Embryo transfer : does ultrasound guidance make a difference ?

Ever since the birth of the first in-vitro fertilization (IVF) baby in 1978 (1), the advancement in ovulation stimulation regimes, oocyte collection and culture mediums has been phenomenal. However, the technique of uterine embryo transfer remains largely unchanged, since it was first described. The vast majority of transferred embryos fails to implant in spite of improvements in ovulation induction, fertilization and embryo cleavage. On average, up to 90% of apparently healthy zygotes transferred in utero are destined to vanish, giving no signs of trophoblastic attachment and production of human chorionic gonadotrophin (HCG) (2). Though factors relating to the embryo itself (quality, aneuploidy etc), hostile uterine environment (e.g. reflux of hydrosalpinx), inadequate endometrial development or uterine cavity anomalies and uterine contractions contribute to this failure, definitely the technique itself contributes to loss of some potentially favorable embryos for implantation. The wide variability between clinicians working in the same center (which to an extent nullifies the potential difference in the laboratory circumstances) clearly demonstrates the role of the clinician in embryo transfer and the magnitude of problem. The technique of embryo transfer that was used for long time was the clinical touch. It simply means that you feel the internal os and then either you advance the catheter till the fundus is felt and withdraw the catheter for 1 or 2 cm and position the embryos. Alternatively the clinician advances the inner catheter after feeling the resistance of the internal os by 3-4 cm based on previous measurement of the uterine cavity, Woolcott and Stanger studied 121 consecutive transvaginal ultrasound-guided embryo transfers (3). Observation was made of the guiding cannula and transfer catheter placement in relation to the endometrial surface and uterine fundus during embryo transfer. They concluded that tactile assessment of embryo transfer catheter placement was unreliable since, in 17.4% of transfers, the outer guiding catheter inadvertently abutted the fundal endometrium, the outer guiding cannula indented the endometrium in 24.8% and the transfer catheter embedded in the endometrium in 33.1%. Unavoidable sub-endometrial transfers occurred in 22.3% and avoided accidental tubal transfer in 7.4%. The possible use of US guidance to facilitate embryo transfer was first reported by Strickler et al (4), and shortly afterwards by Leong et al., (5). However the technique did not gain popularity till the last few years where several reports have claimed improved pregnancy rate after adoption of ultrasound guided transfer (6, 7).