Ovarian stimulation using human chorionic gonadotrophin impairs blastocyst implantation and decidualization by altering ovarian hormone levels and downstream signaling in mice

Repeated ovarian hyperstimulation promotes depression-like behavior in female mice

Controlled ovarian hyperstimulation (COH) is a common step for treating infertile couples undergoing assisted reproductive technologies and in female fertility preservation cycles. In some cases, undergoing multiple COHs is required for couples to conceive. Behavioral changes such as anxiety and depression can be caused by ovulation-inducing drugs. Sex steroids play a role in locomotor activity, behavioral changes, and nociception, specifically during fluctuations and sudden drops in estrogen levels. This study evaluated the effect of repeated ovarian hyperstimulation (ROH) on weight, locomotor activity, anxiety-like and depression-like behavior, and nociception in female mice. The animals were divided into two groups: control (placebo; Control) and treated (ROH; Treatment). Ovulation was induced once weekly for 10 consecutive weeks. Locomotor activity (open field test), anxiety-like behavior (elevated plus maze, hole board, and marble burying tests), depression-like behavior (splash and forced swim tests), and nociception (hot plate and Von Frey tests) were evaluated before and after ROH. Statistical analysis was conducted using two-way analysis of variance to evaluate the effects of ROH, age of mice, and their interaction. The results suggested that ROH contributed to weight gain, increased locomotor activity, and induced depression-like behavior in female mice. Furthermore, the age of the mouse contributed to weight gain, increased locomotor activity, and induced anxiety-like and depression-like behavior in female mice. ROH could change the behavior of female mice, particularly inducing depression-like behavior. Further studies are required to evaluate various COH protocols, specifically with drugs that prevent fluctuations and drastic drops in estrogen levels, such as aromatase inhibitors.

Gynotoxic Effects of Chemotherapy and Potential Protective Mechanisms

Chemotherapy is one of the leading cancer treatments. Unfortunately, its use can contribute to several side effects, including gynotoxic effects in women. Ovarian reserve suppression and estrogen deficiency result in reduced quality of life for cancer patients and are frequently the cause of infertility and early menopause. Classic alkylating cytostatics are among the most toxic chemotherapeutics in this regard. They cause DNA damage in ovarian follicles and the cells they contain, and they can also induce oxidative stress or affect numerous signaling pathways. In vitro tests, animal models, and a few studies among women have investigated the effects of various agents on the protection of the ovarian reserve during classic chemotherapy. In this review article, we focused on the possible beneficial effects of selected hormones (anti-Müllerian hormone, ghrelin, luteinizing hormone, melatonin), agents affecting the activity of apoptotic pathways and modulating gene expression (C1P, S1P, microRNA), and several natural (quercetin, rapamycin, resveratrol) and synthetic compounds (bortezomib, dexrazoxane, goserelin, gonadoliberin analogs, imatinib, metformin, tamoxifen) in preventing gynotoxic effects induced by commonly used cytostatics. The presented line of research appears to provide a promising strategy for protecting and/or improving the ovarian reserve in the studied group of cancer patients. However, well-designed clinical trials are needed to unequivocally assess the effects of these agents on improving hormonal function and fertility in women treated with ovotoxic anticancer drugs.

Superovulation with an anti-inhibin monoclonal antibody improves the reproductive performance of rat strains by increasing the pregnancy rate and the litter size

Rats are multiparous rodents that have been used extensively in research; however, the low reproductive performance of some rat strains hampers the broader use of rats as a biomedical model. In this study, the possibility of increasing the litter size after natural mating in rats through superovulation using an anti-inhibin monoclonal antibody (AIMA) was examined. In outbred Wistar rats, AIMA increased the number of ovulated oocytes by 1.3-fold. AIMA did not affect fertilization and subsequent embryonic development, resulting in a 1.4-fold increase in litter size and a high pregnancy rate (86%). In contrast, conventional superovulation by eCG/hCG administration decreased the pregnancy rate to 6-40% and did not increase the litter size. In inbred Brown Norway rats, AIMA increased the litter size by 1.2-fold, and the pregnancy rate increased more than twice (86% versus 38% in controls). AIMA also increased the litter size by 1.5-fold in inbred Tokai High Avoiders and Fischer 344 rats. AIMA increased the efficiency of offspring production by 1.5-, 2.7-, 1.4-, and 1.4-fold, respectively, in the four rat strains. Thus, AIMA may consistently improve the reproductive performance through natural mating in rats, which could promote the use of AIMA in biomedical research.

Cuyun Recipe ameliorates pregnancy loss by regulating macrophage polarization and hypercoagulable state during the peri-implantation period in an ovarian hyperstimulation mouse model

BACKGROUND

The Chinese herbal prescription Cuyun Recipe (CYR) has been widely used to treat clinical infertility and has shown good efficacy. Animal experiments have shown that CYR can promote implantation in mice, however, the exact mechanism underlying the implantation has not been elucidated.

PURPOSE

To investigate the effect and mechanism of CYR on regulating macrophage polarization and hypercoagulability during the peri-implantation period in mice with ovarian hyperstimulation.

METHODS

An ovarian hyperstimulation mouse model was developed, followed by treatment with CYR. Mice were sacrificed on day (D)4.5, D6, or D8 of gestation. The number of implantation sites, the pathological changes of the uterus and ovaries were assessed. The polarization of monocytes/macrophages in the spleen and endometrium, the expression and localization of cytokines were further detected. Furthermore, analyses of hypercoagulable state of the blood were also performed.

RESULTS

Treatment with CYR increased the average number of implantation sites, promoted angiogenesis in endometrial, and regulated monocytes/macrophages and the cytokine levels. Moreover, CYR downregulated the overexpression of D-dimer and fgl2 after ovarian hyperstimulation.

CONCLUSION

CYR facilitates embryo implantation by alleviating ovarian hyperstimulation, promoting endometrial decidualization and angiogenesis, regulating macrophage polarization, and reversing the hypercoagulable state of the blood.

Ovarian Stimulation in Mice Resulted in Abnormal Placentation through Its Effects on Proliferation and Cytokine Production of Uterine NK Cells

Ovarian stimulation is associated with an increased incidence of abnormal placentation. Uterine natural killer (uNK) cells are the major subpopulation of decidual immune cells, which are crucial for placentation. In a previous study, we found that ovarian stimulation impairs uNK cell density on gestation day (GD) 8.5 in mice. However, it was not clear how ovarian stimulation led to a reduction in the density of uNK cells. In this study, we constructed two mouse models, an in vitro mouse embryo transfer model and an estrogen-stimulated mouse model. We used HE and PAS glycogen staining, immunohistochemical techniques, q-PCR, Western blot, and flow cytometry to analyze the mouse decidua and placenta, and the results showed that SO resulted in a fetal weight reduction, abnormal placental morphology, decreased placental vascular density, and abnormal density and function of uNK cells. Our results suggest that ovarian stimulation resulted in aberrant estrogen signaling and may contribute to the disorder of uNK cells caused by ovarian stimulation. Together, these results provide new insights into the mechanisms of aberrant maternal endocrine environments and abnormal placentation.

Ameliorative Effect of Citrus Lemon Peel Extract and Resveratrol on Premature Ovarian Failure Rat Model: Role of iNOS/Caspase-3 Pathway

Premature ovarian failure (POF) is described as a loss of oocytes and the absence of folliculogenesis and is considered an adverse effect of chemotherapeutic drugs, which leads to infertility. Subsequently, the existing inquiry was achieved by exploring the potential suspicious influences of lemon peel extract (LPE), and resveratrol (RES) on cyclophosphamide (CPA) induced-POF. The results showed that CPA-induced POF significantly decreased serum estradiol (E2) and progesterone levels, along with a considerable rise in serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels. Moreover, CPA administration to rats significantly increased the serum level of Malondialdehyde (MDA) and significantly lowered the levels of reduced glutathione (GSH) and superoxide dismutase (SOD); in addition, it increased nuclear factor kappa B (NF-κB) levels, tumor necrosis factor-α (TNF-α), as well as cyclooxygenase 2 (COX-2) with the spread expression of inducible nitric oxide synthase (iNOS) mRNA levels and caspase-3 (Casp3) levels in ovarian tissues versus the control rats. However, treatment with LPE and RES suppressed the triggering of NF- κB pathways, evidenced by a considerable reduction in Casp3 & iNOS mRNA expression level and significant ameliorative effects in all evaluated parameters, as confirmed by the histological and immunohistochemical investigation when comparing the model group. In overall findings, both lemon peel extract and resveratrol can mitigate the adverse effects of CPA-induced POF. Most crucially, its combination therapy is a promising pharmacological agent for this disease.

Use of anti-inhibin monoclonal antibody for increasing the litter size of mouse strains and its application to i-GONAD

The litter size of mouse strains is determined by the number of oocytes naturally ovulated. Many attempts have been made to increase litter sizes by conventional superovulation regimens (e.g., using equine or human gonadotropins, eCG/hCG but had limited success because of unexpected decreases in the numbers of embryos surviving to term. Here, we examined whether rat-derived anti-inhibin monoclonal antibodies (AIMAs) could be used for this purpose. When C57BL/6 female mice were treated with an AIMA and mated, the number of healthy offspring per mouse increased by 1.4-fold (11.9 vs. 8.6 in controls). By contrast, treatment with eCG/hCG or anti-inhibin serum resulted in fewer offspring than in nontreated controls. The overall efficiency of production based on all females treated (including nonpregnant ones) was improved 2.4 times with AIMA compared with nontreated controls. The AIMA treatment was also effective in ICR mice, increasing the litter size from 15.3 to 21.2 pups. We then applied this technique to an in vivo genome-editing method (improved genome-editing via oviductal nucleic acid delivery, i-GONAD) to produce C57BL/6 mice deficient for tyrosinase. The mean litter size following i-GONAD increased from 4.8 to 7.3 after the AIMA treatment and genetic modifications were confirmed in 80/88 (91%) of the offspring. Thus, AIMA treatment is a promising method for increasing the litter size of mice and may be applied for the easy proliferation of mouse colonies as well as in vivo genetic manipulation, especially when the mouse strains are sensitive to handling.

Time from trophectoderm biopsy to vitrification affects the developmental competence of biopsied blastocysts

Purpose

The present study aimed to examine the correlations of the time interval from trophectoderm (TE) biopsy to vitrification with the blastocyst survival rate and blastocyst outgrowth ability.

Methods

A total of 1,202 mouse blastocysts were randomly divided into control (non-biopsy) and TE biopsy groups. The biopsied blastocysts were vitrified at various time points. The survival rate after warming, blastocyst adhesion rate, and outgrowth area was investigated. Several biopsied blastocysts were cultured in a time-lapse incubator, and the time required for re-expansion was measured.

Results

Blastocyst survival rates after warming and blastocyst adhesion rates were comparable between the control and biopsy groups. The area of trophoblast outgrowth in the 1-h biopsy group was significantly smaller than that in the control, 0-h biopsy, and 4-h biopsy groups (p = 0.0304, p = 0.0058, and p = 0.0029, respectively). Re-expansion of blastocysts was observed at a high incidence 1-2 h after TE biopsy.

Conclusions

The vitrification of biopsied blastocysts in the process of re-expansion impairs outgrowth competence; therefore, blastocyst vitrification should be performed immediately after TE biopsy and before initiation of re-expansion.

Ovarian stimulation reduces fetal growth by dysregulating uterine natural killer cells in mice

Ovarian stimulation is associated with a higher risk of low birth weight. However, the precise mechanisms by which ovarian stimulation increases the chances of low birth weight remain unclear. In this mouse model study, in vivo developed blastocysts that were not exposed to gonadotropins were transferred into pseudopregnant females that had mated naturally (the control group), pseudopregnant females that had been administered a low dose of ovulation-stimulating hormone (the L-SO group) and pseudopregnant females that had been administered a high dose of ovulation-stimulating hormone (the H-SO group). The embryo implantation rate and fetal weight were significantly lower in the L-SO and H-SO groups than in the control group. The density of Dolichos biflorus agglutinin (DBA)⁺ uterine natural killer (uNK) cells in the decidua basalis was significantly lower in the L-SO and H-SO groups than in the control group. Ovarian stimulation also downregulated a variety of cytokines related to uNK cells that are involved in placental angiogenesis and trophoblast invasion. Collectively, our findings indicate that ovarian stimulation impairs DBA⁺ uNK cell density in the decidua basalis, which may downregulate uNK-related cytokine secretion and influence placental angiogenesis and restrict fetal growth in mice.

Superovulation with human chorionic gonadotropin (hCG) trigger and gonadotropin releasing hormone agonist (GnRHa) trigger differentially alter essential angiogenic factors in the endometrium in a mouse ART model†

Gonadotropin-releasing hormone agonists (GnRHa) are used as an alternative to human chorionic gonadotropin (hCG) to trigger ovulation and decrease the risk of ovarian hyperstimulation syndrome. GnRHa is less potent at inducing ovarian vascular endothelial growth factor (VEGF), but may also affect endometrial angiogenesis and early placental development. In this study, we explore the effect of superovulation on endometrial angiogenesis during critical periods of gestation in a mouse model. We assigned female mice to three groups: natural mating or mating following injection with equine chorionic gonadotropin and trigger with GnRHa or hCG trigger. Females were killed prior to implantation (E3.5), post-implantation (E7.5), and at midgestation (E10.5), and maternal serum, uterus, and ovaries were collected. During peri-implantation, endometrial Vegfr1 and Vegfr2 mRNA were significantly increased in the GnRHa trigger group (P < 0.02) relative to the hCG group. Vegfr1 is highly expressed in the endometrial lining and secretory glands immediately prior to implantation. At E7.5, the ectoplacental cone expression of Vegfa and its receptor, Vegfr2, was significantly higher in the hCG trigger group compared to the GnRHa group (P < 0.05). Soluble VEGFR1 and free VEGFA were much higher in the serum of mice exposed to the hCG trigger compared to GnRHa group. At midgestation, there was significantly more local Vegfa expression in the placenta of mice triggered with hCG. GnRHa and hCG triggers differentially disrupt the endometrial expression of key angiogenic factors during critical periods of mouse gestation. These results may have significant implications for placental development and neonatal outcomes following human in vitro fertilization.

A Histopathological Evaluation of Ovarian Hyperstimulation Syndrome on Reproductive and Vital Organs and the Role of the VEGF-PKA Pathway in a Mouse Model

Ovarian hyperstimulation syndrome (OHSS) is one of the most common and iatrogenic complications of in vitro fertilization therapy, which is an exaggerated response to excess hormones resulting in the development of a large number of maturing follicles. Although the complications of and reasons for the condition are well known, the overall histopathological effects on systemic organs and the extent of the damage have not been fully elucidated. Besides, the mechanism that underlies the situation is not very well known. The aim of the present work was to analyse the histopathological effects of OHSS on reproductive (uterus and ovary) and vital organs (liver and kidney) and the possible role of the VEGF-PKA pathway in triggering the condition. Balb/c mice were used to establish an OHSS model. The OHSS group were injected with overdose PMSG while the normal responder group were injected with an optimal dose. Histopathological evaluation was utilised in the liver, kidney, ovary, and uterus stained with hematoxylin and eosin, Masson's trichrome, and periodic acid-Schiff stain. The expression profiles of VEGF (vascular endothelial growth factor), PKA (protein kinase A), and p-PKA (an activated form of PKA) were detected with immunohistochemistry and Western blotting. OHSS was demonstrated to have a negative histopathological effect on all of the organs analysed. These effects were associated with an overall increase in the expression levels of VEGF, PKA, and p-PKA. OHSS has a serious histopathological negative effect on the systemic and reproductive organs and is proven to affect overall health, and thus should be considered a dangerous complication during ART techniques. The activation of the VEGF-PKA pathway, which is indicated by the expression levels of VEGF, PKA, and p-PKA, is demonstrated to accompany this complication, which should be further elucidated to understand the mechanisms underlying the condition.

Perinatal outcomes of neonates born from different endometrial preparation protocols after frozen embryo transfer: a retrospective cohort study

BACKGROUND

Previous studies have focused on pregnancy outcomes after frozen embryo transfer (FET) performed using different endometrial preparation protocols. Few studies have evaluated the effect of endometrial preparation on pregnancy-related complications. This study was designed to explore the association between different endometrial preparation protocols and adverse obstetric and perinatal complications after FET.

METHODS

We retrospectively included all FET cycles (n = 12,950) in our hospital between 2010 and 2017, and categorized them into three groups, natural cycles (NC), hormone replacement therapy (HRT) and ovarian stimulation (OS) protocols. Pregnancy-related complications and subsequent neonatal outcomes were compared among groups.

RESULTS

Among all 12,950 FET cycles, the live birth rate was slightly lower for HRT cycles than for NC (HRT vs. NC: 28.15% vs. 31.16%, p < 0.001). The pregnancy loss rate was significantly higher in OS or HRT cycles than in NC (HRT vs. NC: 17.14% vs. 10.89%, p < 0.001; OS vs. NC: 16.44% vs. 10.89%, p = 0.001). Among 3864 women with live birth, preparing the endometrium using OS or HRT protocols increased the risk of preeclampsia, and intrahepatic cholestasis of pregnancy (ICP) in both singleton and multiple deliveries. Additionally, OS and HRT protocols increased the risk of low birth weight (LBW) and small for gestational age (SGA) in both singletons and multiples after FET.

CONCLUSION

Compared with HRT or OS protocols, preparing the endometrium with NC was associated with the decreased risk of pregnancy-related complications, as well as the decreased risk of LBW and SGA after FET.

Effects of fatty acid supplementation during vitrification and warming on the developmental competence of mouse, bovine and human oocytes and embryos

RESEARCH QUESTION

Does fatty acid supplementation in vitrification and warming media influence developmental competence in oocytes after vitrification and warming?

DESIGN

Mouse oocytes and four-cell embryos were vitrified and warmed with solutions supplemented with fatty acid and cultured to the blastocyst stage. To study lipid metabolism after vitrification, quantitative real-time polymerase chain reaction was used to analyse the expression of genes related to beta oxidation in mouse embryos vitrified and warmed with or without fatty acids. The effects of fatty acid supplementation in the warming solutions on the developmental competence of bovine and human embryos were analysed. Blastocyst outgrowth assay was used to evaluate the potential of human blastocysts for adhesion to fibronectin.

RESULTS

The neutral lipid content of mouse oocytes in the fatty acid 1% supplementation group was significantly higher than in the fatty acid 0% group (P = 0.0032). The developmental rate to the blastocyst stage was significantly higher in the fatty acid 1% group than in the fatty acid 0% group in mice (P = 0.0345). Fatty acid supplementation in warming solution upregulated Acaa2 and Hadha in mouse embryos. Fatty acids significantly improved the developmental ability of bovine embryos to the blastocyst stage (P = 0.0048). Warming with 1% fatty acid supplementation significantly increased the proportion of human blastocysts with morphological grade A inner cell mass (P = 0.0074) and trophectoderm (P = 0.0323).

CONCLUSIONS

Fatty acid supplementation in the warming solutions improved the developmental competence of vitrified-warmed mouse oocytes by activating the beta-oxidation pathway. Fatty acid supplementation enhanced the developmental rate of bovine embryos to the blastocyst stage and improved morphological characteristics of human embryos vitrified at the cleavage stage.

Embryo Morphokinetics and Blastocyst Development After GnRH Agonist versus hCG Triggering in Normo-ovulatory Women: a Secondary Analysis of a Multicenter Randomized Controlled Trial

Gonadotropin-releasing hormone agonist (GnRHa) for final oocyte maturation, along with vitrification of all usable embryos followed by transfer in a subsequent frozen-thawed cycle, is the most effective strategy to avoid ovarian hyperstimulation syndrome (OHSS). However, less is known about the ovulation induction triggers effect on early embryo development and blastocyst formation. This study is a secondary analysis of a multicenter, randomized controlled trial, with the aim to compare embryo development in normo-ovulatory women, randomized to GnRHa or human chorionic gonadotropin (hCG) trigger. In all, 4056 retrieved oocytes were observed, 1998 from the GnRHa group (216 women) and 2058 from the hCG group (218 women). A number of retrieved oocytes, mature and fertilized oocytes, and high-quality embryos and blastocysts were similar between the groups. A sub-analysis in 250 women enrolled at the main trial site including 2073 oocytes was conducted to compare embryo morphokinetics and cleavage patterns with EmbryoScope time-lapse system. In total, 1013 oocytes were retrieved from the GnRHa group (124 women) and 1060 oocytes were retrieved from the hCG group (126 women). Morphokinetic parameters and cleavage patterns were comparable between the groups. However, embryos derived from the GnRHa group were less likely to perform rolling during their development than the embryos from the hCG trigger group (OR = 0.41 (95%CI 0.25; 0.67), p-value 0.0003). The comparable results on embryo development and utilization rates between the GnRHa and hCG triggers is of clinical relevance to professionals and infertile patients, when GnRHa trigger and freeze-all is performed to avoid OHSS development. ClinicalTrials.gov Identifier: NCT02746562.

Premature ovarian insufficiency: pathogenesis and therapeutic potential of mesenchymal stem cell

Primary ovarian insufficiency (POI) is defined as a reduction in ovarian function before the expected age of menopause. POI is known to increase the risk of cardiovascular disorders, osteoporosis, cognitive decline, and mood disorders, resulting in a reduced quality of life. Appropriate hormone replacement for premenopausal women decreases these adverse health risks and improves quality of life for women with POI, but does not prolong life expectancy. The potential etiologies of POI include chromosomal abnormalities and genetic mutations, autoimmune factors, and iatrogenic causes, including surgery, chemotherapy, and radiation therapy. A major association is suggested to exist between reproductive longevity and the DNA damage pathway response genes. DNA damage and repair in ovarian granulosa cells is strongly associated with POI. Depletion of oocytes with damaged DNA occurs through different cell death mechanisms, such as apoptosis, autophagy, and necroptosis, mediated by the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/forkhead transcription factors 3 (FOXO3) pathway. Mesenchymal stem cells (MSCs) are characterized by the ability of self-renewal and differentiation and play an important role in the regeneration of injured tissues. Transplantation of MSCs has been shown to functionally restore ovarian reserve in a POI mouse model. Recent advances in stem cell therapy are likely to be translated to new therapeutic options bringing new hope to patients with POI. The aim of this review is to summarize the pathogenic mechanisms that involve cell death and DNA damage and repair pathways and to discuss the stem cell-based therapies as potential therapeutic options for this gynecologic pathology.

Effect of HCG-Triggered Ovulation on Pregnancy Outcomes in Intrauterine Insemination: An Analysis of 5,610 First IUI Natural Cycles With Donor Sperm in China

Objective: To evaluate the effect of human chorionic gonadotropin (hCG) trigger ovulation on pregnancy outcomes in natural IUI cycles with donor sperm. Methods: This retrospective cohort study included 5,610 first-natural IUI cycles with donor sperm in infertile couples during the period from January 2012 to December 2017. To control for other confounding factors, our analysis was restricted to normo-ovulatory women without tubal infertility. The main outcome measure was live birth rate; the secondary outcomes included rates of clinical pregnancy and miscarriage. Results: In the crude analysis, both the clinical pregnancy (27.40 vs. 22.73%; P = 0.001) and live birth rates (24.52 vs. 20.13%; P = 0.007) were significantly higher for the hCG group than for the spontaneous LH group. After adjustment for a number of confounding factors, the reproductive outcomes were still significantly worse for the spontaneous ovulatory group. Conclusions: Among women undergoing natural cycle IUI with donor sperm, hCG triggered ovulation for timing insemination offers beneficial impacts on both clinical pregnancy rates and live birth rates.

Ovarian damage from chemotherapy and current approaches to its protection

BACKGROUND

Anti-cancer therapy is often a cause of premature ovarian insufficiency and infertility since the ovarian follicle reserve is extremely sensitive to the effects of chemotherapy and radiotherapy. While oocyte, embryo and ovarian cortex cryopreservation can help some women with cancer-induced infertility achieve pregnancy, the development of effective methods to protect ovarian function during chemotherapy would be a significant advantage.

OBJECTIVE AND RATIONALE

This paper critically discusses the different damaging effects of the most common chemotherapeutic compounds on the ovary, in particular, the ovarian follicles and the molecular pathways that lead to that damage. The mechanisms through which fertility-protective agents might prevent chemotherapy drug-induced follicle loss are then reviewed.

SEARCH METHODS

Articles published in English were searched on PubMed up to March 2019 using the following terms: ovary, fertility preservation, chemotherapy, follicle death, adjuvant therapy, cyclophosphamide, cisplatin, doxorubicin. Inclusion and exclusion criteria were applied to the analysis of the protective agents.

OUTCOMES

Recent studies reveal how chemotherapeutic drugs can affect the different cellular components of the ovary, causing rapid depletion of the ovarian follicular reserve. The three most commonly used drugs, cyclophosphamide, cisplatin and doxorubicin, cause premature ovarian insufficiency by inducing death and/or accelerated activation of primordial follicles and increased atresia of growing follicles. They also cause an increase in damage to blood vessels and the stromal compartment and increment inflammation. In the past 20 years, many compounds have been investigated as potential protective agents to counteract these adverse effects. The interactions of recently described fertility-protective agents with these damage pathways are discussed.

WIDER IMPLICATIONS

Understanding the mechanisms underlying the action of chemotherapy compounds on the various components of the ovary is essential for the development of efficient and targeted pharmacological therapies that could protect and prolong female fertility. While there are increasing preclinical investigations of potential fertility preserving adjuvants, there remains a lack of approaches that are being developed and tested clinically.

Effects of gonadotropin administration on clinical outcomes in clomiphene citrate-based minimal stimulation cycle IVF

PURPOSE

Exogenous gonadotropins (EGn) have been used occasionally in clomiphene citrate (CC)-based minimal stimulation cycles to compensate insufficient secretion of endogenous gonadotropin; however, the effectiveness of EGn supplementation remains unknown. In the present study, we assessed whether EGn improved pregnancy outcomes in CC-based minimal stimulation cycles.

METHODS

A total of 223 patients treated with CC and EGn (CC-EGn group) were matched one to one to patients treated with CC only (CC group) by propensity score matching. Embryonic and pregnancy outcomes were retrospectively compared between the groups.

RESULTS

The numbers of retrieved oocytes, fertilized oocytes, cleaved embryos, and cryopreserved blastocysts were increased in the CC-EGn group compared with the CC group. However, the cumulative live birthrate was comparable between the two groups. Although the increased number of retrieved oocytes was correlated significantly with improvement of the cumulative live birthrate in both groups, the correlation tended to be lower in the CC-EGn group than in the CC group (odds ratio, 1.193 vs 1.553).

CONCLUSIONS

In CC-based minimal stimulation cycles, the stimulation should be started with CC only, and EGn administration should be scheduled only if insufficient secretion of endogenous gonadotropin is observed in the late follicular phase.

Dynamic Expression of Interleukin-33 and ST2 in the Mouse Reproductive Tract Is Influenced by Superovulation

Interleukin-33 (IL-33) is an IL-1 family cytokine with pleiotropic effects on diverse cell types. Dysregulated IL-33 signaling has been implicated in pregnancy-related disorders, including preeclampsia and recurrent pregnancy loss, and in ovarian function in women undergoing controlled ovarian stimulation for in vitro fertilization. To date, expression of IL-33 and its receptor subunit, ST2, in the female reproductive tract remains poorly characterized. We identify IL-33-expressing oocytes surrounded by ST2-expressing granulosa cells at all stages of follicular development, in addition to IL-33⁺ and ST2⁺ non-endothelial cells in the ovarian stroma and theca layer in ovaries from adult mice. These expression patterns are similar in estrus- and diestrus-stage adults and in pubescent mice, suggesting a role for IL-33 signaling in ovarian function throughout development and in the estrous cycle. In the uterus, we find expression of IL-33 and ST2 in glandular and luminal epithelia during estrus and at the initiation of pregnancy. Uterine IL-33 expression was modulated by the estrous cycle and was reduced in pubescent females. Last, superovulation increases transcripts for IL-33 and the soluble form of ST2 (sST2) in ovaries, and for IL-33 in uteri. Collectively, our findings lay the foundation for studies identifying cell type-specific requirements for IL-33/ST2 signaling in the establishment and maintenance of mouse pregnancy.

Evaluation of uterine receptivity after gonadotropin releasing hormone agonist administration as an oocyte maturation trigger: a rodent model

In natural cycle or minimal stimulation cycle IVF, buserelin acetate (buserelin), a gonadotropin-releasing hormone agonist, is often used as a maturation trigger; however, its effect on pregnancy outcomes remains unclear. Therefore, in the present study, we compared uterine receptivity in buserelin-administered mice with that in human chorionic gonadotropin (hCG)-administered mice during the peri-implantation period. Implantation, decidualisation, and term-pregnancy were impaired following hCG, but not buserelin administration. hCG stimulated the synthesis and secretion of progesterone and oestradiol, whereas ovarian steroidogenesis in the buserelin-treated group was comparable with that in the control group. Furthermore, similar to the observation in controls, the buserelin-treated group exhibited activation of progesterone receptor signalling and inhibition of oestrogen receptor signalling in the endometrial epithelium on the day of implantation. However, epithelial progesterone signalling was not detected, and a high expression of genes downstream to oestrogen was observed on day 4 following hCG administration. These results suggest that buserelin administration does not impact uterine receptivity as it did not affect ovarian steroidogenesis and endometrial steroid signalling. Therefore, buserelin is preferred as an oocyte maturation trigger to optimise uterine receptivity during treatments involving timed intercourse, intrauterine insemination, or fresh embryo transfer following in vitro fertilisation.

Effects of Intrauterine Air Bubbles on Embryonic Development in Mice

During murine embryo transfer, air bubbles frequently are loaded with embryos into the transfer catheter, but the role of air bubbles on embryonic development is unclear. This study shows that intrauterine air disrupted embryo spacing, induced deciduoma, and impaired postimplantation development. RNA sequencing showed that the gene expression profile of air-induced deciduoma differed significantly from that of embryo-induced decidua but is similar to tetraploid-induced deciduoma. A subset of 33 common genes was upregulated in the embryo-induced decidua compared with air- or tetraploid-induced deciduoma. These data suggest that the inner cell mass (ICM) plays a key role in regulating decidualization and that the trophectoderm is an intermediate that relays ICM-derived signals to other target cells. Our results may provide an innovative approach for detecting the developmental status of embryos in human reproductive medicine.

Electroacupuncture facilitates implantation by enhancing endometrial angiogenesis in a rat model of ovarian hyperstimulation

Controlled ovarian hyperstimulation (COH) impairs the synchronized development of endometrium and embryo, resulting in the failure of embryo implantation. Here, we investigated what effects electroacupuncture had on embryo implantation in COH rats. Female rats were randomly assigned to four groups: normal (N), model (M), electroacupuncture (EA), and electroacupuncture pretreatment (PEA). Rats in groups M, EA, PEA were injected with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin to establish the COH model. Rats in group EA received electroacupuncture treatment from the PMSG injection day to the 3rd day of pregnancy (D3), while those in group PEA received electroacupuncture treatment for 3 days before the PMSG day and continuing to D3. Furthermore, another 30 female rats who received the same treatment as the rats in group PEA were injected with siVEGFR2 into uterine lumen. The endometrial microvascular density (MVD) and the expression levels of vascular endothelial growth factor-A, angiopoietin-1, and fibroblast growth factor-2 were significantly lower in groups M than in groups N and PEA. The percentage of dolichos biflorus agglutinin positive uterine natural killer cells in groups N, EA and PEA was higher than that in group M. After the siVEGFR2 injection, the protein expression levels of vascular endothelial growth factor receptor 2 (VEGFR2), PI3K, p-AKT and p-ERK, the embryo number and the MVD were significantly reduced. In conclusion, electroacupuncture can facilitate embryo implantation in COH rats by activating the VEGFR2/PI3K/AKT and VEGFR2/ERK signaling pathways which have a positive relationship with endometrial angiogenesis.

Bushen Huoxue Recipe Alleviates Implantation Loss in Mice by Enhancing Estrogen-Progesterone Signals and Promoting Decidual Angiogenesis Through FGF2 During Early Pregnancy

Bushen Huoxue recipe (BSHXR) is a classic Chinese herbal prescription for nourishing the kidney and activating blood circulation. It consists of six herbs: Astragali radix, Angelicae sinensis radix, Ligustici Chuanxiong Rhizoma, Cuscutae semen, Taxilli Herba, and Dipsaci Radix, and the main active constituents of BSHXR are ferulic acid, calycosin-7-glucopyranoside, hyperoside, quercitrin, and asperosaponin VI. In clinical practice, BSHXR is traditionally used to treat failed pregnancy and its complications. However, little is known about the underlying mechanism of BSHXR for the treatment of implantation loss during early pregnancy. In the current study, controlled ovarian hyperstimulation was induced in mice as our implantation loss model, and we evaluated the effects of BSHXR on implantation, decidualization, decidual angiogenesis, and reproductive outcome. We showed that BSHXR could regulate the supraphysiological levels of serum estrogen and progesterone observed in these mice, and also act on estrogen and progesterone receptors in the stroma and epithelium. BSHXR also enhanced FGF2 expression in the vascular sinus folding area of the decidua, thus potentially reducing implantation loss during early pregnancy and contributing to placentation and survival of the fetuses. Taken together, our findings provide scientific evidence for the application of BSHXR in the clinic as a treatment for implantation loss during early pregnancy, and warrant further investigation of BSHXR as an effective treatment for failed pregnancy and its complications.

The superovulated environment, independent of embryo vitrification, results in low birthweight in a mouse model

Epidemiological studies suggest that babies born following in vitro fertilization (IVF) and fresh embryo transfer are of lower birthweight than babies born following frozen embryo transfer, although the mechanism responsible for this phenotype is not known. We developed a novel mouse model that isolates the independent effects of embryo freezing and the superovulated environment, which cannot be performed in humans. We transferred blastocysts that had been vitrified and warmed, mixed with with fresh blastocysts, into individual pseudopregnant recipients produced by either natural mating or mating following injection with equine chorionic gonadotropin and human chorionic gonadotropin and hCG (superovulation). We found that superovulation of the recipient dams led to significantly lower fetal weight at term while blastocyst vitrification had no significant effect on fetal weight (1.43 ± 0.24 g fresh-natural, 1.30 ± 0.28 g vitrified-natural vs. 1.09 ± 0.20 fresh-superovulated, 0.93 ± 0.23 g vitrified-superovulated, P < 0.0001). Doppler ultrasound revealed increased median umbilical artery resistance in the placentae of near-term dams exposed to superovulation compared to naturally mated dams (0.927 vs 0.904, P = 0.02). Additionally, placental microvascular density was lower in superovulated compared to naturally mated dams (1.24 × 10-3 vessel/micron vs 1.46 × 10-3 vessels/micron, P = 0.046). Gene expression profiling suggested alterations in fetal genes involved in glucorticoid regulation. These results suggest a potential mechanism for altered birthweight following superovulation in our model and may have implications for human IVF.

Comparison of pregnancy outcomes following fresh and electively frozen single blastocyst transfer in natural cycle and clomiphene-stimulated IVF cycles

STUDY QUESTION

Are there any differences in live birth rates (LBR) following fresh blastocyst transfer in natural or clomiphene-stimulated cycles, or after elective blastocyst freezing in clomiphene-stimulated cycles followed by thawing and transfer at different time-points?

SUMMARY ANSWER

Clomiphene citrate (CC) administration adversely affected the LBR after single fresh blastocyst transfer (SBT) in CC cycles compared with that in natural cycles, while this adverse effect of CC is not present when a single vitrified-warmed blastocyst transfer (SVBT) is performed in subsequent natural ovulatory cycles, regardless of the duration between CC administration and the day of SVBT.

WHAT IS KNOWN ALREADY

CC affects uterine receptivity associated with a thinning of the uterine endometrium through an antioestrogenic effect. However, the duration that this adverse effect of CC on uterine endometrium persists after initial use is still unknown.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study of 157 natural cycle IVFs followed by SBT and 1496 minimal ovarian stimulation with CC IVF cycles followed by SBT (n = 24) or SVBT (n = 1472) from January 2010 to December 2014 was conducted. SVBT cycles were classified into two groups according to the period between the last day of CC administration and the day of SVBT (A: ≤60 d and B: ≥61 d). All groups were then compared based on pregnancy outcomes (natural-SBT group: n = 157, CC-SBT group: n = 24, SVBT-A: n = 1143, SVBT-B: n = 329).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women were aged 30–39 years at oocyte retrieval. In SVBT cycles, blastocysts were vitrified and warmed using a Cryotop safety kit. SVBT was performed in subsequent natural ovulatory cycles. The main outcomes were LBR and neonatal outcome, and both were compared among the groups.

MAIN RESULTS AND THE ROLE OF CHANCE

The LBR in the CC-SBT group (29.2%, 7/24) was significantly lower compared with the natural-SBT (56.1%, 88/157) (P = 0.01) and SVBT-A (50.0%, 572/1143) (P = 0.04), but not SVBT-B (47.4%, 156/329), groups. Furthermore, multivariate logistic regression analysis revealed that the LBR was comparable among the natural-SBT and SVBT groups, but was significantly lower in the CC-SBT group (adjusted odds ratio: 0.324, 95% CI: 0.119–0.800, P = 0.01). No significant differences among all groups were observed for gestational age (P = 0.19), birthweight (P = 0.41) and incidence of malformation (P = 0.53).

LIMITATIONS, REASONS FOR CAUTION

In this study we analysed a biased sample, based on clinical judgement regarding endometrial thickness, and the study was limited by its retrospective nature. The low statistical power caused by the group size disparity was also a limitation, especially in the CC-SBT group. Although the outcome showing inferiority of CC-SBT compared to natural-SBT is consistent with general findings in the literature, further large-scale clinical studies, ideally RCTs, are necessary to validate our results and clarify the prolonged effect of CC in SVBT cycles on pregnancy and neonatal outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our observation suggests that CC administered in minimal ovarian stimulation cycles affects adversely the pregnancy outcomes when SBT is performed. Therefore, for a CC-based minimal stimulation IVF cycle, we suggest that frozen embryo transfer should be performed in a subsequent natural ovulatory cycle to avoid the possibility of implantation failure associated with CC administration.

STUDY FUNDING/COMPETING INTERESTS

The authors have no conflicts of interest to declare. No external funding was either sought or obtained.

Roles of DEK in the endometrium of mice in early pregnancy

Embryo implantation is a complex process requiring reciprocal interactions between implantation-competent blastocysts and receptive uteri. Accumulating evidence from Digital Protein Expression Profiling indicates that DEK protein expression at implantation sites (ISs) was much higher than that at inter-implantation sites (IISs). In this study, we investigated the expression of DEK in mouse uterus by immunohistochemistry (IHC), Western blotting. We explored its function during decidualization of uterine stromal cells by inhibiting the expression of DEK. In further study of mechanism, the cell proliferation, apoptosis and DNA damage were detected after inhibiting DEK during decidualization of stromal cells. The results suggest that DEK participates in decidualization of stromal cells through mediating cell proliferation, apoptosis and DNA repair.

Efficient and scheduled production of pseudopregnant female mice for embryo transfer by estrous cycle synchronization

In embryo transfer experiments in mice, pseudopregnant females as recipients are prepared by sterile mating with vasectomized males. Because only females at the proestrus stage accept males, such females are selected from a stock of animals based on the appearance of their external genital tract. Therefore, the efficiency of preparing pseudopregnant females largely depends on the size of female colonies and the skill of the operators who select females for sterile mating. In this study, we examined whether the efficiency of preparing pseudopregnant females could be improved by applying an estrous cycle synchronization method by progesterone (P4) pretreatment, which significantly enhances the superovulation outcome in mice. We confirmed that after two daily injections of P4 (designated Days 1 and 2) in randomly selected females, the estrous cycles of most females (about 85%) were synchronized at metestrus on Day 3. When P4-treated females were paired with vasectomized males for 4 days (Days 4–8), a vaginal plug was found in 63% (20/32) of the females on Day 7. After the transfer of vitrified-warmed embryos into their oviducts, 52% (73/140) of the embryos successfully developed into offspring, the rate being comparable to that of the conventional embryo transfer procedure. Similarly, 77% (24/31) of females became pregnant by fertile mating with intact males for 3 days, which allowed the scheduled preparation of foster mothers. Thus, our estrous cycle synchronization method may omit the conventional experience-based process of visually observing the vagina to choose females for embryo transfer. Furthermore, it is expected that the size of female stocks for recipients can be reduced to less than 20%, which could be a great advantage for facilities/laboratories undertaking mouse-assisted reproductive technology.

Nausea and vomiting of pregnancy - What's new?

Nausea and vomiting of pregnancy (NVP) is one of the most common disorders of pregnancy. The symptoms occur predominantly during the first trimester, although in a subgroup of patients they can continue throughout the entire pregnancy and can affect the woman's quality of life. A small percentage of women develop a severe form of NVP called hyperemesis gravidarum (HG) that if left untreated may lead to significant maternal morbidity and adverse birth outcomes. Overall, the morbidity in pregnant women with NVP is significant, although it tends to be underestimated. The pathogenesis of NVP remains unclear, but there is consensus that the disorder is multifactorial and that various genetic, endocrine and infectious factors may be involved. The treatment of NVP can be challenging as the optimal targets for therapy are not known. Currently, the therapy used depends on the severity of the disorder and it is focused on improving the symptoms while minimizing risks to mother and fetus. Therapies range from dietary changes, pharmacologic treatment or hospitalization with intravenous fluid replacement and nutrition therapy. The aims of this review are 1) to provide an overview of NVP, 2) to present possible links between the most important factors associated with the pathogenesis of NVP and 3) to discuss the effectiveness and safety of the pharmacologic and non-pharmacologic options available to treat this disorder.

Preparation of endometrium for frozen embryo replacement cycles: a systematic review and meta-analysis

PURPOSE

The purpose of this study was to evaluate the best protocol to prepare endometrium for frozen embryo replacement (FER) cycles.

METHODS

This study is a systematic review and meta-analysis. Following PubMed and OvidSP search, a total of 1166 studies published after 1990 were identified following removal of duplicates. Following exclusion of studies not matching our inclusion criteria, a total of 33 studies were analyzed. Primary outcome measure was live birth. The following protocols, including true natural cycle (tNC), modified natural cycle (mNC), artificial cycle (AC) with or without suppression, and mild ovarian stimulation (OS) with gonadotropin (Gn) or aromatase inhibitor (AI), were compared.

RESULTS

No statistically significant difference for both clinical pregnancy and live birth was noted between tNC and mNC groups. When tNC and AC without suppression groups are compared, there was a statistically significant difference in clinical pregnancy rate in favor of tNC, whereas it failed to reach statistical significance for live birth. When tNC and AC with suppression groups are compared, there was a statistically significant difference in live birth rate favoring the latter. Similar pregnancy outcome was noted among mNC versus AC with or without suppression groups. Similarly, no difference in clinical pregnancy and live birth was noted when ACs with or without suppression groups are compared.

CONCLUSIONS

There is no consistent superiority of any endometrial preparation for FER. However, mNC has several advantages (being patient-friendly; yielding at least equivalent or better pregnancy rates when compared with tNC and AC with or without suppression; may not require LPS). Mild OS with Gn or AI may be promising.

Genome-wide association study reveals novel variants for growth and egg traits in Dongxiang blue-shelled and White Leghorn chickens

This study was designed to investigate the genetic basis of growth and egg traits in Dongxiang blue-shelled chickens and White Leghorn chickens. In this study, we employed a reduced representation sequencing approach called genotyping by genome reducing and sequencing to detect genome-wide SNPs in 252 Dongxiang blue-shelled chickens and 252 White Leghorn chickens. The Dongxiang blue-shelled chicken breed has many specific traits and is characterized by blue-shelled eggs, black plumage, black skin, black bone and black organs. The White Leghorn chicken is an egg-type breed with high productivity. As multibreed genome-wide association studies (GWASs) can improve precision due to less linkage disequilibrium across breeds, a multibreed GWAS was performed with 156 575 SNPs to identify the associated variants underlying growth and egg traits within the two chicken breeds. The analysis revealed 32 SNPs exhibiting a significant genome-wide association with growth and egg traits. Some of the significant SNPs are located in genes that are known to impact growth and egg traits, but nearly half of the significant SNPs are located in genes with unclear functions in chickens. To our knowledge, this is the first multibreed genome-wide report for the genetics of growth and egg traits in the Dongxiang blue-shelled and White Leghorn chickens.

Administering human chorionic gonadotropin injections for triggering follicle maturation could impact fertility during the subsequent menstrual cycle

OBJECTIVE

To determine whether the use of a human chorionic gonadotropin (hCG) injection as a follicle-maturation trigger affects a patient's reproductive ability during their subsequent menstrual cycle.

METHODS

Patients that were infertile undergoing natural-cycle in vitro fertilization at Kato Ladies Clinic, Japan, between March and June 2012 were enrolled in a prospective cohort study. Patients who had received fertility treatments other than hCG injections were excluded from the study. The remaining patients were divided into two cohorts; patients who had received injection-administered hCG (study group) and patients who had not received any fertility treatment (control group) during their preceding menstrual cycle. The rates of oocyte retrieval, fertilization, clinical pregnancy, and live deliveries were analyzed using a Fisher exact test.

RESULTS

The rate of successful oocyte-retrieval (P<0.001) and the delivery-rate (P=0.002) were significantly lower in the study group in comparison with the control group. Additionally, the incidence of empty follicles (P<0.001) and degenerated oocytes (P=0.002) was significantly higher in the exposure group.

CONCLUSION

Triggering follicle maturation with hCG during in vitro fertilization could impact patient fertility during their next cycle. Treatment with hCG injection has the potential to influence not only the cycle during which it is administered, but also the subsequent menstrual cycle.

Frozen-thawed embryo transfer in a natural or mildly hormonally stimulated cycle in women with regular ovulatory cycles: a RCT

STUDY QUESTION

Can ovarian stimulation with low dose hMG improve the implantation rate (IR) per frozen-thawed embryo transferred (FET) when compared with natural cycle in an FET programme in women with a regular ovulatory cycle?

SUMMARY ANSWER

Both IR and live birth rate (LBR) per FET were similar in the group with mild ovarian stimulation and the natural cycle group.

WHAT IS KNOWN ALREADY

Different cycle regimens for endometrial preparation are used prior to FET: spontaneous ovulatory cycles, cycles with artificial endometrial preparation using estrogen and progesterone hormones, and cycles stimulated with gonadotrophins or clomiphene citrate. At present, it is not clear which regimen results in the highest IR or LBR. More specifically, there are no RCTs in ovulatory women comparing reproductive outcome after FET during a natural cycle and during a hormonally stimulated cycle.

STUDY DESIGN, SIZE, DURATION

A total of 410 women scheduled for FET during 579 cycles (December 2003-September 2013) were enrolled in an open-label RCT to natural cycle (NC FET group, n = 291) or to a cycle hormonally stimulated with s.c. gonadotrophins (hMG FET group, 37.5-75 IU per day, n = 288). A total of 672 embryos were transferred during 434 cycles (332 embryos and 213 cycles in the NC FET group; 340 embryos and 221 cycles in the hMG FET group). Assuming a = 0.05 and 80% power, it was calculated that 219 frozen-thawed embryos were required for transfer in each group to demonstrate a difference of 10% in IR.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women were eligible according to the following inclusion criteria: regular ovulatory cycle, female age ≥21 years and ≤45 years, informed consent. FET cycles with preimplantation genetic screening were excluded. The primary outcome was IR per embryo transferred. Secondary outcomes included IR with fetal heart beat (FHB), LBR per embryo transferred and endometrial thickness on the day of hCG administration. Statistical analysis was by intention to treat and controlled for the presence of multiple measures, as eligible women could be randomized in more than one cycle. Chi-square and independent t-test were used to compare categorical and continuous variables. The relative risk (RR) was estimated using a Poisson model with log link. Hierarchical models with random intercepts for patient and cycle were considered to account for clustering of cycles within patients and of embryos within cycles.

MAIN RESULTS AND THE ROLE OF CHANCE

The primary outcome, IR per embryo transferred, was not statistically different between the NC FET group (41/332 (12.35%)) and in the hMG FET group (55/340 (16.18%)) (RR 1.3 (95% confidence interval (CI) 0.9-2.0), P = 0.19). Similarly, the secondary outcome, IR with FHB per embryo transferred, was 34/332 (10.24%) in the NC FET group and 48/340 (14.12%) in the hMG FET group (RR 1.4 (95% CI 0.9-2.1), P = 0.15). The LBR per embryo transferred was 32/332 (9.64%) in the NC FET group and 45/340 (13.24%) in the hMG FET group (RR 1.4 (95% CI 0.9-2.2), P = 0.17). Endometrial thickness was also similar in both groups [8.9 (95% CI 8.7-9.1) in the NC FET group and 8.9 (95% CI 8.7-9.1) in the hMG FET group]. The duration of the follicular phase was significantly shorter (P < 0.001) in the hMG FET group [13.7 days (95% CI 13.2-14.2)] than in the NC FET group [15.4 days (95% CI 14.8-15.9)].

LIMITATIONS, REASONS FOR CAUTION

Randomization of cycles instead of patients; open-label design; relatively long period of recruitment.

WIDER IMPLICATIONS OF THE FINDINGS

Our observation that the IR per embryo transferred is not significantly increased after FET during natural or gonadotrophin stimulated cycle, suggests that the effect of mild hormonal stimulation with gonadotrophins is smaller than what was considered clinically relevant with respect to reproductive outcome after FET. These data suggest that endometrial receptivity is not relevantly improved, but also not impaired after hormonal stimulation with gonadotrophins. Since FET during a natural cycle is cheaper and more patient-friendly, we recommend this regimen as the treatment of choice for women with regular cycles undergoing FET.

TRIAL REGISTRATION NUMBER

clinicaltrials.gov NCT00492934.

TRIAL REGISTRATION DATE

26 June 2007.

DATE OF FIRST PATIENT'S ENROLMENT

1 December 2003.