatric residency training at St. Luke’s Medical Center and served as chief resident in 2012. Dr. Perez completed further pediatric training at the Children’s Hospital at Westmead, Australia and became a fellow of the Royal Australasian College of Physicians in Paediatrics and Child Health. She pursued post fellowship training in neonatology and is currently working as a neonatologist in Grace Centre for Newborn Intensive Care at The Children’s Hospital at Westmead, Sydney, Australia.