Techniques for preparation prior to embryo transfer

Embryo transfer (ET) is the final and most vulnerable step in in vitro fertilisation (IVF) treatment. Pregnancy rates after ET may be influenced by several factors, including straightening the utero-cervical angle, cervical and endometrial preparation, and techniques for traversing the cervix. Recent research has focused on improving the ET technique in the hope of increasing IVF success rates. This review, first published in 2009, examined preparation techniques, as it remains unclear whether these simple interventions make ET an easier procedure with higher success rates and fewer complications.

To assess the benefits and harms of different preparation techniques prior to ET.

We searched the Cochrane Gynaecology and Fertility Group's Specialised Register, CENTRAL, MEDLINE, Embase, and PsycINFO on 6 October 2025. We handsearched the citation lists of relevant publications, reviews, and included studies. We contacted experts in the field and searched trial registries to identify any unpublished or additional trials.

We included randomised controlled trials (RCTs) of the following interventions: straightening the utero-cervical angle (full bladder), cervical and endometrial preparation (removing mucus), and techniques for traversing the cervix (afterloading). Participants were women with any type of infertility undergoing IVF treatment and reaching the ET stage.

Our critical outcomes were live birth rate and total adverse events per woman randomised. Important outcomes included pregnancy rate, pregnancy loss rate, and difficulty of transfer.

We assessed the risk of bias in included studies independently for each result using the Cochrane RoB 2 tool.

Two or more review authors critically appraised potentially eligible studies. Two or more review authors independently extracted data, with any disagreements resolved by discussion with a third review author. Where appropriate data were available, we conducted meta-analysis; otherwise, we presented results narratively. We expressed dichotomous outcome data as a risk ratio. We planned the investigation of heterogeneity, subgroup analysis, and sensitivity analysis.

We included 11 studies (2524 women) in the review. Of these, six studies (1341 women) evaluated the effects of three key preparation techniques before embryo transfer: straightening of the utero-cervical angle, comparing full bladder with empty bladder (two studies); cervical preparation techniques versus no intervention, comparing removal of cervical mucus to no mucus removal (two studies); and techniques for traversing the cervix, comparing afterloading to direct ET under ultrasound guidance (two studies).

This review evaluated the effects of various preparation techniques on ET outcomes. The evidence is generally of low or very low certainty and therefore should be interpreted with caution. Straightening of the utero-cervical angle: ET under a full bladder versus an empty bladder No study reported the total number of live births and adverse events. We are very uncertain about the effect of a full bladder versus an empty bladder on pregnancy rate (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.69 to 1.48; I² = 0%; 2 studies, 273 participants; very low-certainty evidence), pregnancy loss rate (RR 0.96, 95% CI 0.43 to 2.14; 1 study, 131 participants; very low-certainty evidence), or difficulty of transfer (RR 0.41, 95% CI 0.16 to 1.08; 1 study, 142 participants; very low-certainty evidence). Cervical and endometrial preparation: removing mucus versus no mucus removal One study reported 52 live births per 220 cycles in the intervention group and 42 live births per 205 cycles in the control group (low-certainty evidence). No study reported the total number of adverse events. There may be little to no difference in pregnancy rate between the removing mucus group and the no mucus removal group based on one study (RR 1.02, 95% CI 0.58 to 1.80; 1 study, 97 participants), while a second study reported 65 pregnancies per 220 cycles in the intervention group and 63 pregnancies per 205 cycles in the control group (low-certainty evidence). One study reported pregnancy loss rates (15/220 cycles in the intervention group and 20/205 cycles in the control group) (low-certainty evidence). No study reported data on difficulty of transfer for this comparison. Techniques for traversing the cervix: embryo afterloading versus direct ET No study reported the total number of live births and adverse events. Embryo afterloading may result in little to no difference in pregnancy rate (RR 1.09, 95% CI 0.91 to 1.31; I² = 0%; 2 studies, 654 participants; low-certainty evidence) and pregnancy loss rate (RR 1.13, 95% CI 0.59 to 2.13; 1 study, 352 participants; low-certainty evidence). We are very uncertain about the effect on difficulty of transfer (very low-certainty evidence): one study reported that afterloading may reduce the difficulty of transfer (RR 0.25, 95% CI 0.15 to 0.41; 1 study, 352 participants), while another study reported there was no difficulty of transfer for both groups.

We added three new studies in this update, but their inclusion did not change the main conclusions of the review. No specific implications for practice are made based on the available evidence. There is a need for further and larger studies on ET preparation techniques, which should be better designed, with clearly described methods and inclusion and exclusion criteria, and greater numbers of participants.

This Cochrane review had no dedicated funding.

Protocol and previous versions available via https://doi.org/10.1002/14651858.CD007682, and https://doi.org/10.1002/14651858.CD007682.pub2.