| Rogue bug may cause IVF failure|
|Fluid near the ovaries may be harbouring to bacteria that reduces a woman's chances of becoming pregnant through assisted reproduction, says an Australian researcher.|
Microbiologist Dr Christine Knox, of the Queensland University of Technology, says the finding overturns the traditional view that fluid surrounding the ovum, known as follicular fluid, is sterile.
She believes her research may help increase the success rates of assisted reproductive technologies (ART), and believes the bacteria could be responsible for infertility cases that have no apparent cause.
Knox, and colleagues at the Wesley Monash IVF clinic, tested the fluid surrounding individual eggs taken from the ovaries of 31 women undergoing ART.
In 21 of the samples they found bacteria in the follicular fluid, a result Knox says was startling because "traditionally it was assumed the fluid surrounding the ovum was sterile".
Knox says the finding has since been replicated in a larger study funded by The Wesley Research Institute.
In that study Knox and doctoral student Elise Pelzer analysed the follicular fluid of 148 women and found bacteria in the fluid of all but one woman.
She says further tests showed the bacteria had, in some cases, been transferred from the lower genital tract to the follicular fluid during the medical procedure used to collect eggs known as TVOR, or transvaginal oocyte retrieval.
But, she says in 52 of the women the follicular fluid contained bacteria that was not found in the lower tract.
Knox says it is these unique, colonising bacteria that appear to play a role in reducing pregnancy outcomes.
Of those women with follicular fluid colonised by this bacteria, only 25% achieved a successful pregnancy, she says.
This compared with a 50% success rate for those who had bacteria introduced into the fluid during TVOR.
"We also found that eggs from women with colonised follicular fluid had a lower rate of fertilisation to start with, which, of course, meant they produced fewer embryos for transfer to the womb," she says.
Knox says they are still working on the results to see if they can pinpoint the strain of bacteria that lead to the reduced pregnancy outcomes.
If they can identify which ones are responsible, it may be possible to screen women for their presence, she says.
Knox says the finding also has implications for 20% of couples who have no known cause for their infertility.
"It might be a matter of also screening these couples to see if these bacteria are present," she says
According to Knox, the risk factors for having infected follicular fluid and poor pregnancy outcomes appears to be: length of infertility before ART; previous ART with TVOR; and a past history of damage to the Fallopian tubes.
Contamination not new
Professor Michael Chapman, head of the School of Women's Health at the University of New South Wales, says the finding is not new.
"[Professor] Peter Braude from St Thomas's Hospital in London showed significant contamination in follicular fluid as far back as 1994 in the early days of TVOR," he says.
"It made no difference to pregnancy rates."
Chapman, says the risk factors Knox highlights are "well-recognised negative factors" in pregnancy outcome.
"Thus to suggest bacterial contamination is significant requires these factors to be corrected for," he says.
"The reason for the high levels of contamination is the fact that the vagina is colonised, like the mouth, with a host of commensal bacteria. These are impossible to eradicate even though we wash out the vagina with antiseptic pre-TVOR."
Knox says her study does lend support to previous work that shows contamination at the time of egg collection does occur.
But, she says more than a third of women in the larger study had bacteria in the follicular fluid that was not in the vaginal tract, and that it highlights a new, previously unknown source.
"It is these women who had the adverse [pregnancy] outcomes," she says.