title: The importance of the length of uterine cavity, the position of the tip of the inner catheter and the distance between the fundal endometrial surface and the air bubbles as determinants of the pregnancy rate in IVF cycles.
abstract: OBJECTIVE
  To evaluate the relationship between the pregnancy rate (PR) and the positioning of the intrauterine catheter at embryo transfer (ET) under transabdominal ultrasound (US) guidance in in vitro fertilization (IVF) cycles.
  
  
  METHODS
  Prospective data analysis of 281 consecutive US-guided fresh ETs performed by a single physician at Yeditepe University Hospital IVF Center, Istanbul, Turkey, after controlled ovarian hyperstimulation between April 2012 and March 2013. The length of the uterine cavity (A), the distance between the fundal endometrial surface and the tip of inner catheter (B), the distance between the fundal endometrial surface and the air bubbles (C), and the pregnancy rates (PRs) were recorded.
  
  
  RESULTS
  The mean age of the patients was 33.25±5.5 years. Of all transfers, 115 (40.9%) resulted in a clinical pregnancy. With regard to distance (C), the clinical intrauterine pregnancy rates were 65.2%, 32.2% and 2.6% in the <10mm, 10-20mm, and 20mm distance groups, respectively. The PR was dramatically reduced in cases with >10mm between the fundal endometrial surface and the air bubbles, although this did not reach statistical significance. Between those patients who conceived and those who did not, there was no significant difference in terms of the distance between the fundal endometrial surface and the tip of inner catheter, the ratio of A/B or the ratio of B/C.
  
  
  CONCLUSIONS
  The final position of the air bubble used as an identifier of the position of the embryo at ET can be determinative for PR, although it cannot be predicted. Clinical pregnancy rates appeared higher in cases with air bubbles closer to the fundus and the optimal position of the air bubble seems to be a distance of <10mm from the fundal endometrial surface. It could be advisable to monitor the final position of air bubble at ET for identifying PR. In addition, the depth of uterine cavity may be considered to indirectly be important factor as it affects ET depth. The optimal distance between the fundal endometrial surface and the tip of inner catheter is 1.5-2cm. Further well-designed randomized controlled trials are required to optimize ET technique in the future.
authors.affiliation: Department of Gynecology and Obstetrics, Faculty of Medicine, Yeditepe University, Devlet yolu Str., 102-104 Istanbul, Turkey. Electronic address: drpinarozcan@hotmail.com.
authors.forename: Pınar Ozcan
authors.initials: PO
authors.lastname: Cenksoy
authors.affiliation: Department of Gynecology and Obstetrics, Faculty of Medicine, Yeditepe University, Devlet yolu Str., 102-104 Istanbul, Turkey. Electronic address: cemficicioglu@gmail.com.
authors.forename: Cem
authors.initials: C
authors.lastname: Fıcıcıoglu
authors.affiliation: Department of Gynecology and Obstetrics, Faculty of Medicine, Yeditepe University, Devlet yolu Str., 102-104 Istanbul, Turkey. Electronic address: yesiladali@hotmail.com.
authors.forename: Mert
authors.initials: M
authors.lastname: Yesiladali
authors.affiliation: Department of Gynecology and Obstetrics, Faculty of Medicine, Yeditepe University, Devlet yolu Str., 102-104 Istanbul, Turkey. Electronic address: oyaalagozakcin@gmail.com.
authors.forename: Oya Alagoz
authors.initials: OA
authors.lastname: Akcin
authors.affiliation: Faculty of Medicine, Department of Medical Informatics, Yeditepe University, Devlet yolu Str., 102-104 Istanbul, Turkey. Electronic address: ecaltuok@yeditepe.edu.tr.
authors.forename: Cigdem
authors.initials: C
authors.lastname: Kaspar
mesh_terms: D000328:Adult; D002404:Catheterization / Q000379:methods; D015331:Cohort Studies; D004624:Embryo Transfer / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D018084:Ultrasonography, Interventional / Q000379:methods*; D014599:Uterus / Q000033:anatomy & histology / Q000000981:diagnostic imaging*
keywords: Embryo transfer; In vitro fertilization; Uterine length