The Association Between Levels Of Serum Bisphenol A And Thyroid Function In Pregnant Women

Background Studies about serum bisphenol A(BPA) and thyroid function of pregnant were still poorly understood, especially in China. Thyroid hormone was particularly important for fetal growth and brain development. Due to the fetus in early pregnancy entirely depends on maternal by transplacental transfer and the balance of thyroid hormone in the second or third trimester of pregnancy can promot the fetal development. Therefore, we should pay enough attention for the hazard of BPA exposure on pregnant and fetus. Because of basing on a large sample of birth cohort, the result was more reliability.Objective Understanding the distribution characteristics and influence factors of serum BPA level of pregnant women in Ma’anshan city, Anhui province. Analyzing the influence factors of serum BPA level during pregnancy and investigating the association between maternal BPA with thyroid function. To provide theoretical and experimental basis for the further clarify related research conclusions.Methods Our study was one part of the China-Anhui Birth Cohort Study(C-ABCS). 2452 pregnant women were selected from the study population of Maanshan City, and we chosed them to do the questionnaire survey from November 2008 to October 2010 in Maanshan City, Anhui Province. After Voluntarily signing the informed consent, we collection the information of social demographics, life and pregnancy related behaviors, usage of household chemical before pregnancy and food frequency during ealy pregnancy and others by self-compiled “ The maternal mother and infant health record”. At the same time, laboratory professional medical staff collected peripheral blood of pregnant women in the fasting state, and the capacity of sample was about 5m L. After collecting, we centrifuged the blood samples and then cryopreservation at the refrigerator of-80 degree centigrade. Maternal serum thyroid hormone(TH) and thyroid stimulating hormone(TSH) were detected by the automatic chemiluminescence immune apparatus in November 2010 at the First Affiliated Hospital of Anhui Medical University laboratory. Double data entering through the Epi Data3.0 and inspecting database by consistency check. After merging databases through SPSS13.0 statistical software, we got rid of pregnant women who were lost to follow-up(that was no basic information during ealy pregnancy) and intaked 2 414 pregnant women as the research object. Using the percentile method to describe sociodemographic characteristics, life or gestational age related behavior and distribution of serum BPA during pregnancy. Whereafter, there were 2 150 pregnant women ultimately included in the study after excluding pregnant women of twins, suffering from thyroid or other metabolic diseases and being not detected due to insufficient blood. Chi-square test was used to analy the factors affecting maternal BPA exposure. The analysis of variance(ANOVA) was used to know the influence foctors of serum TH during pregnancy. Finally, we used the multiple linear regression for the correlation analysis between maternal serum BPA and TH and TSH levels.Results The detection rate of maternal serum BPA in our study was 82.4%, and median were 0.21ng/m L, and its concentration ranging from not detected to 21.65ng/m L. The overall level was positively skewed distribution. Multivariate linear regression analysis was used to analyze the association between maternal serum BPA and thyroid hormone. After controlling for the covariates(factors which related with BPA and outcome variable and statistical significance in the chi-square test and ANOVA results), the association between maternal serum BPA with TT4, FT4 and TSH was only found in the 9-12 weeks of gestation. Maternal serum BPA was negative correlation with TT4 and FT4(β=-0.013, 95%CI:-0.019~-0.006; β=-0.008, 95%CI:-0.014~-0.002), and positive correlation with TSH(β= 0.044, 95%CI: 0.001~-0.087).Conclusion Pregant women were widely exposed to BPA during pregnancy, and the effect of serum BPA levels in different trimester on thyroid hormone were also exist differences. Maternal serum BPA was negative correlation with TT4 and FT4, and positive correlation with TSH in the second half of the early stages of pregnancy(9-12 weeks of gestation). Considering the abnormal changement of TH(TSH) level in pregnancy(especially in early pregnant) may be harmful to the normal growth and brain development of fetus, so we shoud focus on the correlation research.