title: Retrieval of trophoblast cells from the cervical canal for prediction of abnormal pregnancy: a pilot study.
abstract: BACKGROUND
  Fetal cells are shed from the regressing chorionic villi and it is possible to retrieve extravillous cytotrophoblast cells by transcervical sampling. The abundance of trophoblast cells in transcervical samples suggests that this non-invasive approach could distinguish between normal and abnormal pregnancies, such as an ectopic pregnancy (EP) and blighted ovum (BO). We aim to identify and quantify fetal trophoblast cells in the cervical canal during the first trimester to assess their usefulness to predict an abnormal pregnancy.
  
  
  METHODS
  Patients, age 18-45, presenting with a normal intrauterine pregnancy (IUP; n = 37), diagnosis of EP (n = 10) or BO (n = 5) were enrolled for collection of transcervical specimens using a cytobrush and fixative rinse. Non-pregnant, nulliparous women (n = 7) were included as negative controls. Cells were cleared of mucus by acidification, prepared on microscope slides and labeled with a monoclonal antibody recognizing the trophoblast marker, human leukocyte antigen (HLA)-G. HLA-G positive and negative cells were counted to calculate the ratio of trophoblast cells to total cervical cells.
  
  
  RESULTS
  Trophoblast cells were observed in 35/37 normal IUP, 6/10 EP and 4/5 BO specimens. The average frequency of HLA-G positive cells in the normal IUP cervical samples was approximately 1 in 2000, which was 4-fold higher than samples from patients with EP or BO (P < 0.001). Receiver operating characteristic analysis showed that EP and BO pregnancies were distinguishable from normal pregnancies with 93% sensitivity, 95% specificity, 97% positive predictive value and 87% negative predictive value.
  
  
  CONCLUSIONS
  This pilot study presents evidence that trophoblast cells can be reliably obtained and identified among cervical cells in the first trimester by immunohistochemical staining for HLA-G, and suggests for the first time that abnormal pregnancies may be predictable based on the abundance of trophoblast cells in the cervical canal.
authors.affiliation: Department of Obstetrics & Gynecology, Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Imudia
authors.forename: Yoko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Brian A
authors.initials: BA
authors.lastname: Kilburn
authors.forename: Frank D
authors.initials: FD
authors.lastname: Yelian
authors.forename: Michael P
authors.initials: MP
authors.lastname: Diamond
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.forename: D Randall
authors.initials: DR
authors.lastname: Armant
mesh_terms: D000293:Adolescent; D000328:Adult; D002584:Cervix Uteri / Q000166:cytology*; D005260:Female; D006680:HLA Antigens / Q000032:analysis; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000032:analysis; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis* / Q000276:immunology; D011261:Pregnancy Trimester, First / Q000276:immunology; D011271:Pregnancy, Ectopic / Q000175:diagnosis / Q000276:immunology; D014327:Trophoblasts / Q000166:cytology* / Q000276:immunology
chemical_list: D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I