The Impact of Iodized Oil Injection in The Pregnant Women on the Thyroid Function of Their Neonates and Infants

Previous studies have clearly shown that the injection of iodized oil in the pregnant women may be a prophylactic strategy for IDD (Iodine Deficiency Disorders) and could improve the growth indices of their offsprings. Since the administration of pharmacological doses of iodine may occasionally lead to large goiter and rarely hypothyroidism, in the present study the thyroid function tests of the neonates and infants born to women who received 1 ml (480 mg) of iodized oil (Lipiodol) intramuscularly during pregnancy in the years 1993-94 were assessed and compared to control group. Two hundred sixty nine cord blood samples from Mazandaran and Kohkiluyeh & Boyerahmad provinces, 117 in the experimental (injected) and 152 in the control (noninjected) group and 1015 blood samples of the neonates and infants from Mazandaran province consist of 539 in the experimental and 476 in the control groups were obtained and T4, T3, and TSH concentrations were measured with commertial RIA Kits. In the cord samples in whom the iodized oil was administered in the second trimester of pregnancy, T4 was lower than the control group: 10.8±2.6 vs 11.6±2.6 µg/dl, respectively (P<0.01). T, and TSH concentration did not differ: 56±30 vs 60±31 ng/dl and 8.2± 5.6 vs 6.9±5.3 µU/ml, respectively. In the neonates and infants, T4 and TSH concentrations did not show any significant difference(s) between the experimental and control groups: 13.8±3.1 vs 13.1±3.1 µg/dl and 2.8 ±4.7 vs 3.4 ±6.3 µU/ml, respectively. Mean T, concentration in the experimental group was higher than control: 228 ±78 vs 198±82 ng/dl, respectively (P<0.001). T3, concentrations in infants born to mothers injected in the first, second and third trimester of pregnancy were 198±50, 233±75 and 242 ±81 ng/dl, respectively. TSH concentrations were higher in those subjects being injected iodized oil in the first trimester of pregnancy than in the second trimester: 3.4±2.0 vs 2.3±1.5 µU/ml, respectively (P<0.001). In conclusion, iodized oil injection during pregnancy would not lead to any significant alteration(s) in T4, and TSH concentrations in the cord blood samples and also in the neonates However, it may increase T3, concentration and this increment was closely related to the time of injection and delivery.