Six mature oocytes may be optimal for live birth through ART
Last Updated: 2011-07-19 18:35:05 -0400 (Reuters Health)
By Rob Goodier
NEW YORK (Reuters Health) - Contrary to conventional wisdom, harvesting more oocytes for assisted reproduction isn't necessarily better, a new study suggests.
Harvesting six or more metaphase II oocytes gives better odds for a live birth than harvesting fewer, but there's no advantage to harvesting 10 or more, according to research published online June 28 in Fertility and Sterility.
Doctors should "consider less aggressive protocols for ovarian stimulation for ART," said senior investigator Dr. Alex Polotsky from the University of Colorado, Denver in email to Reuters Health.
"The as-many-as-possible-oocyte-yield approach for ART does not provide an improvement in take-home baby rates, yet it is associated with the increased risk of ovarian hyperstimulation and a higher financial burden," Dr. Polotsky said.
He and his colleagues reviewed data on 737 infertile women treated between 2002 and 2008. Thirty percent of ART cycles resulted in live births.
As expected, cycles that resulted in live birth started with more mature oocytes: 11.0, on average, vs 9.7 obtained for unsuccessful cycles (P<0.01). Successful cycles also had higher average maturation rates, at 82.6% compared to 77.9% (P<0.01).
After adjusting for age and maximum baseline levels of follicle-stimulation hormone (FSH), multivariate logistic regression models showed that cycles with six to nine mature oocytes resulted in the most live births.
The researchers also compared cycles with differing numbers of oocytes to a reference group with an average of 10 to 14 oocytes. Cycles with five or fewer oocytes led to significantly fewer live births (odds ratio: 0.61, P=0.048). There was no statistical difference, however, between the reference group and cycles that began with six or fewer oocytes.
Therefore, the researchers conclude, for the best odds of a live birth the minimum number of oocytes needed is six and the optimum range is six to nine.
Figuring out the mechanisms that underlies at work that would explain these findings will require further research, Dr. Polotsky says. "It may have to do with the impact of high blood hormone levels (estradiol and progesterone) on egg quality and endometrium."
This study, he says, should encourage doctors to "reconsider a long-held dogma that more is always better."
SOURCE:http://bit.ly/pFHyD0
Fertil Steril 2011.
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