Location of the embryo-transfer catheter guide before the internal uterine os improves the outcome of in vitro fertilization

The objective of this study was to assess whether positioning the embryo transfer (ET) catheter guide at the time of embryo expulsion, before or beyond the internal os, has an impact on IVF cycle outcome. We performed a retrospective study comparing IVF outcomes in relation to the ET guide position relative to the internal uterine os. We analyzed ultrasound-guided ETs in IVF-intracytoplasmic sperm injection (ICSI) cycles, performed with the tip of the ET catheter guide just before the internal os (group 1) and beyond the internal os (group 2). Implantation and pregnancy rates were significantly better in group 1 than in group 2, at 14.8% versus 11.8% and 57.3% versus 43.1, respectively. We conclude that passing the ET catheter guide beyond the internal os reduces implantation and pregnancy rates.