The Effect of Iodine Intakes on Maternal and Infant Health and the Study of Iodine RNI for Different Stages of Pregnancy
The Effect of Iodine Intakes on Maternal and Infant Health and the Study of Iodine RNI for Different Stages of Pregnancy
This study determined the effects of different iodine intake on the maternal and infant
 health and provide evidence for studying the RNI and UL of iodine in pregnant women.

 1. The study of effect on mothers and their infants of the lack of iodine at different
 gestation in adequate iodine area.

 The purpose of this study was to detect the maternal thyroid function, growth and
 neuropsychological development of infants in different pregnancy women with diverse
 iodine intake levels, and to make a clear evaluation for the influence of iodine
 deficiency during different pregnancy by following up iodine suitable early pregnancy
 women and mild iodine deficient three pregnancy women as well as their infants.

 2. The study of recommended iodine intake (RNI) for healthy pregnant women in three
 pregnancy.

 Different pregnancy women with different iodine intake levels were recruited and carried
 out iodine balance experiment in the case of not interfering with their diet. In
 addition, the iodine intake of the pregnant women when they reached "zero iodine
 balance" was calculated, that was EAR of iodine in pregnant women. In conclusion, the
 iodine balance experiment in pregnant women at different pregnancy improved the sample
 collection methods and evaluation criteria and was more scientific and reasonable than
 the classic iodine balance experiment.

 3. The study of effect of different levels of high iodine exposure on pregnant women,
 delivery women and their infants.

 In this study, we made a prospective study of the early pregnancy women and their infants
 exposed to different high iodine levels in high water iodine areas. At first we defined the
 effects of long-term iodine excess exposure on the health of the mother and the infants by
 combining with the reference index of the normal value of the thyroid function in different
 maternal and postpartum periods, the level of growth and development of the offspring and the
 assessment of the level of neuropsychological development. Furthermore the harmful effects of
 different high levels of iodine exposure on pregnant women was synthetically analyzed. This
 study obtained the safe intake level of iodine for pregnant women and provided scientific
 basis for the formulation of iodine UL in pregnant women in China.
1. The relationship between iodine deficiency during pregnancy and maternal offspring health

 1. Screening of pregnant women with iodine deficiency:

 A prevalence survey of pregnant women was conducted in iodine-sufficient area, combined
 with the results of single spot urinary concentration, 24h urinary iodine concentration
 and thyroglobulin level, screening out pregnant women with iodine deficiency during
 first, second and third trimester of pregnancy. There are 60 pregnant women in each
 group. At the same time, 60 pregnant women with iodine-sufficient during early pregnancy
 were selected, and the total number of the four groups is 240.

 2. Effects of iodine deficiency on pregnant women during different pregnancy:

 Pregnant women with iodine deficiency were gived nutritional guidance, and were advised
 to take iodine supplements. Follow-up with regularly collecting fasting venous blood,
 dried whole blood and single spot urine was conducted, in order to dynamically grasp the
 iodine nutritional status and thyroid function of pregnant women during different
 pregnancy, and clarify the influence of iodine deficiency on pregnant women in each
 group.

 3. Effects of iodine deficiency on offspring during different pregnancy:

 The offspring of follow-up pregnant women were observed, collecting the heel blood at
 birth for measuring TSH, and performing physical examination. Assessment of
 neuropsychological development in offspring for two years after delivery was performed ,
 in order to clarify the effects of iodine deficiency on the neuropsychological
 development of offspring in each group.

 4. Statistical analysis:

 Normally distributed variables were reported as the mean ± standard deviation, comparison
 between groups were analyzed with the use of t-test or analysis of variance (ANOVA), and
 Pearson linear correlation was used for correlation analysis; Urinary iodine level is
 lognormal distribution, so it was converted into logarithmic form and then analyzed.
 Non-normally distributed variables were presented as median and interquartile range. The
 Wilcoxon rank sum test was used for comparison between groups, and correlation analysis was
 performed using the Spearman rank correlation test. The chi-squared test was adopted for the
 comparison of enumeration data. P values below 0.05 was considered statistically significant.

 2. Study the RNI of iodine on pregnant women during different pregnancy:

 1. Screening of pregnant women during different pregnancy:

 A prevalence survey of pregnant women was conducted in iodine-sufficient area, based on
 24h urinary iodine concentration, thyroglobulin level, related health check and medical
 history query results, screening out pregnant women who meet the requirements of this
 study during first, second and third trimester of pregnancy. Each group has 20 pregnant
 women, and the total number is 60.

 2. Reasearch of the iodine EAR of pregnant women during different pregnancy:

 Iodine balance studies were performed on healthy pregnant women during first, second and
 third trimester of pregnancy to evaluate the daily iodine intake and excretion,
 including collecting and testing 24h dietary iodine intake, 24h urinary iodine and fecal
 iodine excretion of subjects. The daily respiratory iodine intake and excretion of
 subjects was assessed by measuring the iodine content in the air and exhaled breath. In
 addition, according to the positive correlation between iodine balance value and iodine
 intake, a scatter plot was drawn and curve fitting was performed. According to the
 results of iodine balance experiment, the iodine balance regression curves of first,
 second and third trimester of pregnancy were established , in order to determine the
 level of iodine intake when the pregnant women reach the iodine balance, which is the
 estimated average requirement (EAR) of pregnant women during different pregnancy.

 3. Research of iodine RNI on pregnant women during different pregnancy:

 Based on the obtained EAR values of iodine for different pregnancy and the 20% coefficient of
 variation (CV), according to the formula: RNI=EAR+2CV=1.4EAR, the iodine RNI values of
 pregnant women in different gestation were derived.

 3. Study on the relationship between iodine excess and maternal offspring health and iodine
 UL of pregnant women

 1. Prospective study:

 Pregnant women during early pregnancy who were exposed to different excessive water
 iodine intake were enrolled in a large-scale epidemiological prospective study, in order
 to assess the levels of iodine intake by collecting and testing random urinary iodine
 and 24h urinary iodine levels, and to detect the thyroid function indicators under
 different iodine intake levels to evaluate the health effects and harms of different
 high iodine intake on pregnant women. At the same time, the growth and development of
 the offspring and the level of neuropsychological development were evaluated to
 determine the long-term iodine excess exposure to the health of pregnant women and
 offspring.

 2. Discussion on iodine UL of pregnant women:

 According to the urinary iodine level during pregnancy, the subjects were divided into
 groups with different iodine intakes, with the TSH abnormal rate of pregnant women > 5%
 and the increase of FT3/FT4 as the end point, comprehensively determining the harmful
 effects of different iodine intake on pregnant women and offspring, analyzing the iodine
 safety intake level suitabled for pregnant women, and exploring the iodine UL of
 pregnant women.

 3. Statistical methods:

 Epi-data was used to enter survey data. Univariate statistical analysis was used to analyze
 the differences in evaluation indicators between different iodine intake levels..
 Multivariate statistical analysis methods were used to analyze the safety of each iodine
 intake level under multiple factors.
Inclusion Criteria:

 -  1) aged between 18-35 years old; 2) singleton pregnancy; 3) Living in Tianjin or
 Shandong at least 5 years; 4) no history of any thyroid diseases; 5) no medication or
 supplementation of iodine.