Iodine exposure and thyroid function after prophylactic intragastric iodinated contrast administration for meconium obstruction of prematurity in extremely low birth weight infants.

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.