Objective: to determine the relationship between embryo transfer outcome and the distance between fundal endometrial surface and air bubbles assessed by trans-abdominal ultrasound Design: Prospective (cohort) study Setting: This study was conducted in assisted reproductive technology (ART) unit of Ain Shams University Hospital from April 2015 to October 2016. Patient(s): Eighty two women undergoing ICSI were enrolled in and a written informed consent was obtained from each participant. Intervention(s): no patient received any additional procedure or intervention. Outcome measuers: The primary outcome was biochemical pregnancy rate based on serum beta-hCG level at 14 days after ET. Secondary outcome was clinical pregnancy rate using trans-vaginal US examination at 6 – 8 weeks of amenorrhea to detect the presence of fetal sac & pulsation. Results: Implantation, biochemical and clinical pregnancy rates were significantly higher in distance < 10 mm group than ≥ 10 mm group. Conclusion: air bubble used as an identifier of the position of the embryo at ET can be determinative for pregnancy rates. Clinical PRs were higher in cases with air bubbles < 10 mm from fundal endometrial surface.