Prospective Randomized Controlled Trial Comparing Two Different Embryo Transfer (ET) Catheters

Introduction

Embryo transfer (ET) is the final and critical step in the long pathway of in vitro fertilization (IVF) treatment. Implantation is a complex process and, as yet, one not fully understood. Aside from the quality of the embryos replaced and the receptivity of the endometrium, the embryo transfer procedure itself might impact the implantation process.

The procedure has changed very little since the first descriptions. Numerous data suggest that difficult transfers should be avoided, as they are likely to reduce the chances of implantation and subsequent pregnancy rates.

It has been proposed on the basis of small studies that traumatic embryo transfer can induce uterine contractions capable of displacing the embryo or induce unwanted endometrial damage. The evidence is unclear, however, as whilst several studies support this concept, others do not.

Free hand embryo transfer with soft catheters under ultrasound guidance is considered the best option in transferring embryos. Many retrospective trials have reported higher Pregnancy Rates (PR) with soft catheters compared with hard catheters. However in technically difficult ET, where difficulties are met in negotiating the cervical os, the use of harder catheters is needed. The change from soft to hard catheters in these transfers, along with the difficulty of the transfer itself, may account for differences in pregnancy rate.