| Objective: 1)To observe the iodine intake of healthy pregnant women at zero iodine balance,and to explore the recommended iodine intake of Chinese women with different gestational stages.2)To explore the range of 24 hour urinary creatinine excretion in healthy Chinese pregnant women,and a possible method for evaluating iodine nutritional status in pregnant women by using the data of urinary iodinecreatinine ratio.Method: The iodine balance study took healthy Chinese pregnant women as the object including the early,middle and late pregnancy in three regions of Shandong province,Tianjin City and Hebei Province.For seven consecutive days,duplicate diets,drinking water,24-hour urine samples,and daily feces of the pregnant women were collected and record the daily water intakewas recorded.The iodine content of each sample was detected and estimate daily iodine intake by inspiration and iodine excretion by both expiration and sweat.Calculate the daily total iodine intake and excretion.According to the iodine balance value is equal to the iodine intake minus the iodine output,the iodine intake at the zero iodine balance is calculated by the model fitting.Experimental animal models with different iodine intakes were established to explore the possible explanation of the phenomenon that the zero iodine balance value increased with the iodine intake in pregnant women during the iodine balance experiment.The urinary iodine-creatinine ratio using to evaluating iodine nutrional status on pregnant women was studied in healthy Chinese pregnant women recruited in the iodine balance experment with different iodine nutrition status.The rational application of urinary iodine-creatinine ratio was discussed by calculating the mathematical model.Results: Data from 122 volunteers were included in the analysis.The average age of the volunteers was 29.8 years and the average gestational age was 22.0 weeks.The analysis data included balanced experiment samples at 773 days,including data of 3092 double meal samples,773 drinking water samples,773 24 hour urine samples and 559 fecal samples.Total daily iodine intake in early,middle and late pregnancy was 271.2μg/d,274.9μg/d and 315.6μg/d,respectively,and there was no statistical significance(P=0.05).Total daily iodine output was 220.0μg/d,293.2μg/d and 287.5μg/d,respectively,and there was no statistical significance(P=0.06).There was no statistically significant difference in iodine balance between different gestation periods(P=0.66).The corresponding zero-iodine balance value of early,middle and late pregnancy,namely the intercept of fitted line and X axis,was 353.0 μg/d,310.6 μg/d and 314.4 μg/d,respectively.The total zero iodine balance value is 313.2 μg.The analysis found that the daily total iodine intake and total iodine output of pregnant women who lived in areas with high water iodine for a long time were higher than those who lived in general environment and the calculated iodine zero iodine balance is also higher than that of pregnant women living in the general environment.The results for this population were confirmed in animal models.In the present study,the average 24 hour urinary creatinine excretion in pregnant women was 1.17(95%CI 1.11,1.22)g.The 24 hour urinary creatinine excretion in different gestation periods was no statistical significance(P=0.119).The range of 24-hour urinary iodine excretion was(33,2022)μg/d,the range of urinary iodinecreatinine ratio was(32,1203)μg/g,the range of daily iodine intake was(26,2139)μg/d.Compared with urinary iodine concentration,urinary iodine-creatinine ratio has a greater correlation with 24 hour urinary iodine output and daily iodine intake(P<0.05).Urinary iodine-creatinine ratio can better reflect 24 hour urinary iodine output and daily iodine intake than urinary iodine concentration.The ideal values of 24 hour urinary iodine output and daily iodine intake were determined with the urinary iodine-creatinine ratio of 5μg/g as the interval,and the comparison table was drawn to facilitate the query.Conclusions: 1)The total calculated zero-iodine balance value for pregnant women was 313.2μg/d.2)The calculated iodine balance value increases in pregnant women who consume excessive iodine over a long period of time.3)The 24 hour urinary creatinine excretion in healthy Chinese pregnant women was 1.17 g,the ideal values of 24-hour urinary iodine excretion and daily iodine intake corresponding to the urinary iodine-creatinine ratio were calculated and listed out. |
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