{"paper_id":"238fcdef-bc35-40d6-b64e-ea65b0f8d21d","body_text":"Implantation is a complex, important process ( 1  ).\nEmbryo quality and uterine receptivity are important\nfactors that influence the outcome of assisted reproductive\ntechnology (ART). Various substances such\nas cyclic adenosine monophosphate (cAMP), relaxin,\ngonadotropin, prostaglandin E2 (PGE2), and glycoprotein\nhormones that are secreted from the embryo\nor endometrium affect implantation ( 2  - 7  ). Secretion\nof human chorionic gonadotropin (HCG) is one of\nthe initial embryonic signals. It is probably a major\nregulator of the embryo-endometrial relationship.\nExpression of the HCG/luteinizing hormone (HCG/\nLH) receptor is observed in the endometrium during\nthe secretory phase of menstrual cycles ( 7  ). HCG is\nusually defined as a key factor that can induce and\ndevelop  in vitro  decasualization of the endometrium\n( 6  ,  8  ). HCG may have systemic and local effects on\nthe embryo-endometrial microenvironment ( 9  ).\nPregnancy rates following cryopreserved embryo\ntransfer cycles are usually lower than fresh\nembryo transfer cycles. However, transfer of excess\nembryos in frozen cycles increases the cumulative\npregnancy rates and decreases the costs. So\nan attempt to evaluate the factors that influence the\nsuccess rate of cryopreserved cycles is important\n( 9  ,  10  ). The aim of this study is to assess the advantage\nof HCG supplementation during the secretory phase of hormonally-prepared cycles for the\ntransfer of cryopreserved-thawed embryos.\n\nThis randomized clinical trial was conducted at\nthe Yazd Research and Clinical Center for Infertility,\nShahid Sadoughi University of Medical Sciences\nbetween January 2009 and June 2011. The study was\napproved by the Ethics Committee of the university.\nWritten informed consent was obtained from all\ncouples. Women who had undergone  in vitro  fertilization\n(IVF) or intracytoplasmic sperm injection\n(ICSI) with cryopreservation of excess embryos and\nfresh cycles with implantation failure entered the\nstudy. Women older than 38 years, those with a body\nmass index (BMI) >30 kg/m 2 , history of endocrine\ndisorders, and severe endometriosis were excluded\nfrom the study. The patients were allocated into two\ngroups: group 1 (HCG) and group 2 (control) as performed\nby computerized randomization.\nMorphological assessment of all embryos was\nperformed on the second day after oocyte retrieval.\nWe transferred two or three embryos. Any excess\nembryos that had less than 30% fragmentation were\nfrozen by the vitrification method. After a two-step\nloading with equilibrant and vitrification solutions,\nembryos were loaded by a thin glass capillary on to\nthe cryoton. After loading, nearly the entire solution\nwas eliminated and only a fine layer covering the\nembryos remained. The embryos were flooded in to\nliquid nitrogen, a film part of cryoton was covered\nby a plastic cap, and we stored the sample in liquid\nnitrogen. Thawing was performed at least two\nmonths after cryopreservation, when straws were\nexposed to air and then submerged in water. The\ncryoprotectant was eliminated using embryo-thawing\nmedia (Vitrolife). After thawing, the embryos\nwere transferred to a culture media and evaluated\n24 hours later. We selected those embryos with less\nthan 50% fragmentation for transfer.\nThe endometrial preparation process was similar\nin both groups. All women received oral estradiol\nvalerate (2 mg, Aburaihan Co., Tehran, Iran) 6 mg\nper day from the second day of the menstrual cycle.\nEndometrial thickness was measured by vaginal ultrasonography.\nFrom the 13 th  day of the cycle when\nendometrial thickness reached 8 mm, intramuscular\n(IM) injections of progesterone in oil (100 mg;\nAburaihan Co., Tehran, Iran) were administered to\nall subjects. Embryo transfer was performed three\ndays after the beginning of progesterone administration.\nEstradiol and progesterone were continued\nuntil the tenth week of gestational age.\nIn the HCG group, 5000 IU HCG (Pregnyl®, Organon,\nOss, Netherlands) was injected on the first\nday of progesterone administration and on the day\nof embryo transfer. Embryo thawing was performed\ntwo days after the first progesterone injection. Embryos\nwere transferred one day after thawing by a\nLabotect catheter (Labotect, Gotting, Germany).\nChemical pregnancy was defined by serum β hCG\n>50 IU/L 12 days after embryo transfer and clinical\npregnancy was defined by observation of fetal heart\nactivity two weeks after positive β hCG. We defined\nmiscarriage as the loss of pregnancy before the 20 th \nweek of gestation and ongoing pregnancy as continuation\nof pregnancy after the 12 th  week of gestation.\nImplantation rate was defined as the numbers\nof gestational sacs per 100 embryos transferred.\nStatistical analysis was carried out using the statistical\npackage for the social sciences (SPSS version\n15.0 for Windows, Chicago, IL). Both t test\nand chi-square test were used to detect significant\ndifferences between two groups. The level of significance\nwas set at p value<0.05.\nIn this study, a total of 130 couples participated:\n65 in group 1 (HCG group) and 65 in group 2 (control\ngroup). The demographic and basic characteristics\nof patients are shown in table 1.\nThere were no statistically significant differences\nbetween groups regarding age (p=0.549), duration\nof infertility (p=0.368), basal follicle stimulating\nhormone (p=0.135), BMI (p=0.661), and etiology\nof infertility (p=0.201). The cycle characteristics\nand outcome of vitrification are shown in table 2.\nThere were no statistically significant differences\nbetween groups regarding the numbers of thawed embryos,\nnumbers of transferred embryos, survival rates\nof thawing embryos and duration of freezing. Table\n3 shows the outcome of ART cycles. Implantation,\nchemical pregnancy, clinical pregnancy, ongoing pregnancy, and abortion rates were similar in both groups.\nBasic patient characteristics in the two groups\nCycle characteristics and outcome of vitrification\nART outcome in both groups\nWhile treatment protocols, early embryo development,\nand laboratory techniques have considerably improved\nover the last decades in ART cycles, little has been identified\nabout the events that occur after the transfer of embryos\nin to the uterine cavity. About 75% of embryos do\nnot implant after transfer. Thus, to improve implantation\nrates we need additional understanding of the molecular\nmechanisms governing the endometrial preparation for\nembryo implantation ( 11  - 13  ).\nAccording to our data, for better embryo implantation\nit is necessary to have a good embryo with appropriate\nmorphology and developmental potential\nas well as a high concentration of HCG. In this study\nwe have hypothesized that HCG supplementation in\nthe secretory phase of the endometrium during the\nfrozen embryo cycle may increase the implantation\nand eventually the pregnancy rate. However our findings\nhave contradicted with this hypothesis.\nOur study showed that HCG supplementation for\nendometrial preparation in cryopreserved cycles had\nno more benefit than estradiol and progesterone.\nOur finding was consistent with the Ben-Meir et al.\nstudy where the researchers observed that recombinant\nHCG supplementation during the secretory\nphase of the frozen-thawed embryo transfer cycles\nshowed no advantage in terms of pregnancy and implantation\nrates ( 9  ). Similar to our study, they did\nnot use a GnRH agonist for down-regulation, and\nthus endogenous basal LH secretion was not completely\nsuppressed. Tesarik et al. ( 14  ) demonstrated\nthat HCG supplementation during the luteal phase\nof the oocyte donation cycle improved pregnancy\nrates only in cycles with low endogenous LH.\nMansour et al. ( 15  ) have shown that intrauterine\ninjection of 500 IU HCG prior to embryo transfer\nsignificantly increased pregnancy rate after ART.\nThey concluded that the HCG level positively correlated\nwith the level of trophoblastic tolerance.\nHCG plays a central role in controlling implantation\nand early embryonic development ( 16  ). This hormone\nis produced very early by the developing embryo and\nis secreted in relatively high concentrations. HCG may\neffectively regulate endometrial preparation via the\nfollowing processes ( 17  ): i. local down-regulation of\ninsulin growth factor binding protein 1 (IGF BP-1)\nby HCG leads to the prolongation of the window of\nendometrium; ii. HCG augments the endometrial receptivity\nby increasing angiogenesis through increased\nlocal vasoendothelial growth factor (VEGF) ( 18  ,  19  );\niii.HCG interacts with the production of galactosemic\nfibroblast (M-GSF) and leukemia inhibiting factor\n(LIF) that are important for implantation ( 20  ); iv. HCG\nsignificantly inhibits the production of metalloproteinase ( 21  ); and v. HCG has been demonstrated to have\nan impact on the trophoblasts, resulting in improved\ndifferentiation and invasion potential ( 7  ,  22  ).\nFatemi et al. have concluded that the spontaneous\nnatural cycle is superior to the HCG induced natural\ncycle. They showed a negative effect of HCG\nadministration on pregnancy. These researchers hypothesized\nthat the significantly lower pregnancy\nrate in the HCG group was related to desynchronization\nbetween a receptive endometrium and embryo,\nwhich resulted from the endometrial effects of HCG.\nAdministration of HCG has been shown to induce\na series of events in the endometrium which begins\nseveral days later. These events may have a negative\nimpact on implantation ( 23  ). Additional studies with\nlarger sample sizes are required for better evaluation.\n\nWhile HCG has some advantages in the ART cycle,\nour study did not show any advantage of HCG supplementation\nin the secretory phase of frozen cycles.","source_license":"CC-BY-4.0","license_restricted":false}