Hum. Reprod. Advance Access originally published online on June 4, 2009
Human Reproduction 2009 24(9):2086-2092; doi:10.1093/humrep/dep206
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Retrieval of trophoblast cells from the cervical canal for prediction of abnormal pregnancy: a pilot study
1 Department of Obstetrics & Gynecology, Wayne State University School of Medicine, Detroit, MI, USA 2 Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, MD, USA 3 Program in Reproductive and Adult Endocrinology, NICHD, NIH, DHHS, Bethesda, MD, USA
4 Correspondence address. Mott Center for Human Growth & Development, Department of Obstetrics and Gynecology, Wayne State University School of Medicine, 275 East Hancock Avenue, Detroit, MI 48201-1405, USA. Tel: +1-313-577-1748; Fax: +1-313-577-8554; E-mail: D.Armant{at}wayne.edu
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 
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.
Key words: trophoblast/cervix/first trimester/ectopic pregnancy/blighted ovum
Submitted on December 8, 2008; resubmitted on April 6, 2009; accepted on May 7, 2009.