Iodine exposure and thyroid function after prophylactic intragastric iodinated contrast administration for meconium...

Maternal hypertensive disorders of pregnancy (HDP) increase the risk of meconium obstruction of prematurity in small-for-gestational-age (SGA) extremely low birth weight (ELBW) infants. While prophylactic intragastric amidotrizoate (Gastrografin^®) promotes meconium excretion, concerns persist regarding iodine load and thyroid dysfunction.

We retrospectively analyzed infants (<30 weeks, <700 g) born 2016-2024. The treated group (n=20) comprised SGA infants of mothers with HDP receiving prophylactic 5-fold diluted Gastrografin (iodine: 148-222 mg/kg) after stabilization. Controls included nontreated SGA infants (n=17), mostly lacking maternal HDP (thus not meeting prophylaxis criteria), and an appropriate-for-gestational-age (AGA) reference cohort (n=48). A 2018-2022 unexposed subcohort (n=21) provided baseline urinary iodine concentration (UIC) data.

Treatment failure, necessitating therapeutic enema, occurred in 1/20 treated infants (5 %). Baseline UIC was 32 (IQR 25-127) vs. 25 (IQR 25-35) µg/L in combined controls (p=0.23). Day 1 postadministration, UIC surged to 326,000 (IQR 201,500-455,350) µg/L; by 2 weeks, it normalized to 348 vs. 267 μg/L (p=0.51). At 2 weeks, thyroid function was comparable between treated and nontreated SGA groups for TSH (5.8 vs. 5.1 μIU/mL; p=0.94), free T3 (1.56 vs. 1.55 pg/mL; p=0.68), and free T4 (0.98 vs. 0.78 ng/dL; p=0.31), though baseline HDP differences necessitate careful interpretation. Levothyroxine supplementation rates were 26 % vs. 13 %, respectively (p=0.42).

Early postnatal iodine levels in preterm infants are low. Prophylactic intragastric Gastrografin facilitated meconium evacuation in high-risk SGA ELBW infants. The associated iodine elevation is transient. A nonsignificant numerical increase in levothyroxine supplementation within our small cohort necessitates further large-scale studies.