Embryo transfer in IVF: Evidence-based clinical practice

Abstract

Since the first pregnancy using in vitro fertilization (IVF) was achieved nearly 30 years ago, many aspects of this procedure have undergone significant progress. In contrast, the technique of embryo transfer (ET) has remained relatively unchanged. A simple yet critical element in the final step of IVF, embryo transfer, has received little attention until recently. As poor implantation rates have increasingly hindered the growing success of IVF, the procedure of embryo transfer is now under great scrutiny. While poor embryo quality or suboptimal uterine receptivity may be responsible for implantation failures, the transfer technique itself is now also recognized as an important determinant of IVF success. Optimizing the technique of embryo transfer should take several factors into consideration. In general, the procedure starts by placing a speculum in the vagina to visualize the cervix, which is cleansed with saline solution or culture media. Additional mucus in the cervical canal can be aspirated using a sterile syringe. A transfer catheter is loaded with the embryos and handed to the clinician after confirmation of the patient's identity. The catheter is inserted through the cervical canal and advanced into the uterine cavity where the embryos are deposited. The catheter is then withdrawn and handed to the embryologist who inspects it for retained embryos. The ultimate goal of a successful embryo transfer is to deliver the embryos atraumatically to a location in the uterus where implantation is maximized. Potential reasons for a failed transfer include disruption of the endometrium by the catheter, induction of uterine contractions, deposition of the embryos in a suboptimal location, or damage to the embryos during the process. Numerous technical aspects of this procedure have been studied to minimize these complications and determine their effect on pregnancy outcome. Though much of the published data that evaluate these factors are conflicting or are confounded by variables in the IVF process that are difficult to hold constant, several aspects of the procedure warrant consideration. © Springer Science+Business Media, LLC 2010.