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Effect of Maternal Iodine Excess during Pregnancy on Neonatal Thyroid Function and Neurodevelopmental Status at 12
Deepashree K Rao1, Ankur Jindal2, Aashima Dabas1
1Department of Pediatrics, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi, India.
Insights
Maternal iodine excess during pregnancy can cause temporary thyroid issues in newborns. However, this iodine excess did not impact infant growth or neurodevelopment by three months of age.
Area of Science:
- Endocrinology
- Neonatal Health
- Public Health
Background:
- Iodine is essential for thyroid hormone production.
- Iodine excess during pregnancy may pose risks to both mother and fetus.
- Maternal iodine status can influence neonatal thyroid function.
Purpose of the Study:
- To investigate the effects of maternal iodine excess on neonatal thyroid function.
- To assess the impact of maternal iodine excess on infant growth and neurodevelopment up to 12 weeks of age.
Main Methods:
- Prospective study of term neonates born to mothers with high urine iodine concentration (UIC ≥500 µg/L).
- Neonatal thyroid-stimulating hormone (TSH) measured via heel prick at birth, 2, and 12 weeks.
- Maternal UIC and neonatal growth and development were monitored.
Main Results:
- 25.4% of mothers had elevated UIC; 12.2% of neonates showed elevated TSH at birth.
- Transient hyperthyrotropinemia observed in neonates, with TSH levels normalizing by 12 weeks in most cases.
- Maternal iodine levels showed a weak correlation with neonatal TSH at 2 weeks (p=0.037).
- No congenital hypothyroidism requiring treatment was diagnosed.
- Neonatal growth and development were comparable between infants with and without TSH elevation at 3 months (p>0.05).
Conclusions:
- Maternal iodine excess during pregnancy and the peripartum period can lead to transient hyperthyrotropinemia in neonates.
- This transient condition did not adversely affect neonatal growth or neurodevelopment at three months of age.
Objective:
This study aims to determine the effect of iodine excess in pregnant mothers on thyroid function, growth and neurodevelopment in the neonates when assessed at 12 weeks of age.
Methodology:
This prospective study enrolled term neonates with birth weight >2500 gm of mothers having urine iodine concentration (UIC) ≥500 µg/L documented in the third trimester of the peripartum period. Neonatal TSH was collected by heel prick on dried blood spots within 24-72 hours of age and measured by time-resolved fluroimmunoassay. Neonates with TSH ≥11 mIU/L at birth were followed up at 2 and 12 weeks to monitor thyroid dysfunction, growth and development.
Results:
A total of 2354 (n = 1575 in the delivery room) maternal urine samples were collected of which 598 (25.4%) had elevated UIC. Forty-nine (12.2%) neonates had TSH ≥11mIU/L on newborn screening of whom 18 and 3 neonates had residual elevated TSH at 2 and 12 weeks of life, respectively. Maternal iodine levels correlated weakly with TSH at 2 weeks (rho = 0.299; p = 0.037). No child required treatment for congenital hypothyroidism. Eight babies additionally had TSH >5 mIU/L at 12 weeks of life. The growth and development of babies with or without TSH elevation was comparable at three months (p >0.05).
Conclusion:
Maternal iodine excess in pregnancy and peripartum period causes transient hyperthyrotropinemia in neonates that did not affect the growth and development at 3 months of age.
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