The Association Between Levels Of Serum Phthalate Monoesters And Thyroid Function In Pregnant Women

Background The worldwide use of phthalate lead to the exposure in humans andwildlife by ingestion, inhalation, dermal absorption and so on. As vulnerable population,pregnant women which were exposed to the phthalate not only affect their health, butalso have adverse effect on their fetus. Previous studies found the maternal phthalateexposure had advers effects on reproductive and development system. Someinvestigators reported the thyroid dysfunction of phthalate exposure. The normal thyroidfunction was crucial to the growth and neurodevelopment of fetus. To date, thepopulation studies and experiments which examine the relationships between phthalateexposure and thyroid function in pregnant women were limited.Objective To describe the levels of maternal serum phthalate monoesters and thechanges with gestational age. To analyze the influence factors of phthalate monoestersand the relationships bewtween phthalate exposure and thyroid function. Aim to providethe information for the further population studies and experiments.Methods The present study was a part of the China-Anhui Birth Cohort Study(C-ABCS). The subjects were1492pregnant women who visited MCH centers for theirfirst prenatal examination in Ma’anshan city of Anhui Province between October2008and December2010. The participants reported information about social demographiccharacteristics, history of pregnancy and diseases, the occupational and livingenvironment and life styles. The SPE-HPLC-MS was used to detect the levels ofmaternal serum phthalate monoesters between December2011and August2013.Chi-square test and logistic regression model was applied to identify influence factorsof phthalate exposure. Pearson correlation and multiple linear regression models were used for adjusting potential confounders when examining the relationships betweenphthalate monoesters and thyroid function.Results The detection rate of monoethyl phthalate (MEP), mono-n-butyl phthalate(MBP), mono(2-ethylhexyl) phthalate (MEHP) were86.7%,99.8%and100%,respectively. The medians of corresponding phthalate monoesters were0.16ng/mL,5.97ng/mL and5.94ng/mL. The results of logistic regression showed the influencefactor of MEP was gestational age; the influence factors of MBP were gestational age,the levels of education, history of abortion, history of gynecological infections and theuse of mosquitocide in pre-pregnancy; the influence factors of MEHP were the age ofpregnant women, gestational age, residence and the use of mosquitocide inpre-pregnancy. The levels of phthalate monoesters were decline trends along with thegestational age changed. The associations among phthalate monoesters were positive bypairwise comparison. When the gestational age at5~8week, the medians ofMEP/MBP/MEHP respectively were0.19ng/mL,6.55ng/mL and8.70ng/mL, MEPwas positive correlated to MBP and MEHP (r=0.20, P<0.001; r=0.28, P<0.001), MBPwas positive correlated to MEHP (r=0.35, P<0.001); when the gestational age at9~12week, the medians of MEP/MBP/MEHP respectively were0.15ng/mL,5.75ng/mL and5.94ng/mL, MEP was positive correlated to MBP and MEHP (r=0.12, P<0.01; r=0.14,P<0.001), MBP was positive correlated to MEHP (r=0.26, P<0.001); when thegestational age≥13week, the medians of MEP/MBP/MEHP respectively were0.17ng/mL,5.90ng/mL and5.11ng/mL, MEP was positive correlated to MBP and MEHP(r=0.15, P<0.001; r=0.10, P<0.05), MBP was positive correlated to MEHP (r=0.33,P<0.001). In the different gestational age groups, MBP and MEHP was negativecorrelated to the total thyroxine, the correlations had statistical significance. In themultiple linear regression model, after adjusting for the potential confounders, theregression coefficients were-0.20(95%CI:-0.043~0.002; P=0.079),-0.032(95%CI:-0.049~-0.014; P<0.001) and-0.026(95%CI:-0.045~-0.008; P<0.01) for MBP and-0.030(95%CI:-0.054~-0.005; P<0.05),-0.042(95%CI:-0.062~-0.022; P<0.001) and -0.044(95%CI:-0.066~-0.021; P<0.001) for MEHP, respectively, at5~8week,9~12week and≥13week of gestational age. The changes of TT4with quintiles ofMBP/MEHP were declining trends.Conclusion The pregnant women were widely exposure to phthalates. The levels ofphthalate monoesters were decline trends along with the gestational age changed. In thedifferent gestational age groups, the infulence factors of phthalate monoesters weredifferent. It is needed to pay more attention to the relationships between phthalatemonoesters and the history of advers pregnancy or the use of household chemical. Theuse of plastic products should be reduced in pregnant women. The levels of phthalatemonoesters were negtively associated with TT4. The research results would provide thebasic information to evaluate environmental chemicals and the effects. But the detailedways of exposure and merchanisms of effects needed more cooperative studies.MeSH Endocrine Disruptors/Pregnancy Trimester, First/Pregnancy Trimester,Second/Pregnant Women/Phthalic Acids/Dibutyl Phthalate/Diethylhexyl Phthalate/Environmental Exposure/Maternal Exposure/Risk Factors/Thyroxine/Thyrotropin...