Outcome after fresh versus frozen embryo transfer inICSI Technique

Abstract

Invitrofertilization(IVF) has beenperformedformore than 30years,anditisestimatedthatindevelopedcountries, more than1%ofall birthsaregeneratedfrom assisted reproductivetherapies (ART).

Implantation is one of most important steps for achieving ART success,anditseffectivenessreliesupon embryoquality, a reciprocalembryo-endometriuminteraction (which isdependentonfactors suchasembryoand endometrial quality), andendometrial receptivity.

Theimplantationwindowisa self-limitedperiodmarked by structuralandfunctionalmaturationofthe endometrium, which is necessary for embryo attachment. During thisperiod, theendometrium undergoestransformationsmediated by alargenumberofgenesandgeneproducts,whichare differentiallyexpressedduringthe receptive phase ofthe menstrual cycle.

Thereisevidence thatthe supraphysiologiclevelsof estradiol and progesterone during COScouldleadto morphologic and biochemical modifications, and

consequently impairendometrialreceptivity. Suchchanges may leadtoembryo-endometriumasynchrony,thereby reducing theimplantation ratesduring IVF/ICSItreatments. Higherlevelsofestradiolmay leadtoalterationsin endometrial maturationandimplantation.

These alterationsmay resultinembryo-endometrium asynchrony,and theymaydecreasetheimplantation rates duringART treatmentsincase offreshembryotransferis performed.

Endometrial developmentand primingarecontrolled more precisely during frozen-thawedcycleswhencompared toCOSwithgonadotrophins, andthiscouldbe relatedto better endometrial receptivity, favoring those patients adoptingthefreezingpolicy.

Cryopreservation of humanembryoshasbeena routine componentofclinicalin-vitrofertilization(IVF) programmes forwellovera decade.Intreatmentcycleswhereovarian stimulationinconjunctionwithIVFresultinalargenumber offertilizedoocytes, itoffersthe opportunity toreduce the numberof embryostransferred per procedure.and thereby restricttheriskofmultiplepregnancy,whileoptimizingthe

clinicaluse ofavailable material. Ifthere isa surplus of embryos leftafter embryo transfer ,then those could be frozen,thisallowedthe womenachance touse the frozen embryosfora second pregnancy oralsoa secondattemptat the first pregnancy ifshe was unsuccessfulwiththe fresh embryo transfer.