Inconsistencies in the management of neonates born to mothers with "thyroid diseases"

Benefits of rescreening newborns of mothers affected by autoimmune hypothyroidism

Introduction

Infants of mothers with autoimmune hypothyroidism (AH) are at risk of developing late-onset hypothyroidism, often escaping at newborn screening. This condition might be caused both by the action of maternal antibodies and/or by maternal treatment.

Objectives

The aim of this study is to evaluate the prevalence of AH in the mothers of children born in Veneto region, Italy, and to define what is the most appropriate management for these newborns.

Methods

Newborns of six different hospitals with a mother suffering from AH and with negative neonatal screening for congenital hypothyroidism (CH) were included in the study. Between 15 and 20 days of life, we collected a serum sample for the evaluation of thyroid function (thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3)) and anti-thyroid antibodies. On the same occasion, a capillary blood sampling was performed for a second screening test.

Results

Maternal AH has a prevalence of 3.5%. A total of 291 newborns were enrolled from November 2019 to May 2021. Whereas the 11.4% of infants had a slight elevated serum TSH (>6 mU/L) and required a follow-up, only 2 children presented an elevated TSH level at the second screening test. One of these, with the gland in situ, showed persistently elevated serum TSH levels and required treatment with levothyroxine.

Conclusions

Maternal AH rarely caused neonatal thyroid dysfunction. We suggest to reassess newborns from mothers with AH 15 days after birth by means of a second neonatal screening test. This procedure avoids false negatives due to maternal thyroid status, is less invasive and cheaper than the serum TSH evaluation, and prevents a long follow-up.

Comparison of the offspring ultrasound thyroid volume in hypothyroid mothers treated with different levothyroxine doses: A cohort study

PURPOSE

We aimed to determine the volume of the thyroid gland in full-term neonates born to hypothyroid mothers as compared with full-term infants born to healthy mothers and to investigate the association between levothyroxine doses and the thyroid volume of neonates.

MATERIALS AND METHODS

This is single center prospective observational study of 245 full-term neonates (96 from hypothyroid and 149 from healthy mothers). Ultrasound examination in both longitudinal and transverse projections was used to calculate the thyroid volume applying the ellipsoid formula.

RESULTS

Median (interquartile range) thyroid volume of newborns from hypothyroid mothers was significantly smaller compared to the control group with regard to the total thyroid volume and the left lobe (p < 0.05). We found no statistically significant difference for the right lobe (p > 0.05) and inverse correlation between the thyroid volume and levothyroxine doses taken by mothers.

CONCLUSION

Results of the present study indicate that maternal thyroid hormone levels may interfere with the fetal hypothalamic-pituitary axis.