Effects of iodine nutritional status on cardiac electrical signals of pregnant women in the second trimester pregnancy

Abstract

Objective To investigate the effects of iodine nutritional status on cardiac electrical signals of pregnant women in the second trimester pregnancy. Methods From July 2015 to July 2017, a total of 1 600 pregnant women in the second trimester pregnancy were selected from two hospitals in Haiyang City, Shandong Province by convenience sampling method as the observation group, and 800 healthy non-pregnant women with normal iodine nutritional status were selected in the principle of age-matched as the control group (C group) during the same period in the same hospitals and by the same method. The iodine nutritional statuses of pregnant women in observation group were measured, and the electrocardiograms of all subjects were analyzed. According to the results of iodine nutritional status, the pregnant women in the second trimester pregnancy were divided into iodine deficiency subgroup (G1 subgroup), iodine excess subgroup (G2 subgroup), and iodine sufficiency subgroup (G3 subgroup), respectively. The rates of normal and almost normal electrocardiogram and the incidence of sinus arrhythmia and the other abnormal electrocardiogram results were compared by chi-square test. The study protocol was performed in accordance with the Helsinki Declaration of the World Medical Association revised in 2013, and clinical research informed consents were obtained from all participants. Results ①There were 502 pregnant women in the second trimester pregnancy at the status of iodine deficiency, 179 cases of iodine excess, and 919 cases of iodine sufficiency. They were divided into G1, G2 and G3 subgroup, respectively. There were no statistical differences among 3 subgroups in age and gestational age (P>0.05). There was no statistical difference among 3 subgroups and C group in age (P>0.05). ②There was statistically significant difference in rate of normal and almost normal electrocardiogram among 3 subgroups in observation group and C group (χ2=79.889, P 0.05). ④There were statistically significant differences on the abnormal results of electrocardiogram examination in the pairwise comparison in sinus bradycardia (G1 subgroup vs C group: χ2=19.659, G2 subgroup vs C group: χ2=17.409, G1 subgroup vs G3 subgroup: χ2=20.592, G2 subgroup vs G3 subgroup: χ2=17.703, all P<0.001), sinus tachycardia (G1 subgroup vs C group: χ2=17.433, G2 subgroup vs C group: χ2=35.622, G2 subgroup vs G3 subgroup: χ2=16.992, all P<0.001), sinus arrhythmia (G1 subgroup vs C group: χ2=178.673, G2 subgroup vs C group: χ2=110.717, G1 subgroup vs G3 subgroup: χ2=168.011, G2 subgroup vs G3 subgroup: χ2=93.579, all P<0.001), ventricular premature beats (G1 subgroup vs C group: χ2=14.593, G1 subgroup vs G3 subgroup: χ2=13.472, all P<0.001), short P-R interval (G1 subgroup vs C group: χ2=43.563, G2 subgroup vs C group: χ2=19.291, G1 subgroup vs G3 subgroup: χ2=20.191, all P<0.001), and ST-T changes (G1 subgroup vs C group: χ2=19.796, G2 subgroup vs C group: χ2=23.314, G2 subgroup vs G3 subgroup: χ2=10.630, all P≤0.001) among G1, G2, G3 subgroup and C group. Conclusion Imbalance of iodine nutritional status of pregnant women in the second trimester pregnancy can lead to abnormal electrocardiogram. Key words: Hypothyroidism; Cardiac electrophysiology; Electrocardiography; Iodine; Pregnancy trimester, second; Pregnancy outcome; Controlled clinical trial; Pregnant women