The Hull IVF Unit, The Princess Royal Hospital, Saltshouse Road, Hull HU8 9HE, UK
Dear Sir,
We read with much interest a recent paper by Prapas et al. regarding ultrasound-guided embryo transfer (Prapas et al., 2001). In this paper pregnancy rates after ultrasound-guided embryo transfer were compared with the tactile assessment (clinical feel) method on days 3, 4 and 5 after oocyte retrieval. The ultrasound-guided procedure yielded a significantly higher overall pregnancy rate after embryo transfer on days 3 and 4, but not on day 5 and this difference was explained by a provoked asynchrony between embryo stage and endometrial phase, which could occur on day 3 and day 4, but not on day 5, when no asynchrony can be provoked. We propose that the results of this study can also be explained by the effect of progesterone on uterine contractions.
Uterine contractions at the time of embryo transfer have been associated with markedly lower implantation and pregnancy rates per embryo transfer (Fanchin et al., 1998) and our unit has shown that touching the uterine fundus during embryo transfer can provoke uterine contractions, which consequently would reduce the success rate (Lesny et al., 1998
). The risk of touching the uterine fundus is increased with the clinical feel method as compared with the ultrasound-guided procedure and therefore a higher frequency of uterine contractions can be expected after the clinical feel method. The negative effect of this can be seen on day 3 and 4 embryo transfers, when a significantly decreased pregnancy rate is seen after the clinical touch method as compared with the ultrasound-guided method. However from days 47 a pronounced decrease in uterine contractions occurs (Fanchin et al., 2001
) possibly due to the utero-relaxing properties of progesterone, which would make the uterus more `forgiving' to the possible trauma of the clinical feel method. This would explain why the difference in pregnancy rates between the two methods disappears on day 5.
The paper by Prapas et al. would suggest that ultrasound guidance during embryo transfer on day 3 and 4 is desirable. However a paper by Kovacs revealed that clinicians ranked this 11th out of 12 factors of importance for embryo transfer, which could reflect a lack of familiarity with this procedure (Kovacs, 1999). Prapas et al.'s paper furthermore suggests that ultrasound-guidance is less important for day 5 embryo transfers, but it should be noted that the majority of embryo transfers are performed on day 2 or 3 after oocyte retrieval, when the uterus is still very sensitive to stimuli. In view of this, research into pharmacological agents, which have the potential to reduce uterine contractions at the time when the utero-relaxing properties of progesterone are less effective, should be encouraged.
Notes
1 To whom correspondence should be addressed. E-mail: F.P.Biervliet{at}hull.ac.uk
References
Fanchin, R., Righini, C., Olivennes, F., Taylor, S., de Ziegler, D. and Frydman, R. (1998) Uterine contractions at the time of embryo transfer alter pregnancy rates after in-vitro fertilization. Hum. Reprod., 13, 19681974.[Abstract]
Fanchin, R., Ayoubi, J., Righini, C., Olivennes, F., Schönauer, L.M., and Frydman, R. (2001) Uterine contractility decreases at the time of blastocyst transfers. Hum. Reprod., 16, 11151119.
Kovacs, G.T. (1999) What factors are important for successful embryo transfer after in-vitro fertilization? Hum. Reprod., 14, 590592.
Lesny, P., Killick, S.R., Tetlow, R.L., Robinson, J. and Maguiness, S.D. (1998) Embryo transfercan we learn anything new from the observation of junctional zone contractions? Hum. Reprod., 13, 15401546.[Abstract]
Prapas, Y., Prapas, N., Hatziparasidou, A., Vanderzwalmen, P., Nijs, M., Prapa, S. and Vlassis, G. (2001) Ultrasound-guided embryo transfer maximizes the IVF results on day 3 and day 4 embryo transfer but has no impact on day 5. Hum. Reprod., 16, 19041908.