Hum. Reprod. Advance Access originally published online on October 11, 2007
Human Reproduction 2008 23(2):457-458; doi:10.1093/humrep/dem320
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Letters to the Editor |
Ultrasound guided embryo transfer does not offer any benefit in clinical outcome: a randomized controlled study
Assisted Reproduction Unit, American Hospital of Istanbul, Guzelbahce Sokak No. 20, Nisantasi, Istanbul 34365, Turkey
1 Correspondence address. Tel: +90-532-744-74-16; Fax: +90-224-232-24-75; E-mail: barisata{at}hotmail.com
We read the article by Kosmas et al. (2007)
with great interest. Several trials and one meta-analysis reported higher pregnancy rates with ultrasound guided embryo transfer (USET) compared with non-ultrasound guided embryo transfers (NUSET) (Buckett, 2003). These authors conducted a large single center randomized controlled trial and concluded that transabdominal ultrasound guidance during embryo transfer did not improve clinical pregnancy and implantation rates provided that the transfer was performed by an experienced operator. We concur that large randomized trials can yield contradictory results to previously published meta-analyses that include smaller studies (LeLorier et al., 1997). However, we have several concerns regarding the design of the present study and reporting and conclusions drawn from the results.
First, trials included in the meta-analysis by Buckett have demonstrated consistently higher absolute pregnancy rates after USET performed with a full or at least a moderately full bladder, compared with NUSET. Trials, in which these differences did not reach statistical significance, did not have adequate statistical power to demonstrate significance between the actually observed values (Kan et al., 1999; Garcia-Velasco et al., 2002), and this is why meta-analyses are done. A full bladder was required for USET in all included studies; therefore, the conclusion of the meta-analysis may be better stated as ‘ultrasound guided embryo transfer with a full bladder significantly increases the chance of clinical pregnancy and the embryo implantation rate’. We believe that USET with and without a full bladder are different entities. In Kosmas et al.'s trial a full bladder was not required for USET and the authors justified this by referring to an inadequately powered ‘pilot’ study that compared outcome of embryo transfers performed under US guidance with or without a full bladder and embryo transfers performed with the ‘clinical touch’ method (Lorusso et al., 2005). We do not think that the results of a single pilot study are sufficient to justify a USET protocol with an empty bladder.
A full bladder during transabdominal ultrasound guidance not only facilitates visualization of the cervical canal and the endometrial strip, but also renders the negotiation of the cervico-uterine junction easier by decreasing anteflexion of the uterus in women with an anteverted uterus. Sallam et al. (2002) demonstrated that pregnancy rate after embryo transfer was inversely associated with the degree of uterine anteflexion.
Transabdominal ultrasound even performed with a full bladder may not be of sufficient guidance in 10% of patients undergoing embryo transfer (Garcia-Velasco et al., 2002). This figure can be expected to be higher when the bladder is empty, and in Kosmas et al.'s trial, a substantial number of subjects may have emptied their bladder before ET as the decision was left to the patient. The results of the present study may have been better evaluated had the authors reported (i) the proportion of women who had an empty or full bladder at the time of embryo transfer in both groups, (ii) the proportion of the procedures where the ultrasonographic view was satisfactory, i.e. they were able to follow the catheter tip throughout the procedure and (iii) whether having a full bladder or not affected the visualization of the embryo transfer procedure. If a substantial number of women undergoing USET had not had a full bladder during embryo transfer procedures, then this trial should be regarded as evaluating a different situation from previous trials evaluating USET.
Another point of concern is the outer cervical os–catheter tip distance being significantly different between the study groups in Kosmas et al.'s study. Although the authors have reported the mean distances and standard deviations, they have not reported the ranges for these measurements. In some women, the depth of the endometrial cavity may be at the lower or upper extreme of the ranges reported as normal. We have been measuring lengths of the cervical canal and the endometrial cavity during embryo transfer in the context of an ongoing trial, and according to our preliminary data in over 200 women, the external cervical os–uterine fundus distance (CFD) ranges between 48 and 110 mm; 25% of women having a CFD of <6 cm and 10% having a CFD of >8 cm (unpublished data). Therefore, if embryos are routinely transferred at the 6th cm from the external cervical os without ultrasound guidance, the catheter will touch the fundus in the first group, and embryos will be dislodged at >2 cm distance to the fundus in the latter group. Regarding these facts one can conclude that even if USET does not benefit the majority of women, it may be of great benefit in women who do not comply with the population average. Unfortunately a trial with adequate power to demonstrate this benefit would require a substantially large number of subjects.
In conclusion, embryo transfer is a crucial step of assisted reproduction treatment, USET is a noninvasive procedure, and most IVF units, if not all, already have ultrasound equipments that may be utilized for embryo transfer. Therefore, we believe avoidance of using ultrasound to guide embryo transfer is not to the best interest of patients.
References
Buckett WM. A meta-analysis of ultrasound-guided versus clinical touch embryo transfer. Fertil Steril (2003) 80:1037–1041.[CrossRef][Web of Science][Medline]
Garcia-Velasco JA, Isaza V, Martinez-Salazar J, Landazabal A, Requena A, Remohi J, Simon C. Transabdominal ultrasound-guided embryo transfer does not increase pregnancy rates in oocyte recipients. Fertil Steril (2002) 78:534–539.[CrossRef][Web of Science][Medline]
Kan AK, Abdalla HI, Gafar AH, Nappi L, Ogunyemi BO, Thomas A, Ola-ojo OO. Embryo transfer: ultrasound-guided versus clinical touch. Hum Reprod (1999) 14:1259–1261.
Kosmas IP, Janssens R, De Munck L, Al Turki H, Van der Elst J, Tournaye H, Devroey P. Ultrasound-guided embryo transfer does not offer any benefit in clinical outcome: a randomized controlled trial. Hum Reprod (2007) 22:1327–1334.
LeLorier J, Gregoire G, Benhaddad A, Lapierre J, Derderian F. Discrepancies between meta-analyses and subsequent large randomized, controlled trials. N Engl J Med (1997) 337:536–542.
Lorusso F, Depalo R, Bettocchi S, Vacca M, Vimercati A, Selvaggi L. Outcome of in vitro fertilization after transabdominal ultrasound-assisted embryo transfer with a full or empty bladder. Fertil Steril (2005) 84:1046–1048.[CrossRef][Web of Science][Medline]
Sallam HN, Agameya AF, Rahman AF, Ezzeldin F, Sallam AN. Ultrasound measurement of the uterocervical angle before embryo transfer: a prospective controlled study. Hum Reprod. 17:1767–1772.
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