Iodine Status, Thyroid Function, and Birthweight: A Complex Relationship in High-Risk Pregnancies

Area of Science:

• Endocrinology
• Perinatal Medicine
• Nutritional Science

Background:

• Iodine deficiency and thyroid dysfunction in pregnancy are linked to infant neurodevelopmental issues.
• Limited data exists on iodine, thyroid hormones, and fetal growth in high-risk pregnancies.
• Investigating the impact of adverse antenatal/perinatal conditions on iodine and thyroid parameters is crucial.

Purpose of the Study:

• To examine iodine status and thyroid function in high-risk versus low-risk pregnancies.
• To determine if adverse intrauterine conditions affect fetal growth markers like birthweight.
• To assess the relationship between maternal/fetal iodine and thyroid hormone levels.

Main Methods:

• Cross-sectional study comparing high-risk (HR, n=108) and low-risk (LR, n=233) pregnancies.
• Measured urinary iodine concentration (UIC), amniotic fluid iodine, and cord blood thyroid-stimulating hormone (TSH) and free thyroxine (FT4).
• Analyzed mother-baby pairs at the time of birth.

Main Results:

• Significant differences observed between HR and LR groups.
• Lower amniotic fluid iodine concentration in HR pregnancies (13.11 µg/L) compared to LR (19.65 µg/L).
• Lower cord blood free thyroxine (FT4) in HR pregnancies (15.30 pmol/L) compared to LR (17.06 pmol/L).

Conclusions:

• Adverse intrauterine environments can negatively affect fetal free thyroxine (FT4) availability.
• Fetal iodine metabolism may be compromised by adverse pregnancy conditions.
• These effects are more pronounced in preterm and/or small fetuses.