| The first part:Preconception TSH and risk factors in Chinese married women planning conceptionBackgrounds and ObjectivesThe impact of thyroid disease on pregnancy has been an area of increasing research attention over the last two decades. Thyroid dysfunction during pregnancy has been associated with adverse maternal and fetal outcomes, including miscarriage, delivery, excessive fetal growth and neonatal neuropsychological development deficiency. In addition, women who have been exposed to thyroid dysfunction during pregnancy are at an exceptionally high risk of diabetes and thyroid disease later in life. So far, many correlated studies focus on the thyroid dysfunction during pregnancy. However, the preconception thyroid dysfunction is seldom dealt among these studies. Thyroid stimulating hormone (TSH) is regarded as the most sensitive criteria in reflecting thyroid dysfunction. Therefore, we conducted this study to investigate the distribution of TSH in Chinese married women who prepare for pregnancy, and further discuss the risk factors associated with abnormal preconception TSH.Subjects and MethodsPreconception TSH data were drawn from the National Free Pre-pregnancy Checkups in 2013.1.1-2013.12.31. Two different reference ranges of TSH were used to judge abnormal preconception TSH level:one is the reference ranges of TSH test kits, and the other is the specific reference range in early pregnancy suggested by America Thyroid Association (ATA) in 2011. In addition, the impact of age, body mass index (BMI), history of adverse pregnant outcome, hypertension, hemoglobin concentration and fasting blood glucose levels on abnormal TSH level before pregnancy were further examined.ResultsA total of 397304 women were included in the present study. The median of preconception TSH was 1.73 mIU/L The proportion of smaller than TSH reference range, greater than TSH reference range, smaller than 0.1 mIU/L and greater than 2.5 mIU/L was 2.54%,3.34%,0.93% and 26.56%, respectively. In multivariate logistic regression analysis, age, BMI and fasting blood glucose levels was positively correlated with rised TSH risk. And there was a type U correlation between hemoglobin concentration and rised TSH risk. Besides, hypertension and history of adverse pregnant outcome were also risk factors of abnormal preconception TSH.ConclusionsThe prevalence of abnormal TSH in reproductive-aged women wishing to conceive differs from each other according to two kinds of TSH reference ranges recommended by ATA and TSH detection kits. Hence, scientific standard TSH reference range specific to women preparing for pregnancy should be established and the screening for thyroid function should be strengthened.The second part:Thyroid antibodies and gestational diabetes mellitus:a meta-analysisBackgrounds and ObjectivesGestational diabetes mellitus (GDM) is one of the most common pregnancy complications associated with a number of adverse outcomes, including miscarriage, delivery, excessive fetal growth, birth trauma and neonatal metabolic abnormalities. In addition, women who have been exposed to GDM during pregnancy are at an exceptionally high risk of developing type 2 diabetes, chronic hypertension and vascular disease later in life. In recent years, many epidemiological studies have investigated the links between thyroid antibodies, including thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) and risk of GDM. However, these studies have apparently yielded conflicting results. Therefore, to clarify the evidence, we conducted a meta-analysis of available case-control and cohort studies of thyroid antibodies and GDM.Subjects and MethodsTo study the association between thyroid antibodies (TPOAb or TgAb) and GDM, an electronic search was conducted using PubMed and two Chinese databases, Wanfang and China National Knowledge Internet (CNKI), from inception to October 2014. All of the literature searches were reviewed independently by two authors. The fixed-effects model was used to pool the results. In addition, subgroup analyses were conducted stratifying by the type of study design, type of thyroid antibody (TPOAb or TgAb) and thyroid dysfunction exclusions. Publication bias was assessed using funnel plots and the Egger regression test. We conducted all analyses using Stata software, version 12.0.ResultsThe search strategy identified 167 potentially relevant publications, of which 20 were included in the meta-analysis. A significant association between thyroid antibodies and GDM was observed with a pooled RR of 1.12 (95%CI 1.03-1.22). A meta-analysis of the 11 cohort studies with pregnant women with positive thyroid antibodies in their first trimester suggested no obvious risk of GDM compared with the reference group (pooled RR=1.07,95%CI 0.96-1.19). In subgroup meta-analyses, no significant association between thyroid antibodies and GDM was found in euthyroid pregnant women (pooled RR=1.08,95%CI 0.97-1.22), whereas a significant positive association was identified in women with a thyroid dysfunction (pooled RR=1.35,95%CI 1.06-1.71).ConclusionsBased on the currently available evidence, there is a significant but not strong association between thyroid antibodies and the risk of GDM, and thyroid antibodies in the first trimester lack a predictive value for the risk of GDM. In addition, thyroid antibodies may not increase the risk of GDM in euthyroid pregnant women. |
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