title: Ethnic Differences in Preterm Birth Risks for Pregnant Women with Thyroid Dysfunction or Autoimmunity: A Meta-analysis.
abstract: OBJECTIVE
  Abnormal maternal thyroid function is associated with preterm birth. However, this association stays dubious in relevant individual studies for ethnic difference reasons and lack of direct supporting data. This study aimed to evaluate the relationship between preterm birth and thyroid dysfunction or autoimmunity based on ethnic differences.
  
  
  METHODS
  Relevant studies were identified through searches of MEDLINE, Excerpta Medica, Wan Fang, China Biological Medicine disc, and China National Knowledge Infrastructure from inception to June 15, 2016. Original articles in which an incidence or prevalence of thyroid dysfunction or autoimmunity before second trimester of pregnancy could be extracted were included.
  
  
  RESULTS
  Thirty-two unique studies were included for the final meta-analysis. Patients involved were divided into two groups: Group 1 (G1) and Group 2 (G2) comprising of Asian and Caucasian populations, respectively. Positive thyroid antibodies were associated with the occurrence of preterm birth in both G1 [odds ratio (OR): 3.62, 95% confidence interval (CI): 2.83-4.65] and G2 (OR: 1.35, 95% CI: 1.17-1.56); hypothyroidism, only in G2 (OR: 1.20, CI: 1.09-1.33); and subclinical hypothyroidism or hypothyroxinemia, in neither group.
  
  
  CONCLUSIONS
  Thyroid autoimmunity may be a more favorable factor leading to preterm birth among pregnant women of different ethnicities, compared with thyroid dysfunction.
authors.affiliation: Department of Gynecology and Obstetrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Gynecology and Obstetrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Shao Wei
authors.initials: SW
authors.lastname: Wang
authors.affiliation: Department of Gynecology and Obstetrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Feng Li
authors.initials: FL
authors.lastname: Wu
authors.affiliation: Institute of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Shi
authors.affiliation: Institute of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Pu Lin
authors.initials: PL
authors.lastname: Yu
authors.affiliation: Department of Gynecology and Obstetrics, Morin Dawa Daur Autonomous Banner Hospital, Hulunbuir 162850, Inner Mongolia Autonomous Region, China.
authors.forename: Xiu Ling
authors.initials: XL
authors.lastname: Peng
authors.affiliation: Institute of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Sun
mesh_terms: D001327:Autoimmune Diseases / Q000208:ethnology* / Q000276:immunology / Q000503:physiopathology; D015551:Autoimmunity; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011248:Pregnancy Complications / Q000208:ethnology* / Q000276:immunology / Q000503:physiopathology; D047928:Premature Birth / Q000208:ethnology / Q000276:immunology / Q000503:physiopathology; D013959:Thyroid Diseases / Q000208:ethnology* / Q000276:immunology / Q000503:physiopathology; D013961:Thyroid Gland / Q000503:physiopathology
keywords: Autoimmunity; Ethnicity; Hypothyroidism; Preterm birth; Thyroid