| Iodine plays an important role in thyroid function.Iodine is an essential nutrient for the synthesis of thyroid hormones,which are critical to fetal brain development and metabolic processes in the body throughout life.As thyroid hormone production increases,kidney iodine loss increases and fetal iodine demand increases,iodine demand in pregnant women increases by ? 50%.Therefore,the risk of iodine deficiency disorders increases during pregnancy.Knowledge regarding iodine nutrition usually affect iodine status during pregnancy.Once a pregnant woman is in a state of iodine deficiency for a long time,it may bring irreversible intellectual damage to the fetus.At present,the index of iodine nutrition evaluation is usually the median urinary iodine(MUIC)and diet survey.Thyroid function indexes usually include thyroid stimulating hormone(TSH),free thyroxine(FT4),free triiodothyronine(FT3)and thyroid peroxidase antibody(APOTb).Method: The research method is divided into two parts.The first part This was a cross-sectional study that enrolled pregnant women who visited the Eastern Hospital of Shanghai Sixth People's Hospital in Shanghai for a routine antenatal checkup between October 2017 and July 2018 and with basic information,two questionnaires and blood samples were collected.We recruited 145 pregnant women(12–16 weeks gestation),101 pregnant women(24–28 weeks gestation)and 108 pregnant women(34–38 weeks gestation).Questionnaires are all prepared in a unified way and pre-investigated,which are investigated and filled in by qualified investigators.The two questionnaires refer to:(1)iodine related knowledge questionnaire,in order to understand pregnant women's knowledge about iodine nutrition.(2)Food Frequency Questionnaire,in order to understand the recent food types,intake and frequency of pregnant women,and evaluate the dietary iodine intake level of pregnant women.In order to improve the accuracy of food survey,food models are presented for all parts involving food.Distributing measuring barrels to pregnant women and informing 24-hour urine collection methods,collecting 24-hour urine samples,and inductively coupled plasma mass spectrometry(ICP-MS)were used to measure iodine concentrations in the urine;fasting blood samples of pregnant women were collected by professional medical staff and thyroid function related indexes TSH,FT3,FT4 and TPOAb in their serum were measured.The second part: Follow up pregnant women for 34-38 weeks and measure the heel blood TSH and growth quality indexes(body length,head circumference,birth weight and sex)of the newborn.SPSS20.0 software was used to process the data.The aims of the present study were to assess the iodine status of pregnant women in Shanghai,and their knowledge regarding iodine,with the goal of investigating to the relationship between iodine and thyroid function during pregnancy.Results:The awareness rate of iodine-related knowledge among women in the second and third trimester of pregnancy in Shanghai was only45.65%,and there was a general lack of correct understanding of iodine nutrition.A total of 354 healthy pregnant women were enrolled in the current study.In the survey of354 healthy pregnant women,we received 349 questionnaires on iodine-related knowledge,253 questionnaires on dietary frequency(FFQ)and 354 blood samples.Regarding the data collection of newborn babies born to pregnant women in the third trimester of pregnancy,we have collected 88 cases of newborn babies.Regarding iodine related knowledge questionnaire,we know that few people know it is harmful to fetus(8.3%);only 9.7%knew the recommended daily iodine intake.44.1%of pregnant women can correctly store iodized salt.The score of knowledge about iodine of pregnant women with high education was higher than that of pregnant women with low education(Z=-5.413,P<0.001).The median 24-h urinary iodine concentration(MUI)of the 354 pregnant women was 119.2?g/L(interquartile range(IQR)84.5–167.5?g/L),and 68.9%and 23.7%had urinary iodine levels<150?g/L and 150–249?g/L,respectively.The median UIC of pregnant women in weeks 12–16,24–28 and 34–38was 116.9?g/L,113.0?g/L and 124.9?g/L,respectively.There was no significant difference between the gestational age groups(P>0.05).The median urinary iodine excretion of pregnant women in weeks 12–16,24–28 and 34–38 were 209.5?g,218.2?g,and 214.3?g,respectively.The median urinary iodine output during the 24 hours of pregnancy was 214.2?g.The median 24-hour urinary iodine excretion(UIE)of 354pregnant women was 214.2?g g.The median UIE of pregnant women in weeks 12–16,24–28 and 34–38 were 209.5?g,218.2?g and 214.3?g respectively.Among the 354pregnant women,the concentration of free triiodothyronine(FT3)in pregnant women aged 12-16 weeks,24-28 weeks and 34-38 weeks was 5.12±0.60 pmol/L,4.42±0.61pmol/L,4.40.±0.57 pmol/L;free thyroxine(FT4)concentrations were 16.10±2.38pmol/L,13.82±1.79 pmol/L,12.99±1.77 pmol/L,respectively;thyroid stimulating hormone(TSH)concentration was 1.58 m IU/L,1.98 m IU/L,2.10 m IU/L.With the progress of gestational age,the TSH of pregnant women increased significantly(P<0.001),and FT3 and FT4 decreased significantly with the increase of TSH(P<0.001).There was a positive correlation between 24h urinary iodine excretion and TSH in pregnant women aged 12-16 weeks(r=0.167,P<0.05),and a negative correlation with FT4(r=-0.272,P<0.01).In the other two groups,Urinary iodine index of pregnant women is not correlated with thyroid hormone level and TSH level.According to the iodine nutritional status of WHO,the thyroid hormone level and TSH in the low iodine group(UIC<150?g/L)were not significantly different from those in the iodine-adapted group(UIC:150-250?g/L)and TSH.(P>0.05).The results of 253FFQ questionnaires showed that the dietary iodine intake of pregnant women was 287.4?g/d,while the 24 h UIE of these 254 pregnant women was 209.9?g/d.The estimated dietary iodine intake of FFQ was related to 24h UIE(Spearman correlation):r=0.440,p<0.001).In addition,among the 349 pregnant women,the proportion of iodized salt consumed per day was only 78.0%.The MUI of pregnant women who consumed iodized salt daily was significantly higher than that of pregnant women who consumed non-iodized salt daily(Mann-Whitney U,Z=-5.087,P<0.001).Among the88 neonates born in the third trimester,the birth weight of boys of different sexes was higher than that of the girls,and the difference was significant(P<0.05).According to the urinary iodine concentration group,the change of neonatal TSH level in the low iodine group(UIC less than 150?g/L)was not significant(P>0.05)compared with the TSH level in the neonatal iodine group(UIC 150-249?g/L).The birth quality of 88newborns was good.Conclusion:According to WHO's criteria,this study emphasizes that the iodine nutritional status of pregnant women in the coastal city of Shanghai is in a state of mild iodine deficiency.Insufficient dietary iodine intake and wrong iodine nutritional behavior are the main factors of iodine deficiency in coastal areas.Strengthening public health education is a necessary condition for achieving appropriate iodine status.Otherwise,the risk of iodine deficiency in pregnant women may continue to increase.In this study,thyroid hormone levels in healthy pregnant women with negative thyroid peroxidase antibodies were not associated with urinary iodine levels.In pregnant women with normal thyroid function,mild iodine deficiency in the third trimester may not be harmful to the pregnancy outcome,but the sample size of the newborn is not large and requires a large amount of data for further verification.The WHO cut-off point of 150?g/L may be too high for pregnant women in China,but it still needs a lot of research to confirm it.Currently,the potential harm of mild iodine deficiency is unclear.Mild to moderate iodine deficiency has less impact on cognition than severe iodine deficiency,but it is still important.Therefore,we should dynamically monitor pregnant women's iodine nutrition and screen the neonatal TSH positive rate as a means of improving the quality of the people for a long time. |
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