© Springer India 2015
Gautam N. Allahbadia and Claudio F. Chillik (eds.)Human Embryo Transfer10.1007/978-81-322-1115-0_22. Trial Embryo Transfer (Mock Transfer)
(1)
Department of Obstetrics and Gynecology, University of California, San Francisco-Fresno, Fresno, CA, USA
(2)
Department of Reproductive Medicine, Center for Studies in Genetics and Reproduction (CEGYR), Buenos Aires, Argentina
(3)
Department of Assisted Reproduction, Center for Studies in Genetics and Reproduction (CEGYR), Buenos Aires, Argentina
Abstract
Mock transfer is an important part of the in vitro fertilization (IVF) procedure; it can be easily done during the cycle before the procedure and will collect valuable information for when the actual embryo transfer takes place. Knowing the length of the uterine cavity, its orientation and, above all, how easy it is to pass the endocervical canal should help in doing an easy transfer when the time comes. Avoiding the use of a tenaculum, laminaria or cervical dilators should optimize the success of assisted reproductive technology (ART) procedures, as the incidence of uterine contractions and blood in the catheter is significantly decreased.
Keywords
Mock transferLaminariaTenaculumStyletIntroduction
In vitro fertilization (IVF) has become the most effective tool for the treatment of human infertility, with over five million births worldwide. Since the pioneering years of IVF, many changes have been introduced, all geared towards improving the pregnancy rates that we can offer our patients. The impact of these changes has been significant, especially in the so-called good prognosis IVF patients, in which clinical pregnancy rates over 50 % are not unusual today. It is worth mentioning that today, the IVF laboratory is functioning with great predictability, systematically culturing and making available high-quality blastocysts that carry a high rate of implantation.
Transferring embryos transcervically was traditionally considered a simple technical procedure, and no major changes have taken place since it was first introduced three decades ago by Edwards et al. [1]. Yet, it is fair to say that complicated or difficult embryo transfers (ETs) are not uncommon and can ruin many days of hard work in the IVF laboratory, compromising a couple’s chance of achieving pregnancy.
Clinicians typically describe the embryo transfer procedures as easy or difficult, reflecting the technical problems that one may encounter in trying to pass the embryo transfer catheter through the cervical canal and into the uterine cavity, where the embryo or embryos are going to be placed. Englert et al. [2] reported a 33.3 % clinical pregnancy rate with embryo transfers rated as excellent, while in difficult cases, the pregnancy rate was only 10.5 %.
There are many factors that may be associated with a difficult embryo transfer. Sometimes, the challenges are anatomical in nature, reflecting the presence of ridges or folds in the cervical canal, while at other times, they may be due to variations in the cervical-uterine body axis and/or uterine position. Whatever the existing problem might be, there is consensus that a complicated embryo transfer typically, is associated with a lower pregnancy rate, in comparison to the pregnancy rate expected, based on the patient’s age, embryo quality, etc.
When and How to Do It
The trial embryo transfer, or mock transfer, is a procedure typically performed in the month before the actual IVF cycle, with the objective of evaluating the passage of a transfer catheter into the uterus, as well as to establish the length of the cavity, from the external cervical os to the uterine fundus. It documents the position of the uterus (anteverted, retroverted, etc.) and is later used as a reference during the actual embryo transfer, with the objective of avoiding any possible complications that may hinder a patient’s chance for success.
The goal of a successful ET is to deliver the embryos atraumatically to a location in the uterus where implantation is maximized [3]. Potential reasons for failing to accomplish that may be due to a disruption of the endometrium by the transfer catheter itself, as demonstrated by our group [4]. We clearly showed that soft catheters are less traumatic to the endometrial tissue, by performing diagnostic hysteroscopies after mock transfers with different catheter types. However, there are multiple other reasons for a difficult ET, among which, the dexterity and experience of the operator is felt to be an important factor, with reports showing that a minimum number of transfers are needed before a clinician shows competency in performing ETs [5].
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