RESUMEN
Objective:To study the iodine nutritional status of pregnant women in the third trimester in the Southwest of Shandong Province, analyze its impact on their cardiac electrical activity, and provide a basis for scientific supplementation of iodine during pregnancy.Methods:From January 2021 to June 2022, a cross-sectional survey was conducted using cluster random sampling method. According to the inclusion and exclusion criteria, 200 pregnant women in the third trimester were selected from 3 tertiary hospitals in three cities in the Southwest of Shandong Province, and were divided into the third trimester group ( n = 600), and 100 non-pregnant women were selected as the control group ( n = 300). The urinary iodine content was detected by arsenic-cerium catalytic spectrophotometry, and the pregnant women in the third trimester group were subdivided into iodine deficiency subgroup [G1 subgroup, median urinary iodine (MUIC) < 150 μg/L] based on the MUIC, iodine excess subgroup (G2 subgroup, MUIC≥500 μg/L) and moderate iodine subgroup (G3 subgroup, 150 μg/L≤MUIC < 500 μg/L). Chemiluminescence immunoassay was used to measure the serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT 4) and free triiodothyronine (FT 3). The cardiac electrical indexes were detected by a 12-lead surface electrocardiogram (ECG) machine. Results:There was no statistically significant difference in urinary iodine levels between pregnant women in the third trimester group and non-pregnant women in the control group among the 3 tertiary hospitals in the Southwest of Shandong Province ( H = 3.63, 3.27, P > 0.05). In the third trimester group, the proportion of pregnant women in the G1, G2 and G3 subgroups was 27.67% (166/600), 6.83% (41/600) and 65.50% (393/600), respectively. There was a statistically significant difference in urinary iodine levels between the subgroups and the control group ( H = 11.56, P < 0.001). The serum FT 3 and FT 4 levels in the G2 subgroup were lower than those in the G1 and G3 subgroups ( P < 0.001), but there was no statistically significant difference in serum TSH levels among the three subgroups ( P > 0.05). The normal rates of ECG in the G1, G2, G3 subgroups, and the control group were 38.55% (64/166), 41.46% (17/41), 92.37% (363/393), and 95.33% (286/300), respectively. The difference between the groups were statistically significant (χ 2 = 461.25, P < 0.001), the normal rate of ECG in the G1 and G2 subgroups was lower than that in the control group ( P < 0.001). Short P-R intervals and ST-T changes were the most common abnormal ECG in the third trimester group. Conclusions:The incidence of iodine deficiency, iodine excess, and other abnormal iodine nutritional status in pregnant women in the third trimester of the Southwest of Shandong Province is relatively high. Short P-R intervals, ST-T changes, and other arrhythmia caused by this are more common. It is necessary to strengthen monitoring of iodine nutritional status and ECG during pregnancy, and adjust intervention strategies such as iodine supplementation in a timely manner.