Interpretation
CAVITY
Patients included in our 4D UGET group achieved a LBR of 41%, almost double that of the current national LBR per single ET of 24%Previous studies using 2D ultrasound proposed the best embryo deposition point to lie within 0.5–2 cm from the fundus of the uterine cavity, which is further endorsed by recent reviews with recommended deposition in the upper/middle third of the uterine cavity (between 1 and 2 cm from the fundus)Variances in uterine cavity shape of 4 patients included in the trial highlighting the importance of a patient specific approach. Echobright areas show embryo deposition.Although there is a dearth of available evidence for 4D UGET, a number of previous studies have highlighted the benefit of obtaining 3D views of the endometrial cavity during ETThe largest 4D UGET study to date, reported by Gergely and colleagues was a retrospective observational study, and the authors found an increase in pregnancy rate of 10% compared with 2D UGET when 3D/4D ultrasound guidance was implementedThere are many postulated benefits of 4D UGET, which include improved patient experience and comfort. However, this was not reflected in the patient satisfaction/comfort scores, presumably due to a large proportion of the women not having experienced any other form of transfer. However, the large number of positive responses in the free text comments did convey appreciation towards the 4D UGET approach. These comments included improved comfort/satisfaction due to reduced duration of speculum insertion, being able to have an empty bladder and the reassurance of being able to see the transfer on the ultrasound screen.No difference between the groups regarding the difficultly of ET was noted but all 4D UGET procedures were performed by the same experienced individual (LN). More conversions to 2D UGET were noted in the 4D UGET group, predominately due to suboptimal views in patients with an axial or thin endometrium. We are aware that inherent subjective bias could influence these results, therefore in a future study multiple practitioners should perform the two ET techniques that are compared. Although the 4D UGET did take a significantly longer time to perform and this could be at the detriment to a busy ET list, we feel the positive responses with regards to the 4D UGET would serve as justification to the small increase in length of procedure.