The effect of pregnant mare serum gonadotropin on mouse embryos fertilized in vivo or in vitro

Mild stimulation protocol vs conventional controlled ovarian stimulation protocol in poor ovarian response patients: a prospective randomized controlled trial

PURPOSE

To compare the efficacy of mild ovarian stimulation protocol and conventional controlled ovarian stimulation (COS) protocol for poor ovarian response (POR) patients undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI).

METHODS

This single-center prospective randomized controlled trial conducted from September 2013 to September 2015, including 191 patients who met the Bologna criteria of POR. Ninety-seven patients allocated to the mild ovarian stimulation group (MS group) were stimulated according to the letrozole/antagonist protocol, while 94 patients in the controlled ovarian stimulation group (COS group) were stimulated according to a high dose of gonadotropin (Gn) combined with gonadotropin-releasing hormone agonist (GnRH-a) stop protocol. The cumulative live birth rate was the primary outcome. Chinese clinical trial number ChiCTR-TRC-13003454.

RESULTS

Comparing with the COS group, both the stimulation duration and the total gonadotropin dose were significantly shorter and lower in the MS group (P < 0.001). A higher number of retrieved oocytes (P = 0.003) and transferrable embryos (P = 0.029) were obtained in the COS group. The cumulative live birth rates (OR 1.103; 95% CI 0.53 to 2.28; P = 0.791) were comparable between the two groups.

CONCLUSIONS

The increase of Gn dose during ovulation stimulation was associated with a higher number of transferrable embryos for POR patients, but this increase did not lead to a concomitant improvement of reproductive outcome, especially in terms of the cumulative live birth rate. Using a mild stimulation protocol was economically preferential while it was as effective as higher doses of Gn stimulation protocol in reproductive outcome for POR patients.

The effects of low-dose human chorionic gonadotropin combined with human menopausal gonadotropin protocol on women with hypogonadotropic hypogonadism undergoing ovarian stimulation for in vitro fertilization

OBJECTIVES

To investigate the effects of low-dose human chorionic gonadotropin (hCG) combined with human menopausal gonadotropin (HMG) protocol on cycle characteristics and outcomes of infertile women with hypogonadotropic hypogonadism (HH) undergoing ovarian stimulation for in vitro fertilization (IVF).

DESIGN

A retrospective cohort study.

SETTING

Tertiary-care academic medical centre.

PATIENT(S)

Forty-six infertile patients with HH and seventy-one infertile patients with tubal factor (TF) infertility undergoing IVF.

INTERVENTION(S)

In the study group, all 46 HH patients were given low-dose hCG (50-300IU/d) in combination with HMG daily from cycle day 3. Meanwhile, a control group consisting of 71 patients with tubal factor infertility was set up, where the infertile women were given triptorelin 3.75 mg on cycle day 3 for desensitization and started stimulation with HMG only 5 weeks later. Transvaginal ultrasound and serum sex steroids were used for monitoring the development of follicles. Ovulation was triggered by hCG 5000IU when dominant follicles matured. Viable embryos were transferred on the third day after ovum pickup or cryopreserved for later transfer.

MAIN OUTCOME MEASURE(S)

The primary outcome measure was the clinical pregnancy rate. Secondary outcomes included hCG day P4, ratio of E2/follicle count, number of oocytes retrieved, number of viable embryos, implantation rate, ongoing pregnancy rate and cumulative pregnancy rate.

RESULT(S)

With lower basal FSH, LH and E2, HH patients showed longer HMG stimulation duration (13 (10-22) d vs 12 (8-18) d, P < .001) and higher HMG dose (2960 ± 560 IU vs 2663 ± 538 IU, P = .005). Whilst the antral follicle count (AFC), number of follicles with diameters greater than 10mm on trigger day and oocytes retrieved were less in the HH group, the number of follicles with diameters greater than 14 mm and viable embryos were comparable. The ratio of E2/follicle count (>10 mm) and E2/follicle count (>14 mm) were distinctively higher in the HH group (1056 ± 281 vs 830 ± 245, P < .001; 1545 ± 570 vs 1312 ± 594pmol/L, P = .037; respectively). The clinical pregnancy rate, implantation rate, ongoing pregnancy rate and cumulative pregnancy rate per woman were comparable between the two groups. Comparison among the subgroups with different hCG dosage showed that HMG duration shortened with the increase of daily hCG dose (14.84 ± 2.88 vs 13.96 ± 2.63 vs 12.96 ± 1.30 days, P = .037). No significant differences were detected in outcomes between fresh embryo transfer (ET) group and frozen-thawed embryo transfer (FET) group.

CONCLUSION(S)

Low-dose hCG combined with HMG is a feasible protocol for HH women undergoing ovarian stimulation in IVF, providing favourable cycle characteristics and pregnancy rates. Low-dose hCG reduces HMG duration, whilst the hCG dose and embryo quality are not positively correlated. The outcomes of FET are comparable to ET, which provides a greater chance of success from IVF in the low responders with HH.

Activin Decoy Receptor ActRIIB:Fc Lowers FSH and Therapeutically Restores Oocyte Yield, Prevents Oocyte Chromosome Misalignments and Spindle Aberrations, and Increases Fertility in Midlife Female SAMP8 Mice

Women of advanced maternal age (AMA) (age ≥ 35) have increased rates of infertility, miscarriages, and trisomic pregnancies. Collectively these conditions are called "egg infertility." A root cause of egg infertility is increased rates of oocyte aneuploidy with age. AMA women often have elevated endogenous FSH. Female senescence-accelerated mouse-prone-8 (SAMP8) has increased rates of oocyte spindle aberrations, diminished fertility, and rising endogenous FSH with age. We hypothesize that elevated FSH during the oocyte's FSH-responsive growth period is a cause of abnormalities in the meiotic spindle. We report that eggs from SAMP8 mice treated with equine chorionic gonadotropin (eCG) for the period of oocyte growth have increased chromosome and spindle misalignments. Activin is a molecule that raises FSH, and ActRIIB:Fc is an activin decoy receptor that binds and sequesters activin. We report that ActRIIB:Fc treatment of midlife SAMP8 mice for the duration of oocyte growth lowers FSH, prevents egg chromosome and spindle misalignments, and increases litter sizes. AMA patients can also have poor responsiveness to FSH stimulation. We report that although eCG lowers yields of viable oocytes, ActRIIB:Fc increases yields of viable oocytes. ActRIIB:Fc and eCG cotreatment markedly reduces yields of viable oocytes. These data are consistent with the hypothesis that elevated FSH contributes to egg aneuploidy, declining fertility, and poor ovarian response and that ActRIIB:Fc can prevent egg aneuploidy, increase fertility, and improve ovarian response. Future studies will continue to examine whether ActRIIB:Fc works via FSH and/or other pathways and whether ActRIIB:Fc can prevent aneuploidy, increase fertility, and improve stimulation responsiveness in AMA women.

The determination of possible genetic damage to women undergoing in vitro fertilization due to infertility caused by the male factor

In this study, we aimed at determining possible genetic damage to women who were exposed to in vitro fertilization (IVF) due to infertility with male factor. Four different genotoxicity tests were used in human lymphocytes in this study with regard to chromosomal aberration (CA), sister chromatid exchange (SCE), micronucleus (MN), and comet tests. There was a statistically significant increase in sister chromatid exchange (SCE) test in the study group compared with the control group. In addition, a higher rate of MN frequency was determined only in the 21–30 age range study group compared with the control group in the same age range. On the other hand, MN frequency did not differ significantly between the control and total study groups. In addition, there was no significant difference between the control group and the study group in terms of mitotic (MI), replication (RI), and nuclear division (NDI) indices. Furthermore, there was no statistically significant increase for chromosomal aberration and DNA damage to the study groups. Our results showed that in vitro fertilization treatments have a weak risk at the genetic level in cultured human lymphocytes.

Assisted reproductive technique outcomes in hypogonadotropic hypogonadism women

BACKGROUND AND OBJECTIVES

To evaluate the outcomes of using in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI cycle) techniques in hypogonadotropic hypogonadism (HH) women and comparing them to women with tubal factor infertility.

DESIGN AND SETTINGS

Retrospective cohort study in Royan Institute, Iran.

PATIENTS AND METHODS

Data from 81 HH patients treated with IVF/ICSI in the period from early 2009 until the end of 2010 were analyzed and compared with treatment results from 89 patients with tubal factor infertility. Moreover, data from the HH patients were analyzed with respect to the age factor. P value < .05 was considered statistically significant. The main outcome measures were implantation, fertilization, pregnancy, and live birth rates.

RESULTS

Despite a higher fertilization rate and higher number of grade A/B embryos transferred in the tubal factor group, the implantation, pregnancy, and live birth rates were found to be similar between the 2 groups (P=.3, P=.1, P=.1, respectively). When the HH patients were evaluated according to the age factor, no significant difference was found regarding outcome parameters (P=.2).

CONCLUSIONS

HH women that were treated with IVF/ICSI cycles seem to have a sound potential for pregnancy, even in advanced age patients.

Patient selection criteria for blastocyst transfers in extended embryo culture programs

PURPOSE

To identify the correlation between different cycles, patient factors and blastocyst characteristics.

METHODS

The study included 420 patients undergoing ICSI cycles and 2781 graded blastocysts, which took into account the blastocyst quality. The correlations between the blastocyst parameters and the patient and cycle characteristics were assessed.

RESULTS

The blastocyst development was negatively correlated with the maternal age, BMI and dose of FSH. The ICM was negatively correlated with the FSH dose, whereas the TE quality was influenced by the FSH dose, the maternal age and the number of retrieved oocytes. The embryo morphology on days two and three may predict the blastocyst developmental competence.

CONCLUSIONS

Older patients and patients with high BMI should not be included in extended embryo culture programmes. The extended culture may not favour embryos with poor morphology on days two and three of development. Additionally, a lower ovarian stimulation and decreased oocyte yields may lead to the development of high-quality blastocysts.

Contributing factors for the incidence of aneuploidy in older patients undergoing intracytoplasmic sperm injection cycles

PURPOSE

To evaluate different factors that might affect the incidence of embryo aneuploidy in intracytoplasmic sperm injection cycles (ICSI).

METHODS

One hundred and ninety ICSI cycles in conjunction with preimplantation genetic screening (PGS) were included. The influence of the following variables on the aneuploidy incidence was evaluated: (i) maternal and (ii) paternal ages, (iii) dose of FSH administered, (iv) dose of FSH per number of retrieved matured oocytes (FSH/MII), (v) serum 17β-oestradiol levels on the ovulation trigger day, (vi) aspirated follicles and (vii) retrieved oocytes.

RESULTS

A total of 440 embryos were successfully biopsied, of which 240 were considered euploid and 200 were considered aneuploid. The paternal age (Slope: 0.2, p = 0.372), total dose of FSH (Slope: 0.2, p = 0.218), FSH/MII (Slope: 0.1, p = 0.296) and 17β-oestradiol levels (Slope: 0.2, p = 0.378) were not correlated with the presence of aneuploidy. However, the maternal age (Slope: 1.7, p < 0.01), aspirated follicles (Slope: 1.9, p < 0.01) and retrieved oocytes (Slope: 2.6, p < 0.01) were negatively correlated with the incidence of aneuploidy.

CONCLUSIONS

Even in older patients, lower oocyte yields may represent a more appropriate response to ovarian stimulation, allowing the most competent follicles and oocytes to develop and thereby reducing the occurrence of embryo aneuploidy.

Early and delayed aspects of nuclear reprogramming during cloning

The successful production of viable progeny following adult somatic cell nuclear transfer (cloning) provides exciting new opportunities for basic research for investigating early embryogenesis, for the propagation of valuable or endangered animals, for the production of genetically engineered animals, and possibly for developing therapeutically valuable stem cells. Successful cloning requires efficient reprogramming of gene expression to silence donor cell gene expression and activate an embryonic pattern of gene expression. Recent observations indicate that reprogramming may be initiated by early events that occur soon after nuclear transfer, but then continues as development progresses through cleavage and probably to gastrulation. Because reprogramming is slow and progressive, cloned embryos have dramatically altered characteristics in comparison with fertilized embryos. Events that occur early following nuclear transfer may be essential prerequisites for the later events. Additionally, the later reprogramming events may be inhibited by sub-optimum culture environments that exist because of the altered characteristics of cloned embryos. By addressing the unique requirements of cloned embryos, the entire process of reprogramming may be accelerated, thus increasing cloning efficiency.

Aurora kinase-A regulates microtubule organizing center (MTOC) localization, chromosome dynamics, and histone-H3 phosphorylation in mouse oocytes

Aurora kinases (AURKs) are conserved serine/threonine kinases, crucial in regulating cell cycle events. Mammalian oocytes express all three Aurk isoforms throughout meiosis, with AurkA being the predominant isoform. Inhibition of all AURK isoforms by pharmacological means disrupts oocyte meiosis. Therefore, AurkA short interfering RNA (siRNA) was performed to silence AurkA gene expression in mouse oocytes and to further assess the function of AurkA during meiosis by analyzing subsequent loss-of-function oocyte phenotypes. Results indicated that AurkA siRNA applied in our experiments specifically knocked down both AurkA gene and protein expression without influencing transcript levels of AurkB/AurkC and other endogenous protein expression, such as GAPDH and ERK-2. AURKA was not essential for resumption of meiosis, but it potentiated oocyte meiotic progression. Knockdown of AurkA led to a significant reduction in the number of oocytes proceeding to metaphase II (MII). AurkA siRNA resulted in abnormal spindle assembly, improper localization of microtubule organizing centers (MTOCs) and misalignment of chromosomes in metaphase I (MI) oocytes. Co-immunoprecipitations demonstrated that AURKA was physically associated with phospho-Histone H3 ser10 in meiotic oocytes. AurkA siRNA dramatically reduced Histone H3 ser10 phosphorylation, but not ser28, and resulted in a significant increase of abnormal chromosome segregation in MII oocytes. In conclusion, as a predominant isoform among Aurks in oocytes, AurkA plays critical roles in mouse oocyte meiosis by regulating spindle and chromosome dynamics.

Ovarian stimulation and the risk of aneuploid conceptions

OBJECTIVE

To examine the rate of aneuploidy in missed abortions in patients who conceived after FSH ovarian stimulation compared with women who conceived in a natural cycle.

DESIGN

Retrospective cohort.

SETTING

Academic reproductive endocrinology and infertility center.

PATIENT(S)

Women with karyotyping of products of conception (POC) from a missed abortion from January 1999 through August 2007. The rate of aneuploidy was compared between patients with a history of infertility who conceived naturally and patients with a history of infertility who conceived with FSH treatment.

INTERVENTION(S)

Ovarian stimulation with FSH, intrauterine insemination, and in vitro fertilization; genetic testing of POC after dilation and curettage.

MAIN OUTCOME MEASURE(S)

Embryonic karyotype.

RESULT(S)

A total of 229 pregnancies met inclusion criteria, and of these, 64% had an abnormal karyotype. The rate of aneuploidy was 63% in the study group and 70% in the control group. This difference was not statistically significant.

CONCLUSION(S)

The incidence of embryonic aneuploidy was not higher in pregnancies conceived with FSH stimulation compared with spontaneous conceptions in infertility patients. This suggests that exogenous FSH exposure does not increase the risk of aneuploidy.

High follicle-stimulating hormone increases aneuploidy in human oocytes matured in vitro

OBJECTIVE

To study the effect of FSH on the aneuploidy risk of human oocytes matured in vitro.

DESIGN

Prospective study.

SETTING

Hospital-based IVF center.

PATIENT(S)

Patients with male factor infertility undergoing intracytoplasmic sperm injection (ICSI) cycles.

INTERVENTION(S)

Immature oocytes were put into five groups according to the FSH concentration (0, 5.5, 22, 100, and 2,000 ng/mL) in in vitro maturation (IVM) medium. Spindles were observed under a polarized microscope before polar body biopsy. Fixed polar bodies and corresponding oocytes were examined on chromosomes 13, 16, 18, 21, and 22 by fluorescence in situ hybridization. Oocytes matured in 5.5 and 2,000 ng/mL FSH were immunostained for tubulin and chromatin.

MAIN OUTCOME MEASURE(S)

Aneuploidy rate, spindle visualization rate, and spindle morphology.

RESULT(S)

The frequency rates of aneuploidy were 26.7%, 23.3%, 36.75%, 46.67%, and 63.3% in the five FSH groups, respectively. There was a significantly higher aneuploidy rate in oocytes matured in the 2,000 ng/mL FSH group. The spindle visualization rates assessed under PolScope were not significantly different between aneuploid and normal oocytes. There was no difference in spindle morphology between the 2,000 and 5.5 ng/mL FSH groups.

CONCLUSION(S)

High-concentration FSH in IVM medium significantly increased the first meiotic division error, resulting in more aneuploid oocytes during IVM.

The effect of progesterone and exogenous gonadotropin on preimplantation mouse embryo development and implantation

The aim of this study was to evaluate the effects of progesterone and ovarian stimulation on the development and implantation rate of mouse embryos. Two-cell embryos were collected from superovulated mice and cultured in the presence of different concentrations of progesterone (0, 5, 10 and 20 ng/ml). Also other mice were rendered pregnant in unstimulated, unstimulated progesterone-injected, superovulated and superovulated progesterone-injected groups to collect the blastocysts. The number of blastocysts and implantation sites were recorded on the 4th and 7th day of pregnancy, respectively. The diameter and cell number of blastocysts were analyzed in the in vitro and in vivo groups. After 120 h culture, the percentage of hatched blastocyst embryos in control and 5, 10 and 20 ng/ml progesterone-injected groups were 63.9%, 64.2%, 64.2% and 75.6% respectively. There were significant differences between the developmental rates of embryos in the presence of 20 ng/ml progesterone and the control and other concentrations of progesterone-injected groups (P< or =0.001). The in vivo blastocyst survival rate (97.68%) and implantation rate (92.06%) in the unstimulated and progesterone-injected groups were higher than in the other groups. Blastocyst cell numbers in the superovulated (128.62 +/- 1.30) and superovulated progesterone-injected groups (126.88 +/- 1.60) were significantly different from the control (P<0.001). The progesterone injection without ovarian induction improved the embryo survival and implantation rates, but after superovulation it did not ameliorate the negative effects of superovulation on the implantation rate.

Molecular mechanisms of ovulation: co-ordination through the cumulus complex

Successful ovulation requires that developmentally competent oocytes are released with appropriate timing from the ovarian follicle. Somatic cells of the follicle sense the ovulatory stimulus and guide resumption of meiosis and release of the oocyte, as well as structural remodelling and luteinization of the follicle. Complex intercellular communication co-ordinates critical stages of oocyte maturation and links this process with release from the follicle. To achieve these outcomes, ovulation is controlled through multiple inputs, including endocrine hormones, immune and metabolic signals, as well as intrafollicular paracrine factors from the theca, mural and cumulus granulosa cells and the oocyte itself. This review focuses on the recent advances in understanding of molecular mechanisms that commence after the gonadotrophin surge and culminate with release of the oocyte. These mechanisms include intracellular signalling, gene regulation and remodelling of tissue structure in each of the distinct ovarian compartments. Most critical ovulatory mediators exert effects through the cumulus cell complex that surrounds and connects with the oocyte. The convergence of ovulatory signals through the cumulus complex co-ordinates the key mechanistic processes that mediate and control oocyte maturation and ovulation.

What is the underlying cause of aneuploidy associated with increasing maternal age? Is it associated with elevated levels of gonadotropins?

Aneuploidy is the most common chromosomal abnormality and also is the leading cause of early fetal loss and serious mental retardations. Except for the advanced maternal age, there is no clearly established factor for the development of aneuploidy. On the other hand, advanced maternal age is well characterized with elevated gonadotropin levels due to the decreased ovarian reserve. Such high level gonadotropins are also seen physiologically in the adolescent period. Both age groups may have an increased risk for having a baby with chromosomal abnormality. On the other hand, high doses of gonadotropins are widely used in artificial reproductive technologies (ART). Low pregnancy and high abortion rates in ART practices may be explained by higher incidence of chromosomal abnormalities in the unfertilized oocytes maturated by high dose gonadotropins. Gonadotropins are also found to induce congenital malformations and chromosomal abnormalities in some animal studies. From this point of view, we hypothesized that gonadotropins might have a role in the development of aneuploidy. If this hypothesis is true, basal serum FSH levels may be used as a screening test in preconceptional period for assessment of the aneuploidy risk in low risk population. Furthermore, new ART protocols using low dose gonadotropins should be developed in order to improve pregnancy outcomes and possibly to prevent aneuploidy.

Maternal Factors Controlling Blastomere Fragmentation in Early Mouse Embryos1

Interactions between sperm and egg are required to maintain embryo viability and cellular integrity. Differential transcriptional activities and epigenetic differences that include genomic imprinting provide mechanisms by which complementary parental genome functions support early embryogenesis. We previously showed that cytofragmentation can be influenced by the specific combination of maternal and paternal genotypes. Using maternal pronuclear transfer in mouse embryos, we examined the cellular basis for the maternal genotype effect. We found that the maternal genotype effect is predominantly controlled by the maternal pronucleus, with a lesser role played by the ooplasm. This effect of the maternal pronucleus is sensitive to alpha-amanitin treatment. The effect of the maternal component of the embryonic genome on cytofragmentation constitutes the earliest known effect of the embryonic genome on mammalian embryo phenotype. The results also indicate that clinical procedures seeking to define or manipulate oocyte quality in humans should take into account early effects of the embryonic genome, particularly the maternal genome.

Acceleration of embryo transport in superovulated adult rats

The etiology of reduced fertility in rodents and humans after exogenous gonadotropin-induced superovulation is unknown. This study examines implantation failure in adult rats induced to superovulate by gonadotropin treatment. After multiple injections of pregnant mare serum gonadotropin (PMSG) followed by human chorionic gonadotropin (hCG), superovulation in adult rats was confirmed on day-1 of pregnancy, however, on day-13, no implantation sites were observed. Daily flushing of oviducts and uteri revealed that the number of embryos recovered from superovulated rats on day-2 was only one-third of that retrieved on day-1. The numbers of embryos retrieved on these days from the oviducts of control rats, however, were almost equivalent. On day-3, no embryos were retrieved from either the oviducts or uteri of superovulated rats, while all embryos from control rats were found in the oviducts. Most embryos recovered from superovulated rats showed normal development. Compared to levels in control rats, serum estradiol (E2) in superovulated rats increased significantly on days-2 and -3 of pregnancy, whereas, serum progesterone (P) levels remained unchanged. Thus, E2/P ratio increased on days-2 and -3 of pregnancy in superovulated adult rats coinciding with the timing of embryo transport acceleration. Our results suggest that superovulated oocytes can be fertilized and reach an early stage of development within the oviduct. Implantation failure in superovulated rats may be due to the accelerated embryo transport resulting from elevated E2/P ratio.

Cytogenetic analysis of Day-4 embryos from PMSG/hCG-treated prepuberal gilts

Prepuberal gilts were treated with pregnant mare serum gonadotropin (PMSG) to study the effects of its dosage on ovulation rate, fertilization rate after artificial insemination, embryo viability, and rate of development and incidence of chromosome abnormalities in Day-4 embryos. Gilts received 750 IU, 1250 IU or 1500 IU of PMSG, followed 72 h later by 500 IU human chorionic gonadotropin (hCG). Gilts were inseminated 28 to 30 h following the hCG injection, and resulting embryos were collected on Day 4 post ovulation. Ovulation rate was higher in the 1250 IU group than in the 1500 IU group or the 750 IU group. The 1500 IU dose caused excessive stimulation of the ovary, resulting in the occurrence of large (>10mm diameter) unovulated follicles, reduced fertilization rate and low embryo recovery rate. There was no difference in the incidence of chromosome abnormalities among the three groups, although the 1500 IU group had higher embryonic mortality than the two lower dose groups. A dose of 1250 IU PMSG increased ovulation rate above that achieved by 750 IU and, therefore, increased the number of oocytes or embryos available for transfer or for other studies, without sacrificing embryo viability or increasing the incidence of chromosome abnormalities.

Pregnant mares' serum gonadotropin source influences fertilization and fresh or thawed embryo development, but the effect is genotype specific

The influence of the source of pregnant mares' serum gonadotropin (PMSG) on the number, quality, and in vitro development of mouse embryos before and after freezing was evaluated among three genotypes: N:NIH(S), C57BL/6N, and C3H/HeN-MTV-Immature females were given PMSG from one of five commercial sources. Following collection (116 hr later), embryos were evaluated for stage of development, and four- to eight-cell embryos were pooled within genotype and assigned to standardized fresh or freeze-thaw culture trials. Different PMSG sources stimulated the production of different numbers of total embryos (P less than 0.05) but not necessarily more embryos suitable for freezing. Differences in embryo production among genotypes indicated that absolute embryo numbers using a single mouse genotype may not accurately reflect the potency of a specific gonadotropin source. The PMSG source also affected the ability of an embryo to survive in culture either immediately after collection or after frozen storage. The effect, however, was genotype specific, with some mouse strains being relatively insensitive to PMSG source, whereas gonadotropin source played a major role in determining in vitro viability in others. Development rates for freshly collected embryos differed, often inconsistently, from those of thawed embryos regardless of the PMSG source used, demonstrating that fresh embryo development cannot be used to estimate expected post-thaw survival. In vitro development of thawed embryos is influenced not only by genotype, but also the source of the gonadotropin used to promote follicular development and oocyte maturation. These findings may explain, in part, the wide variation in embryo viability and culture rates reported among laboratories and intraspecies animal populations.

Factors affecting fetal loss in induction of ovulation with gonadotropins: increased abortion rates related to hormonal profiles in conceptual cycles

Thirty-six first-trimester abortions (9.7%), 16 second-trimester abortions (4.3%), 11 ectopic pregnancies (2.9%), and 10 stillbirths (2.7%) occurred in 373 conceptual cycles after gonadotropin induction of ovulation. Fetal wastage was higher in spontaneous pregnancies that occurred before therapy (54.3%, p less than 0.0001) and lower with subsequent spontaneous pregnancies (10.1%, p less than 0.05). Significant risk factors for overall fetal loss during induced ovulation were a continuous rise of estrogen excretion until ovulation (p less than 0.01) and previous abortion (p less than 0.05). For first-trimester abortion, the risk factor was continuous estrogen rise (p less than 0.01); for second-trimester abortion, the risk factors were a low luteal pregnanediol-to-estrogen excretion ratio (p less than 0.002), increased age at conception (p less than 0.02), and high baseline estrogen excretion (p less than 0.05). Multiple pregnancy was not significant. The continuous rising estrogen pattern may serve as a marker of abnormal oocyte maturation. We propose that future studies on infertility treatment should report on pregnancy outcome.

Anti-oestrogens: their clinical physiology and use in reproductive medicine

The anti-oestrogens are important both as therapeutic agents in reproductive medicine and as tools to investigate the physiology of the oestrogen receptor and hormonal control mechanisms. Clomiphene occupies the oestradiol receptor and, although initially stimulatory, has a net antagonistic effect as oestrogen receptors are not replenished. The major fertility-enhancing effect is to cause an increase in LH and FSH output by increasing the frequency of pulsatile output of these hormones. Many effects due to an anti-oestrogenic effect have been postulated; some, such as an adverse effect on cervical mucus, have been proven. The clinical use of the anti-oestrogens is outlined in Table 1. In well chosen patients a rewarding pregnancy rate is obtained with minimal intervention and few important side-effects. The challenge for the reproductive biologist is successfully to manage the patient who is clomiphene-resistant, either because of failure to ovulate or failure to conceive once ovulation is induced.

Effects of high-dose and multiple-dose gonadotropin stimulation on mouse oocyte quality as assessed by preimplantation development following in vitro fertilization

The effects of increasing the level of ovarian stimulation on preimplantation embryonic development were assessed using a mouse in vitro fertilization system. When F1 hybrid (C57BL/6 X CBA/Ca) mice received a single injection of 5 IU pregnant mare's serum gonadotropin (PMSG) followed 60 hr later by 5 IU human chorionic gonadotropin (hCG) approximately 50% of the resultant postovulatory oocytes developed to the blastocyst stage following in vitro fertilization. Increasing the single dose of PMSG to 10 or 15 IU resulted in significant reductions in the frequency of development to the blastocyst stage. When one or two additional doses of 5 IU PMSG were administered 24 and 48 hr after an initial injection of 5 IU, lower frequencies of oocytes with the potential for full preimplantation development were again observed. This reduction in gamete quality was significantly greater when the final dose of PMSG was administered only 12 hr prior to hCG. The results suggest that excessive gonadotropin stimulation may compromise the quality of the preimplantation embryos obtained following in vitro fertilization and that the timing of gonadotropin administration may also be critical.