IVF outcome is optimized when embryos are replaced between 5 and 15 mm from the fundal endometrial surface: a prospective analysis on 1184 IVF cycles

Abstract

BackgroundSome data suggest that the results of human in vitro fertilization (IVF) may be affected by the site of the uterine cavity where embryos are released. It is not yet clear if there is an optimal range of embryo-fundus distance (EFD) within which embryos should be transferred to optimize IVF outcome.MethodsThe present study included 1184 patients undergoing a blind, clinical-touch ET of 1–2 fresh embryos loaded in a soft catheter with a low amount of culture medium. We measured the EFD using transvaginal US performed immediately after ET, with the aim to assess (a) if EFD affects pregnancy and implantation rates, and (b) if an optimal EFD range can be identified.ResultsDespite comparable patients’ clinical characteristics, embryo morphological quality, and endometrial thickness, an EFD between 5 and 15 mm allowed to obtain significantly higher pregnancy and implantation rates than an EFD above 15 mm. The abortion rate was much higher (although not significantly) when EFD was below 5 mm than when it was between 5 and 15 mm. Combined together, these results produced an overall higher ongoing pregnancy rate in the group of patients whose embryos were released between 5 and 15 mm from the fundal endometrial surface.ConclusionsThe site at which embryos are released affects IVF outcome and an optimal EFD range exists; this observations suggest that US-guided ET could be advantageous vs. clinical-touch ET, as it allows to be more accurate in releasing embryos within the optimal EFD range.

Endometrial pattern, but not endometrial thickness, affects implantation rates in euploid embryo transfers

“…Improved clinical outcomes have been demonstrated with particular stimulation protocols (1,2), embryo handling and culture conditions (3), technical factors, such as the use of the transfer catheter and placement of the embryo during ET, (4–9) and embryo selection techniques (10,11). However, identification of clinical markers of endometrial receptivity for optimization during COH remains a challenge.…”

Prospective Randomized Trial Comparing Embryo Transfers of Cases with and without Catheter Rotation during Its Withdrawal

“…Some of these proposed factors include characteristics of the catheter [1], operator experience [2], the site of uterine cavity where the embryo is transferred [3-6], presence of mucus or blood on the catheter following withdrawal [7], uterine contractions secondary to uterine manipulations, and difficulty passing through the cervix [8, 9]. …”

Embryo Transfer with Controlled Injection Speed to Increase Pregnancy Rates: A Randomized Controlled Trial

“…Most recently, Cenksoy et al [17] reported that the optimal position of the air bubble seems to be a distance of <10 mm from the endometrial fundus, in accordance with Friedman et al [34]. Rovei et al [22] concluded that the embryo(s) must be replaced between 5 and 15 mm from the endometrial fundus. This is in line with previous results from our study group - the position of the transfer air bubbles after embryo transfer closer to the endometrial fundus resulted in higher pregnancy rates [24].…”

“…Despite its relevance, the technique used in embryo transfer has received little attention and progress until recent years [2,3]. Several studies [13,17,18,19,20,21,22,23] have demonstrated that the depth of the embryo placement into the uterine cavity, as a result of the embryo transfer technique, should be considered an important factor concerning pregnancy rates. Our research group pointed out that despite standardization of the transfer by protocol, the final position of the transferred air bubbles including the embryo(s) was not accurately predictable because of dependency of the injection speed which depends on the force used to press the plunger, the resistance of the plunger and a possible uterine resistance during transfer [24].…”