Impact Of The Number Of Retrieved Oocytes On Pregnancy Outcome And Cumulative Live Birth Rate Of Fet In Freeze-all Cycles

Objective:To investigate the relationship among the number of retrieved oocytes,pregnancy outcome and cumulative live birth rate of FET in freeze-all cycles avoiding OHSS.Methods:We retrospectively examined the freeze-all cycles avoiding OHSS behind controlled ovarian hyperstimulation of 191 women undergoing their first IVF/ICSI therapy using GnRH agonist long protocol at Guangxi Center for Reproductive Medicine of The First Affiliated Hospital of Guangxi Medical University from July 1^st in 2014 to July 31^st in 2016.We divided them into three groups based on the number of retrieved oocytes,namely,A group（15～20）,B group（21～25）,C group（>25）.We conducted this study to evaluate and compare their baseline information,laboratory and pregnancy outcome in these three groups,including age,basic follicle stimulating hormone（FSH）levels,female BMI,the choice of fertilization mode,the total dosages of gonadotropin,fertilization rate,high-grade embryo rate,transferable embryos formation rate,clinical pregnancy rate,cumulative live birth rate and so on.Multivariate logistic regression was used to assess the association between oocyte number and cumulative live birth rate of each COH cycle after adjusting for confounding factors.Result:（1）There were no significant differences in ages,basic follicle stimulating hormone（FSH）levels,female BMI,the choice of fertilization mode,the total dosages of gonadotropin and other baseline parameters among A,B and C group.A group has not OHSS patient.C group has higher OHSS incidence rate than B group,without significant differences.（2）With the increase of the number of oocytes retrieved,the IVF fertility rate shows gradually upward trend,although there are not significant differences.The IVF 2PN fertility rate of B and C groups are significantly higher than A group,while C group’s is lower than B group,without significant differences.The high-grade embryo rate of B group is significantly higher than C group.（3）With the increase of the number of oocytes retrieved,blastocyst transfer presents gradually upward trend,without significant differences.There are not significant differences among A,B and C groups in implantation rate,clinical pregnancy rate,the first FET live birth rate（56.8%）,the second FET live birth rate（40.0%）,the third FET live birth rate（57.1%）.But B group is higher than A and C groups.B group demonstrated the highest cumulative live birth rate,with significant differences.（4）Logistic regression analysis of cumulative live birth rate using A group as the reference category showed that B group OR was 2.407（0.971⁵.970）,C group OR was 0.977（0.410².331）.There are significant differences with adjustment for confounding factors affecting pregnancy rates.Conclusion:（1）The number of retrieved oocytes is a independent influencing factor for predicting cumulative live birth rate under the freeze-all stratege avoiding OHSS.（2）The cumulative live birth rate is first increased and then decreased along with the number of retrieved oocytes.21～25 group has the highest cumulative live birth rate with adjustment for confounding factors affecting pregnancy rates and lower moderate-severe OHSS morbidity.（3）Freeze-all stratege is the better choice for high OHSS risk patients under the COH.