Iodine Nutrition During Pregnancy And Its Effects On Infants’ Growth And Development

Objective: These studies were i)to explore the changes of thyroid function and prevalence of thyroid diseases in women among different trimesters and urinary iodine concentration(UIC)in Tianjin and Wuqiang.ii)to follow up the iodine nutrition in lactating women and infants,and then analyze the impact of iodine status during pregnancy and lactation on infants’ thyroid stimulating hormone(TSH)and iodine status.iii)to evaluate the effects of UIC,thyroid function and serum iodine during pregnancy and neonatal TSH on physical and neuro-development of children.Method: From Mar 2016 to Jun 2018,pregnant women was enrolled from Tanggu,Tianjin and Wuqiang,Hebei.Spot UIC were determined,venous blood were to measure free triiodothyronine(FT3),free thyroxine(FT4),TSH,thyroid peroxidase antibody(TPOAb),thyroglobulin antibody(Tg Ab),total serum iodine(TSI)and nonprotein bound serum iodine(nb SI).Neonatal heel-blood was obtained to determine TSH,spot breast milk and urine were collected at 1 and 4 wks postpartum to measure breast milk iodine concentration(BMIC)and UIC.When children were at 18～24 months,physical information,fingertip blood TSH and spot UIC were obtained,neurodevelopment was assessed by GESELL developmental scale.Results: 833 pregnant women were recruited from Tianjin and and 628 form Wuqiang.The UIC was 174(113,249)μg/L and 111(63,167)μg/L,respectively.UIC,FT3 and TSH in Wuqiang pregnant women were lower,and FT4,TSI,nb SI,and the positivity of TPOAb and Tg Ab were higher(P<0.001).FT3,FT4,TSI and nb SI positively correlated with UIC and negatively correlated with TSH in both regions,UIC negatively correlated with TSH only in Tianjin(P<0.05).UIC,FT3,FT4,TSI,nb SI and Tg Ab positivity in Tianjin decreased across pregnancy(P<0.001),while TSH increased(P<0.001)and no difference was found in TPOAb positivity.No significance was found in TSI and nb SI across pregnancy in Wuqiang,changes of other biomarkers coincided with Tianjin.FT3,FT4,TSI and nb SI increased in Tianjin and UIC,FT3 and nb SI increasedin Wuqiang(P<0.05),the rest indicators kept stable.In Tianjin,the thyroid dysfunction rate was 4.9%,in which hypothyroxinemia was the main thyroid dysfunction,lower than that in Wuqiang(8.6%)(P<0.001),increased along with UIC and peaked at UIC ≥500μg/L(P=0.002).In Wuqiang,thyrotoxicosis,as the main thyroid disorders,showed a "U" shape relationship with UIC,the rate was lowest at UIC within 100～149μg/L.The iodine status in lactating women and infants were adequate in Tianjin.There were positive correlations among BMIC,maternal and infant UIC(P<0.01).When UIC or BMIC in lactating women was <100μg/L,infant UIC was lower(P<0.001).UIC during pregnancy positively correlated with matermal UIC at 1 wk postpartum and BMIC at 4 wks postpartum(P<0.05).TSH during pregnancy positively correlated with BMIC and infant UIC at 1 wk after birth(P<0.05).No correlation was found between neonatal TSH and UIC/TSH during pregnancy.With maternal TSH ≥2.5m IU/L,neonatal TSH was higher and rate of ≥5.0m IU/L increased(P<0.05).Neonatal TSH only correlated to maternal TSH,and infant UIC correlated with maternal BMIC and UIC(P<0.05).With UIC during pregnancy within 100～149 μg/L,head-for-age Z-scores was higher(P=0.01).With neonatal TSH ≥4.0m IU/L,length-for-age Z-scores was lower and TSH was higher in children(P<0.01).TSH during pregnancy and infancy was positively related to TSH in children(P<0.01).With maternal UIC≥250μg/L,the risk of development quotient(DQ)≤85 in adaptive domain increased to 2.38 fold(95%CI: 1.06,5.35).The personal-social DQ positively correlated to maternal UIC within 100～149μg/L(P=0.046).An increasing risk of fine motor delay was along with maternal TSH ≥2.5m IU/L(P=0.009).FT4 negatively correlated with personal-social DQ,when lower than the 25 th percentile,negatively correlated to fine motor DQ(P<0.05).TSI higher than the 95 th percentile increased language delay risk to 3.06 fold(95%CI: 1.09,8.58).When neonatal TSH higher than the 75 th percentile negatively correlated with language and personal-social DQ,when lower than the 25 th percentile negatively correlated with personal-social DQ(P<0.05).Conclusion: 1.Changes in UIC,FT3,FT4,TSI,nb SI,Tg Ab positivity and thyroid dysfunction rate during pregnancy in Tianjin and Wuqiang were different.2.Neonatal TSH was related to maternal TSH.Infants UIC was related to BMIC and UIC of lactating mother.3.Maternal UIC,TSH,FT4 and TSI and neonatal TSH correlated with physical and neuro-development of children.