1 14th Department of Obstetrics and Gynaecology, Aristotle University of Thessaloniki, Thessaloniki 2 Iakentro Fertility Center, Thessaloniki, Greece, 3 SIMAF, Van Helmont Hospital, Vilvoorde, Belgium
Dear Sir,
We would like to thank Dr Letterie and Dr Eckert for the interest shown in our manuscript (Prapas et al., 2001) before responding to their comments.
The variable of vaginal microflora and its impact on the likelihood of success after embryo transfer in IVF is indeed still debatable. Different studies have shown a reduction in pregnancy rate occurred when bacteria were recovered from the tip of the embryo transfer catheter (Hillier et al., 1993; Egbase et al., 1996
, 1999
; Fanchin et al., 1998
). It is of interest that the dominant microorganisms differed among the studies. The dominant micro-organisms were group D streptococcus and E. Coli in Kuwait, E. Coli in France and S. Viridans, Enterococcus, species S. epidermidis in the USA. Conversely, it has been shown that hydrogen peroxide-producing Lactobacillus in the vagina appeared to positively impact the live birth rate among women undergoing IVF (Moore et al., 2000
).
Three possible mechanisms have been proposed (Fanchin et al., 1998) to explain the influence of positive culture to the pregnancy rate: (i) The intense concentrations of micro-organisms on the cervix may be associated with subclinical chronic endometritis. In our work this possibility was excluded since every woman had an office hysteroscopy the cycle before IVF. Any case suspected for endometritis was excluded from the IVF programme in order to have endometrial cultures for micro-organisms and the necessary treatment. (ii) The embryo transfer procedure may inoculate cervical micro-organisms into the uterine cavity. This could be the case for embryo transfer performed with compact catheters. Using the Wallace catheters the outer sheath remains in contact with the cervical mucus but the inner catheter going through the sheath is protected and has a lot less chance to be in contact with the micro-organisms. Moreover the tip of the inner catheter never goes beyond the midline of the uterine cavity and therefore the upper half cavity where the drop with the embryos is thrown remains untouchable. (iii) The possible direct contamination of embryos during transcervical embryo transfer may destroy their ability to implant. We believe that evidence of endometrial inflammation following embryo transfer needs to be documented in order to show that bacteria may affect the pregnancy rate in IVF cycles.
It has been suggested (Ralph et al., 1999) that bacterial vaginosis could affect the pregnancy between implantation and 6 weeks gestation but this was not found in another study (Moore et al., 2000
). Moreover, in our protocol every woman has screening tests for vaginal and cervical micro-organisms on day 2021 of the cycle prior to commencing the IVF protocol. In this way cases presenting with bacterial vaginosis were excluded.
In fact vaginal microflora is not a single variable which can be easily accounted for. Numerous factors (such as streptococci, hydrogen peroxide-producing Lactobacillus etc.) influence the status of vaginal microflora and complex statistical models should be used to predict the influence of each factor on the outcome.
Statistical studies giving a `vaginal microflora score' could solve the problem (in that case we would be able to control for equal scores) but further study on this matter is necessary.
In conclusion, the vaginal microflora statusbeing an open issue of studydid not concern our study as a factor of significant influence on the outcome.
Notes
4 To whom correspondence should be addressed E-mail: iakentro{at}otenet.gr
References
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