Department of Obstetrics and Gynaecology, Institute Universitari Dexeus, Pso Bonanova 67, Barcelona, Spain e-mail: vencor@iudexeus.uab.es
Dear Sir,
We thank Dr Mocanu for his interest in our paper. He seems not convinced of the usefulness of ultrasound-guided embryo transfer to increase implantation rates after IVF. Let me respond to the points raised by Dr Mocanu to support his contention.
As physicians, whether serving individual patients or populations, we always have sought to base our decisions and actions on the best possible evidence. Evidence from a properly designed randomized trial is considered as level I (the highest) evidence. Several randomized clinical trials by us and others have shown that ultrasound-guided embryo transfer improves pregnancy rates after IVF (Coroleu et al., 2000; Wood et al., 2000
; Tang et al., 2001
; Matorras et al., 2002
).
The report by Sundstrom et al. (1984) quoted by Dr Mocanu to support the supposed benefit of the full bladder during embryo transfer is a small and uncontrolled study of 14 embryo transfers with a full bladder compared retrospectively with 14 embryo transfers with empty bladder. Remarkably, in that short communication it is stressed..."the technique is described for easy passage of the catheter into the uterine cavity in women who have anteverted uterus". Therefore, the technique would not apply in women having a non-anteverted uterus. On the other hand, in a randomized study in 66 women with full bladders, compared with 76 women with empty bladders, Mitchell et al. (1989
) found no significant differences in difficulties encountered at embryo transfer or in pregnancy rate.
Ultrasound guidance is especially helpful with the insertion of soft catheters increasing the frequency of easy transfers and pregnancy rates (Matorras et al., 2002), and the use of a soft catheter is considered as an important factor for successful embryo transfer (Kovacs, 1999
; Salha et al., 2001
).
As an atraumatic embryo transfer is essential for successful implantation (Kovacs, 1999; Salha et al., 2001
), in our studies (Coroleu et al., 2000
, 2002) the soft inner catheter was introduced into the cervix and passed through the internal cervical os without using the outer sheath whenever possible. The level of insertion of transfer catheter is obviously best determined by ultrasonography. In fact, the trial transfer was proposed in the literature owing to the great variability in cervical and uterine anatomy.
As stressed above, treatments in reproductive medicine should be tested in rigorous randomized controlled trials. This means that groups compared should be similar with respect to variables that can influence the outcome. It has been shown that pregnancy rates after embryo transfer depend on the provider at embryo transfer (Karande et al., 1999; Hearns-Stokes et al., 2000
). Therefore, a feature of our studies (Coroleu et al., 2000
, 2002) is that all embryo transfers were carried out by the same provider.
References
Coroleu, B., Carreras, O., Veiga, A., Martell, A., Martinez, F., Belil, I., Hereter, L. and Barri, P.N. (2000) Embryo transfer under ultrasound guidance improves pregnancy rates after in-vitro fertilization. Hum. Reprod., 15, 616620.
Coroleu, B., Barri, P.N., Carreras, O., Martinez, F., Parriego, M., Hereter, L., Parera, N., Veiga, A. and Balasch, J. (2002) The influence of the depth of embryo replacement into the uterine cavity on implantation rates after IVF: a controlled, ultrasound-guided study. Hum. Reprod., 17, 341346.
Hearns-Stokes, R.M., Miller, B.T., Scott, L., Creuss, D., Chakraborty, P.K. and Segars, J.H. (2000) Pregnancy rates after embryo transfer depend on the provider at embryo transfer. Fertil. Steril., 74, 8086.[CrossRef][ISI][Medline]
Karande, V.C., Morris, R., Chapman, C., Rinehart, J. and Gleicher, N. (1999) Impact of the physician factor on pregnancy rates in a large assisted reproductive technology program: do too many cooks spoil the broth? Fertil. Steril., 71, 10011009.[CrossRef][ISI][Medline]
Kovacs, G.T. (1999) What factors are important for successful embryo transfer after in-vitro fertilization? Hum. Reprod., 14, 590592.
Matorras, R., Urquijo, E., Mendoza, R., Corcóstegui, B., Expósito, A. and Rodriguez-Escudero, F.J. (2002) Ultrasound-guided embryo transfer improves pregnancy rates and increases the frequency of easy transfers. Hum. Reprod., 17, 17621766.
Mitchell, J.D., Wardle, P.G., Foster, P.A. and Hull, M.G. (1989) Effect of bladder filling on embryo transfer. J. In Vitro Fert. Emb. Trans., 6, 263265.[ISI][Medline]
Salha, O., Lamb, V.K. and Balen, A. (2001) A postal survey of embryo transfer practice in the UK. Hum. Reprod., 16, 686690.
Sundstrom, P., Wransby, H., Person, P.H. and Liedhom, P. (1984) Filled bladder simplifies human embryo transfer. Br. J. Gynaecol., 91, 506507.[ISI]
Tang, O.S., Ng, E.H.Y., So, W.W.K. and Ho, P.C. (2001) Ultrasound-guided embryo transfer: a prospective randomized clinical trial. Hum. Reprod., 16, 23102315.
Wood, E.G., Batzer, F.R., Go, K.J., Gutmann, J.N. and Corson, S.L. (2000) Ultrasound-guided soft catheter embryo transfers will improve pregnancy rates in in-vitro fertilization. Hum. Reprod., 15, 107112.