![]() Thirty individuals with no blood drawn were excluded. No women were included in more than one trimester.įrom June 2011 to September 2012, a total of 381 pregnant women undergoing their 1 st trimester prenatal screening in their 9 th–13 th week of pregnancy were included in the sequential group. For each woman, all data used in this study relate only to a single set of results from blood collected at their visit to the antenatal clinic. Eligible pregnant women who consented to enroll in the study had blood collected when presenting to the antenatal clinic. The study area (Shanghai) is an iodine-stable and adequate area, and the median level of urinary iodine in the population is 231.01 μg/L.įrom February 2011 to June 2011, a total of 447 pregnant women were enrolled in the nonsequential group, including 140 patients in their 9 th–13 th week of pregnancy (1 st trimester ), 184 in their 16 th–20 th week of pregnancy (2 nd trimester ), and 123 in their 37 th–40 th week of pregnancy (3 rd trimester ). According to the recommendations of the National Academy of Clinical Biochemistry (NACB) for determining TFT reference intervals, the inclusion criteria were as follows: single birth Han Chinese women no history of thyropathy or autoimmune disease no goiter thyroid peroxidase antibody (TPOAb) negative and no use of medicine affecting the thyroid hormone. The study group consisted of pregnant women undergoing their trimester prenatal screenings at the International Peace Maternity and Child Health Hospital. Written informed consent was obtained from each subject before sample collection. Ethical approval for this project was granted by the Ethics Committee of the International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University. This study was performed in accordance with the relevant guidelines and regulations. ![]() In this study, we aimed to establish a gestation-specific reference interval for TFTs by analyzing data derived from a Chinese population of pregnant women, and we compared the nonsequential and sequential methods for the evaluation of maternal thyroid function. However, few studies have been performed to deciding more stable and reasonable method for establishing reference intervals. There are two methods of blood sample collection, the nonsequential and sequential methods. Correct establishment of reference intervals will directly affect the accuracy of disease diagnosis, and the TSH upper limit and the FT4 lower limit play key roles in the diagnosis of clinical/subclinical hypothyroidism or hypothyroxinemia. Therefore, the International Federation of Clinical Chemistry and the International Committee for Standardization Hematology recommend that each laboratory should establish its own reference range. One study examining a mixed ethnic population of pregnant women in the United Arab Emirates (UAE) showed that free thyroxine (FT4) levels differ significantly between UAE nationals and Asians during the 1 st and 2 nd trimesters while there was no significant difference in thyroid stimulating hormone (TSH) levels between the various ethnic groups. Recently, a number of studies on the establishment of gestation-specific reference intervals have been published however, these reference intervals varied due to regional and ethnic differences and due to the different detection methods and kits used. Thus, it is important to establish gestation-specific reference intervals for thyroid function tests (TFTs) during pregnancy. This can lead to the overdiagnosis of hyperthyroidism and misdiagnosis of hypothyroidism with nongestation-specific reference intervals. Thyroid gland physiology changes during pregnancy because of the effects of increased levels of thyroid-binding globulin and human chorionic gonadotropin and enhanced iodine metabolism. However, only 30–80% of women with hypothyroidism are identified by screening based on symptoms/risk factors. Given the prevalence and adverse outcomes related to maternal thyroid dysfunction, a considerable number of studies have been conducted in the past few years that focused on improving pregnancy outcomes by screening pregnant women for thyroid disease. ![]() For example, human maternal thyroid hormones are important for fetal brain development, and low concentrations of thyroid hormones in patients with hypothyroidism during early pregnancy can be potentially damaging to the neurodevelopment of the fetus. Maternal thyroid dysfunction is common during pregnancy and may be associated with many adverse outcomes in both the mother and the fetus. During pregnancy, thyroid physiology often exhibits large changes due to the influence of varying hormone levels.
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