Microdrop in utero movements after embryo transfer

Introduction: Embryo transfer (ET) techniques and modifications have been extensively studied recently as one the main variables affecting in vitro fertilization (IVF) pregnancy rates; many of ET independent variables have been studied with discordant results: A better understanding of endometrial movements could help improve ET efficiency and IVF success. Objectives: The aim of this study was to record and study microdrop in utero movements after ET by ultrasound (US). Materials and Methods: 18 patients underwent pelvic US for 4 h following ET, at 15 min intervals. ET occurred on day + 3 of embryo development following IVF stimulation. The microdrop that contained the embryos consisted of 25 ΅L of culture media and was randomly placed 1-3 cm from the fundus. Results: The microdrop could be seen leaving the catheter and deposited in the final 3 cm of the uterine cavity. In the following US, endometrial wave movements flowing from the cervix to fundus and fundus to cervix could clearly be seen, and these waves started at both ends simultaneously. The microdrop moved from the fundus to about 1 cm from the isthmus, and back again. There were times when it was virtually stationary. In all cases, after 1 h the microdrop had moved from its original position. The intensity of the endometrial movements was different in every patient. Discussion: The endometrial waves that start immediately after ET probably serve to keep the embryo within the uterine cavity, and to select the most appropriate place for implantation. This study shows for the first time microdrop movements after ET. Given this endometrial activity, we should not be concerned about positioning the embryo correctly at transfer as simply ensuring the catheter is within the uterine cavity should be enough, avoiding endometrial damage.