en <p>GnRH analogue, HMG and HCG administration are common protocol for ovulation induction in assisted reproductive technology (ART). Since implantation rate in stimulated ART cycles is lower than unstimulated cycles and as endometrium plays an important role in embryo receptivity, effect of this protocol on the ultrastructure of human endometrial glandular epithelium was studied at LH+4 (embryo transfer time). In this research endometrial biopsies were obtained from fertile women as well as infertile women who had undergone this protocol at LH+4. Quantitative and qualitative studies on endometrial glandular epithelium was performed by transmission electron microscopy (TEM) and morphometry and the results were statistically compared between the two groups. Qualitative results revealed presence of nuclear channel system (NCS), sub vacuole of glycogen and giant mitochondria (GM) in both groups. Similarly, in quantitative analysis, the volume fractions (Vv) of glycogen, mitochondria and rough endoplasmic reticulum to cell and also the Vv of euchromatin to nucleus were statistically not different (P&gt; 0.05). These results suggest that ovulation induction by GnRH analogue, HMG and HCG are not associated with advanced endometrial development and consequently, embryo transfer at this stage (before advanced endometrial development which occurs normally at LH+7 to LH+10) may cause a lower rate of implantation.</p> تکامل اندومتر، آگونیست GnRH، گنادوتروپین یائسگی انسان، گنادوتروپین جفتی انسان، مورفومتری Endometrial development, GnRH agonist, Human menopausal genadotropin, HCG, Morphometry 4 13 https://www.jri.ir/article/70 https://www.jri.ir/documents/fullpaper/fa/70.pdf FereshtehMehraeinHistology Department, Faculty of Medicine, Tabriz Medical Sciences University, Tabriz, Iranفرشتهمهرآئين162MaerefatGhaffariMajidi Infertility Center, Faculty of Medicine, Tabriz Medical Sciences University, Tehran, Iranمعرفتغفاري نوینmghaffarin@yahoo.com71JafarSoleimaniradAnatomy Department, Faculty of Medicine, Tabriz Medical Sciences University, Tabriz, Iranجعفرسليماني راد163Mohammad HasanHeydariAnatomy Department, Faculty of Medicine, Shahid Beheshti Medical Sciences University, Tehran, Iranمحمد حسنحيدري167Shir AhmadSaraniAnatomy Department, Faculty of Medicine, Zahedan Medical Sciences University, Zahedan, Iranشير احمدساراني165LaeyaFarzadiMajidi Infertility Center, Faculty of Medicine, Tabriz Medical Sciences University, Tabriz, Iranلعيافرزدي117AliehGhasemzadehMajidi Infertility Center, Faculty of Medicine, Tabriz Medical Sciences University, Tabriz, Iranعاليهقاسم زاده166MohammadNouriMajidi Infertility Center, Faculty of Medicine, Tabriz Medical Sciences University, Tabriz, Iranمحمد نوري 143