Neonatal Thyroid Function: Effect of a Single Exposure to Iodinated Contrast Medium in Utero

Purpose: To evaluate the effect of in utero exposure to a single dose of water-soluble intravenous iodinated contrast medium on thyroid function at birth. Materials and Methods: This study was approved by the institutional review board, with waiver of consent, and was HIPAA compliant. Maternal and newborn records were retrospectively reviewed. All pregnant women who underwent multidetector pulmonary computed tomographic angiography because they were suspected of having pulmonary embolism between 2004 and 2008 and newborns resulting from the index pregnancy were included. In all examinations, iohexol was used as the contrast agent. Dose and amount of contrast agent and gestational age at the time of administration of the contrast agent were collected, and thyroxine (T-4) and thyroid-stimulating hormone (TSH) levels were measured at birth. A total of 344 maternal and 343 newborn records were reviewed. A descriptive analysis was performed, and means, standard deviations, and confidence intervals were reported. Results: Mean gestational age at the time of administration of the contrast material was 27.8 weeks 6 7.4. The mean dose of total iodine administered was 45 000 mg/L +/- 7321. All newborns had a normal T 4 level at birth; only one newborn had a transiently abnormal TSH level at birth, which normalized at day 6 of life. This newborn was born to a mother who had many drug exposures during pregnancy. Conclusion: A single, high-dose in utero exposure to water-soluble, low-osmolar, iodinated intravenous products, such as iohexol, is unlikely to have a clinically important effect on thyroid function at birth.