The effect of air bubble position after blastocyst transfer on pregnancy rates in IVF cycles.

Objective: To investigate the relationship between air bubble position after blastocyst transfer (BT) and pregnancy rates (PRs).

Design: Retrospective cohort study.

Setting: University-based infertility center.

Patient(s): Three hundred fifteen consecutive nondonor BTs by a single provider.

Intervention(s): Catheters were loaded with 25 μL of culture media, 20 μL of air, 25 μL of media containing the blastocysts, 20 μL of air, and a small amount of additional media. The distance from the air bubble to the fundus, as seen on abdominal ultrasound examination, was measured at the time of transfer. Air bubble location was categorized as <10 mm, 10-20 mm, and >20 mm from the fundus.

Main Outcome Measure(s): Clinical pregnancy rate.

Result(s): After controlling for age, parity, FSH and frozen transfers, and accounting for repeated cycles per patient, the PRs for both the >20-mm (38.3%) and the 10-20-mm (42.0%) from the fundus group were significantly reduced compared with the group in which the bubble was <10 mm from the fundus (62.5%).

Conclusion(s): This study is the first to suggest that BT closer to the fundus is associated with higher PR. Although no ectopic pregnancies occurred in the <10-mm group, this outcome should be monitored closely in larger studies.