title: The influence of the depth of embryo replacement into the uterine cavity on implantation rates after IVF: a controlled, ultrasound-guided study.
abstract: BACKGROUND
  Traditionally, embryo transfer after IVF has been performed blindly and placing the embryos approximately 1 cm below the fundal endometrial surface. However, it has been suggested that transferring embryos rather lower in the uterine cavity or high in the uterus may improve implantation rates. Nevertheless, there has not yet been a controlled trial to prove this theory. This prospective randomized study investigates the influence of the depth of embryo replacement on the implantation rate after embryo transfer carried out under transabdominal ultrasound guidance.
  
  
  METHODS
  A total of 180 consecutive patients undergoing ultrasound-guided embryo transfer were randomized to three study groups according to the distance between the tip of the catheter and the uterine fundus at the moment of the embryo deposition in the lumen of the endometrial cavity: group 1: 10 +/- 1.5 mm; group 2: 15 +/- 1.5 mm; group 3: 20 +/- 1.5 mm.
  
  
  RESULTS
  There was equal distribution between all three study groups regarding the main demographic and baseline characteristics of the patients, ovarian response, oocyte retrieval and IVF outcome, as well as the characteristics of embryo transfer and luteal phase support. The position of the catheter tip in relation to the fundal endometrial surface in groups 1 (10.2 +/- 0.9 mm), 2 (14.6 +/- 0.7 mm) and 3 (19.3 +/- 0.8 mm) was significantly different. Implantation rate was significantly higher (P < 0.05) in groups 2 (31.3%) and 3 (33.3%) compared with group 1 (20.6%).
  
  
  CONCLUSIONS
  The depth of the embryo replacement into the uterine cavity may influence implantation rates, and thus it should be considered as an additional procedure among factors recently proposed as associated with successful embryo transfer after IVF.
authors.affiliation: Service of Reproductive Medicine, Department of Obstetrics and Gynaecology, Institut Universitari Dexeus, Barcelona, Spain. vencor@iudexeus.uab.es
authors.forename: Buenaventura
authors.initials: B
authors.lastname: Coroleu
authors.forename: Pedro N
authors.initials: PN
authors.lastname: Barri
authors.forename: Olga
authors.initials: O
authors.lastname: Carreras
authors.forename: Francisca
authors.initials: F
authors.lastname: Martínez
authors.forename: Mónica
authors.initials: M
authors.lastname: Parriego
authors.forename: Lourdes
authors.initials: L
authors.lastname: Hereter
authors.forename: Nuria
authors.initials: N
authors.lastname: Parera
authors.forename: Anna
authors.initials: A
authors.lastname: Veiga
authors.forename: Juan
authors.initials: J
authors.lastname: Balasch
mesh_terms: D000328:Adult; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011446:Prospective Studies; D014463:Ultrasonography; D014599:Uterus / Q000000981:diagnostic imaging*