Maternal age effect: the enigma of Down syndrome and other trisomic conditions

Small area estimation of sparse disease counts using shared component models-application to birth defect registry data in New South Wales, Australia

In the field of disease mapping, little has been done to address the issue of analysing sparse health datasets. We hypothesised that by modelling two outcomes simultaneously, one would be able to better estimate the outcome with a sparse count. We tested this hypothesis utilising Bayesian models, studying both birth defects and caesarean sections using data from two large, linked birth registries in New South Wales from 1990 to 2004. We compared four spatial models across seven birth defects: spina bifida, ventricular septal defect, OS atrial septal defect, patent ductus arteriosus, cleft lip and or palate, trisomy 21 and hypospadias. For three of the birth defects, the shared component model with a zero-inflated Poisson (ZIP) extension performed better than other simpler models, having a lower deviance information criteria (DIC). With spina bifida, the ratio of relative risk associated with the shared component was 2.82 (95% CI: 1.46-5.67). We found that shared component models are potentially beneficial, but only if there is a reasonably strong spatial correlation in effect for the study and referent outcomes.

Miscarriage risk for IVF pregnancies in poor responders to ovarian hyperstimulation

The increasing miscarriage rate with advancing female age is attributed to a decline in oocyte quality. A poor response to ovarian hyperstimulation is often an expression of a decrease in oocyte quantity. Although oocyte quality and quantity both decrease as a result of ovarian ageing, it is unclear whether these two processes are related to each other. To investigate the relationship between oocyte quantity and quality, we compared miscarriage rates between IVF treated women with a poor and normal response, respectively. Data were studied from a retrospective nationwide cohort of Dutch women undergoing IVF treatment from 1983 to 1995. Women achieving an ongoing pregnancy after their first complete IVF cycle (n=1468) were compared with those experiencing miscarriage (n=357) with respect to their ovarian response. Logistic regression analysis showed a statistically significant association between poor response (fewer than four retrieved oocytes) and miscarriage (P=0.001). Due to interaction, this association became stronger with increasing female age. Among women < 36 years, miscarriage rates between poor and normal responders did not differ, whereas among women 36 years poor responders had a statistically significant increased miscarriage rate compared with normal responders (P=0.001). These results support the hypothesis of a relationship between quantitative ovarian reserve and oocyte quality.

Ovarian aging: mechanisms and clinical consequences

Menopause is the final step in the process referred to as ovarian ageing. The age related decrease in follicle numbers dictates the onset of cycle irregularity and the final cessation of menses. The parallel decay in oocyte quality contributes to the gradual decline in fertility and the final occurrence of natural sterility. Endocrine changes mainly relate to the decline in the negative feedback from ovarian factors at the hypothalamo-pituitary unit. The declining cohort of antral follicles with age first results in gradually elevated FSH levels, followed by subsequent stages of overt cycle irregularity. The gradual decline in the size of the antral follicle cohort is best represented by decreasing levels of anti-Mullerian hormone. The variability of ovarian ageing among women is evident from the large variation in age at menopause. The identification of women who have severely decreased ovarian reserve for their age is clinically relevant. Ovarian reserve tests have appeared to be fairly accurate in predicting response to ovarian stimulation in the assisted reproductive technology (ART) setting. The capacity to predict the chances for spontaneous pregnancy or pregnancy after ART appears very limited. As menopause and the preceding decline in oocyte quality seem to have a fixed time interval, tests that predict the age at menopause may be useful to assess individual reproductive lifespan. Especially genetic studies, both addressing candidate gene and genome wide association, have identified several interesting loci of small genetic variation that may determine fetal follicle pool development and subsequent wastage of his pool over time. Improved knowledge of the ovarian ageing mechanisms may ultimately provide tools for prediction of menopause and manipulation of the early steps of folliculogenesis for the purpose of contraception and fertility lifespan extension.

Testing ovarian reserve to predict age at menopause

In modern society with women delaying pregnancy, predicting the age of the natural menopause with its preceding infertility will allow making informed choices about when to try starting to have children. Also if premature menopause could be predicted in young women, strategies could be instigated to reduce the long term health risks of early estrogen deficiency. This review examines the physiology of ovarian ageing, with the menopause being the final outcome. Long and short term predictive markers of the age of the menopause and the preceding natural infertility are evaluated. Many subtle changes in the endocrine regulation of ovarian function with advancing age may seem interesting but currently are not clinically useful as a predictive test. Examples are changes in concentrations of estradiol, progesterone, luteinizing hormone (LH) and activin, as well as follicle dynamics. Other features hold more promise. Among these are chronological age, family history, anti-Müllerian hormone (AMH), poor response to in vitro fertilization (IVF), basal follicle-stimulating hormone (FSH) and the antral follicle count for long term prediction. For short term prediction, cycle shortening and occurrence of vasomotor symptoms may prove useful. To date, none of these markers has been found to have sufficient predictive accuracy in individual women. Results of new and ongoing longitudinal studies may provide better predictive models. In particular, use of genetic profiles may add to the accuracy of currently known markers.

Aging of the human ovary and testis

Aging is associated with structural and functional alterations in all organs of the human body. The aging of gonads represents in this respect a special case, because these organs are not functional for the whole lifespan of an individual and their normal function is not indispensable for functions of the rest of the body. Ovarian function lasts for the reproductive life of a woman, i.e., from menarche until menopause. The testicular endocrine function, in contrast, begins already in utero, is interrupted between neonatal life and puberty, and continues thereafter along with spermatogenesis, with only slight decline, until old age. The aging processes of the ovary and testis are therefore very different. We describe in this review the structural and functional alterations in the human ovary and testis upon aging. Special emphasis will be given to clinically significant alterations, which in women concern the causes and consequences of the individual variability of fertility during the latter part of the reproductive age. The clinically important aspect of testicular aging entails the decline of androgen production in aging men.

Effects of ooplasm manipulation on DNA methylation and growth of progeny in mice

New techniques to boost male and female fertility are being pioneered at a rapid pace in fertility clinics to increase the efficiency of assisted reproduction methods in couples in which natural conception has not been achieved. This study investigates the possible epigenetic effects of ooplasm manipulation methods on postnatal growth and development using a mouse genetic model, with particular emphasis on the possible effects of intergenotype manipulations. We performed interstrain and control intrastrain maternal pronuclear transfers, metaphase-II spindle transfers, and ooplasm transfer between C57BL/6 and DBA/2 mice, and found no major, long-term growth defects or epigenetic abnormalities, in either males or females, associated with intergenotype transfers. Ooplasm transfer itself was associated with reduced viability, and additional subtle effects of ooplasm strain of origin were observed. Both inter- and intrastrain ooplasm transfer were associated with subtle, transient effects on growth early in life. We also performed inter- and intrastrain germinal vesicle transfers (GVTs). Interstrain GVT females, but not males, had significantly lower body weights at birth and thereafter compared with the intrastrain GVT and non-GVT controls. No GVT-associated changes were observed in DNA methylation of the Mup1, Rasgrf1, H19, Snrpn, or Peg3 genes, nor any difference in expression of the imprinted Rasgrf1, Igf2r, or Mest genes. These results indicate that some ooplasm manipulation procedures may exert subtle effects on growth early in life, while intergenotype GVT can result in significant growth deficiencies after birth.

Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down Syndrome Projects

We examined the association between maternal age and chromosome 21 nondisjunction by origin of the meiotic error. We analyzed data from two population-based, case-control studies: Atlanta Down Syndrome Project (1989-1999) and National Down Syndrome Project (2001-2004). Cases were live born infants with trisomy 21 and controls were infants without trisomy 21 delivered in the same geographical regions. We enrolled 1,215 of 1,881 eligible case families and 1,375 of 2,293 controls. We report four primary findings. First, the significant association between advanced maternal age and chromosome 21 nondisjunction was restricted to meiotic errors in the egg; the association was not observed in sperm or in post-zygotic mitotic errors. Second, advanced maternal age was significantly associated with both meiosis I (MI) and meiosis II (MII). For example, compared to mothers of controls, mothers of infants with trisomy 21 due to MI nondisjunction were 8.5 times more likely to be >or=40 years old than 20-24 years old at the birth of the index case (95% CI=5.6-12.9). Where nondisjunction occurred in MII, mothers were 15.1 times more likely to be >or=40 years (95% CI = 8.4-27.3). Third, the ratio of MI to MII errors differed by maternal age. The ratio was lower among women <19 years of age and those >or=40 years (2.1, 2.3, respectively) and higher in the middle age group (3.6). Lastly, we found no effect of grand-maternal age on the risk for maternal nondisjunction. This study emphasizes the complex association between advanced maternal age and nondisjunction of chromosome 21 during oogenesis.

Oocyte Mitochondria: Strategies to Improve Embrbryogenesis

Mitochondria play a central role to provide ATP for fertilization and preimplantation embryo development in the ooplasm. The mitochondrial dysfunction of oocyte has been proposed as one of the causes of high levels of developmental retardation and arrest that occur in preimplantation embryos generated using Assisted Reproductive Technology. Cytoplasmic transfer (CT) from a donor to a recipient oocyte has been applied to infertility due to dysfunctional ooplasm, with resulting pregnancies and births. However, neither the efficacy nor safety of this procedure has been appropriately investigated. In order to improve embryogenesis, we observed the mitochondrial distribution in ooplasma under the several conditions using mitochondrial GFP-transgenic mice (mtGFP-tg mice) in which the mitochondria are visualized by GFP. In this report, we will present our research about the mitochondrial distribution in ooplasm during early embryogenesis and the fate of injected donor mitochondria after CT using mtGFP-tg mice. The mitochondria in ooplasm from the germinal vesicle stage to the morula stage were accumulated in the perinuclear region. The mitochondria of the mtGFP-tg mouse oocyte transferred into the wild type mouse embryo could be observed until the blastocysts stage, suggesting that the mtGFP-tg mice oocyte is very useful for visual observation of the mitochondrial distribution in the oocyte, and that the aberrant early developmental competences due to the oocyte mitochondrial dysfunction may be overcome by transferring the "normal" mitochondria.

Follicular fluid VEGF levels directly correlate with perifollicular blood flow in normoresponder patients undergoing IVF

BACKGROUND

It has become increasingly clear that the follicular microenvironment of the maturing human oocyte is a determining factor for the implantation potential of an embryo deriving from that oocyte. Indeed the quality and maturity of an oocyte are influenced by the level of intrafollicular oxygen content which, in turn, is proportional to the degree of follicular vascularity. The aim of the study was to establish whether there is a relationship between follicular fluid VEGF concentrations, perifollicular vascularity and reproductive outcome in normal responders under the age of 35 undergoing IVF.

MATERIALS AND METHODS

Sixty-one consecutive patients, all at their first IVF cycle, were included in the study. All patients had primary infertility due to male factor or tubal factor. At oocyte retrieval, the perifollicular vascularity of two follicles per ovary was estimated qualitatively through power Doppler blood flow, for a total of two hundred forty-four follicles. The follicular fluid from the identified follicles was centrifuged and stored until VEGF assay. The maturity and fertilization rate of the corresponding oocytes as well as embryo quality and pregnancy rate were recorded.

RESULTS

In our study, we found VEGF levels to be significantly correlated with grade of perifollicular vascularity. Oocytes obtained from follicles with the higher grade of vascularization also showed a higher rate of fertilization, embryos, a better quality and higher pregnancy rates were obtained in women with highly vascularized follicles. Perifollicular blood flow doppler indices seem to predict oocyte viability and quality. Moreover, VEGF may play a potential role in the development of the perifollicular capillary network.

DISCUSSION

The ability of a given follicle to express VEGF and develop an adequate vascular network may be inter-related in patients under the age of 35. An adequate blood supply may be fundamental important in the regulation of intrafollicular oxygen levels and the determination of oocyte quality.

Oxidative stress impairs oocyte quality and melatonin protects oocytes from free radical damage and improves fertilization rate

We investigated the relationship between oxidative stress and poor oocyte quality and whether the antioxidant melatonin improves oocyte quality. Follicular fluid was sampled at oocyte retrieval during in vitro fertilization and embryo transfer (IVF-ET). Intrafollicular concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in women with high rates of degenerate oocytes were significantly higher than those with low rates of degenerate oocytes. As there was a negative correlation between intrafollicular concentrations of 8-OHdG and melatonin, 18 patients undergoing IVF-ET were given melatonin (3 mg/day), vitamin E (600 mg/day) or both melatonin and vitamin E. Intrafollicular concentrations of 8-OHdG and hexanoyl-lysine adduct were significantly reduced by these antioxidant treatments. One hundred and fifteen patients who failed to become pregnant with a low fertilization rate (< or =50%) in the previous IVF-ET cycle were divided into two groups during the next IVF-ET procedure; 56 patients with melatonin treatment (3 mg/day) and 59 patients without melatonin treatment. The fertilization rate was improved by melatonin treatment compared to the previous IVF-ET cycle. However, the fertilization rate was not significantly changed without melatonin treatment. Oocytes recovered from preovulatory follicles in mice were incubated with H2O2 for 12 hr. The percentage of mature oocytes with a first polar body was significantly reduced by addition of H2O2 (300 microm). The inhibitory effect of H2O2 was significantly blocked by simultaneous addition of melatonin. In conclusion, oxidative stress causes toxic effects on oocyte maturation and melatonin protects oocytes from oxidative stress. Melatonin is likely to improve oocyte quality and fertilization rates.

Cellular and molecular aspects of ovarian follicle ageing

It is well established that age-related decline of the biological capacity of a woman to reproduce is primarily related to the poor developmental potential of her gametes. This renders female ageing the most significant determinant of success in IVF. Starting with a reference picture of the main molecular and cellular failures of aged oocytes, granulosa cells and follicular microenvironment, this review focuses on age-related biochemical mechanisms underlying these changes. According to the most relevant concept of ageing, age-associated malfuction results from physiological accumulation of irreparable damage to biomolecules as an unavoidable side effect of normal metabolism. More than a decade after the free radical theory of ovarian ageing, biological and clinical research supporting the involvement of oxidative injuries in follicle ageing is discussed. Looking for the aetiology of oxidative stress, we consider the effect of ageing on ovarian and follicular vascularization. Then, we propose a potential role of advanced glycation end-products known to be involved in the physiological ageing of most tissues and organs. We conclude that future investigation of age-related molecular damage in the different ovarian components will be imperative in order to evaluate the possibility to save or rescue the developmental potential of aged oocytes.

Sodium nitroprusside treatment during the superovulation process improves ovarian response and ovarian expression of vascular endothelial growth factor in aged female mice

OBJECTIVE

To investigate whether sodium nitroprusside (SNP) treatment during the superovulation process improves ovarian response and oocyte developmental competence in aged female mice.

DESIGN

Controlled experimental study.

SETTING

Large urban medical center.

ANIMAL(S)

C57BL inbred female mice of three age groups: 6 to 9, 14 to 16, and 25 to 27 weeks.

INTERVENTION(S)

Female mice were co-injected intraperitoneally with SNP (1 muM or 10 muM) and pregnant mare's serum gonadotropin (PMSG), followed by human chorionic gonadotropin injection 48 hours later and then mated with individual males. After 18 hours, zygotes were flushed and the ovaries were isolated. The control group was injected with PMSG.

MAIN OUTCOME MEASURE(S)

The number of zygotes flushed, embryo development to blastocyst stage, and vascular endothelial growth factor (VEGF) expression in ovary.

RESULT(S)

Treatment with SNP statistically significantly increased the number of flushed zygotes and blastocyst formation rate in mice aged 25 to 27 weeks, not but in mice aged less than 16 weeks compared with the control group. The SNP treatment in aged mice increased VEGF expression of the ovary in a dose-dependent manner.

CONCLUSION(S)

These results demonstrate that SNP treatment during the superovulation process improves ovarian response and oocyte developmental competence in aged female. The positive effect of SNP may be associated with increased VEGF expression.

Defective cohesin is associated with age-dependent misaligned chromosomes in oocytes

Aneuploidy often results from chromosome misalignment at metaphases. Oocytes from senescence-accelerated mice (SAM) exhibit increased chromosome misalignment with age, which originates from nuclear factors. This work sought to further characterize the underlying defects of chromosome misalignments. Using immunofluorescence microscopy with specific antibodies, several specific components associated with spindles or chromosomes, including centrosomes, centromeres and cohesin complex were examined. No obvious differences were found in the distribution of centrosome focus at the spindle pole of oocytes from young and aged SAM, regardless of chromosome alignments, although cytoplasmic centrosome foci were significantly reduced in aged SAM (P < 0.0001). Oocytes from both young and aged SAM exhibited centromere-associated protein-E (CENP-E) at centromeres of all chromosomes, including misaligned chromosomes from aged SAM, demonstrating that CENP-E did not contribute to chromosome misalignments. Notably, both meiotic cohesin proteins located between sister chromatids, REC8 (recombinant 8), STAG3 (stromal antigen 3) and SMC1beta, were remarkably reduced in oocytes from aged SAM. Further, degradation of the cohesin was even more obvious in SAM than in hybrid F1 mice with age, which may explain why SAM are vulnerable to aneuploidy. This natural ageing mouse model shows that defective cohesin coincides with increased incidence of chromosome misalignment and precocious separations of sister chromatids.

Epidemiology of Down syndrome

Down syndrome (DS) is the most commonly identified genetic form of mental retardation and the leading cause of specific birth defects and medical conditions. Traditional epidemiological studies to determine the prevalence, cause, and clinical significance of the syndrome have been conducted over the last 100 years. DS has been estimated to occur in approximately 1 in 732 infants in the United States, although there is some evidence that variability in prevalence of estimates exist among racial/ethnic groups. Progress has been made in characterizing the specific types of chromosome errors that lead to DS and in identifying associated factors that increase the risk of chromosome 21 malsegregation, i.e., advanced maternal age and recombination. Studies to examine the variability of the presence of specific DS-associated birth defects and medical conditions provide evidence for genetic and environmental modifiers. Here, we provide a brief survey of studies that address the current state of the field and suggest gaps in research that can soon be filled with new multidisciplinary approaches and technological advances.

Effects of Granulosa Cell Mitochondria Transfer on the Early Development of Bovine Embryos In Vitro

The objective of this study was to determine the effect of exogenous mitochondria obtained from granulosa cells on the development of bovine embryos in vitro. We classified cumulus oocyte complexes (COCs) as good (G)- and poor (P)-quality oocytes based on cytoplasmic appearance and cumulus characteristics, and assessed mtDNA copy numbers in the G and P oocytes with real-time polymerase chain reaction (PCR). The mitochondria were isolated by fractionation and suspended in mitochondria injection buffer (MIB). Part one of the experiment consisted of the following treatments: (1) G-oocytes + sperm, (2) P-oocytes + mitochondria + MIB + sperm, (3) P-oocytes + MIB + sperm, and (4) P-oocytes + sperm. In part 2, oocytes were parthenogenetically activated. The treatments were: (1) G-oocytes, (2) P-oocytes + mitochondria + MIB, (3) P-oocytes + MIB, and (4) P-oocytes alone. The results indicated a significant difference in mtDNA copy number between G (361 113 +/- 147 114) and P (198 293 +/- 174 178) oocytes (p < 0.01). The rates of morula, blastocyst, and hatched blastocysts derived from P-oocytes + mitochondria were similar to those of G-oocytes, but significantly higher than P-oocytes without exogenous mitochondria in both the ICSI and parthenogenetic activation experiments. We found no difference in blastomere numbers between G-oocytes and P-oocytes + mitochondria in either experiment, but blastomere numbers in these two groups were significantly higher than in P-oocyte groups without exogenous mitochondria. These data suggest that mtDNA content is very important for early embryo development. Furthermore, the transfer of mitochondria from the same breed may improve embryo quality during preimplantation development.

Female reproductive ageing: current knowledge and future trends

Over the past few decades, postponement of childbearing has led to a decrease in family size and increased rates of age-related female subfertility. Age-related decrease in ovarian follicle numbers and a decay in oocyte quality dictate the occurrence of natural loss of fecundity and, ultimately, menopause. The rate of this ovarian ageing process is highly variable among women. Identification of women who have severely decreased ovarian reserve for their age is, therefore, clinically relevant. Endocrine and imaging tests for ovarian reserve relate mainly to the quantitative aspect of ovarian reserve, but their capacity to predict the chances for pregnancy is limited. Genetic factors regulating the size of the follicle pool and the rate of its depletion might be identified in the near future and, possibly, assist the accurate prediction of a woman's reproductive lifespan.

Reproductive ageing in women

The traditional view in respect to female reproduction is that the number of oocytes at birth is fixed and continuously declines towards the point when no more oocytes are available after menopause. In this review we briefly discuss the embryonic development of female germ cells and ovarian follicles. The ontogeny of the hypothalamic-pituitary-gonadal axis is then discussed, with a focus on pubertal transition and normal ovulatory menstrual cycles during female adult life. Biochemical markers of menopausal transition are briefly examined. We also examine the effects of age on female fertility, the contribution of chromosomal abnormalities of the oocyte to the observed decline in female fertility with age and the possible biological basis for the occurrence of such abnormalities. Finally, we consider the effects of maternal age on obstetric complications and perinatal outcome. New data that have the potential to revolutionize our understanding of mammalian oogenesis and follicular formation, and of the female reproductive ageing process, are also briefly considered.

The 3D vascular status of the follicle after HCG administration is qualitatively rather than quantitatively associated with its reproductive competence

BACKGROUND

The objective of this study was to determine whether the vascular status of a single pre-ovulatory follicle is associated quantitatively and/or qualitatively with its reproductive competence.

METHODS

We studied 61 monofollicular IVF-embryo transfer cycles. Just before single oocyte retrieval, follicle vascularization was detected by transvaginal power-Doppler, 3-dimensionally reconstructed, and analysed quantitatively by coloured/gray voxel ratio [vascularization index (VI)] and qualitatively by blood cell displacement [flow index (FI)] calculation. Cycles were sorted in two sets of two groups: low VI (<or=8%, n = 44) and high VI (>8%, n = 17); low FI (<or=30, n = 22) and high FI (>30, n = 39).

RESULTS

Patients' characteristics, fertilization rates, and embryo morphology were comparable in all groups. In contrast, clinical pregnancy rates/oocyte retrieval (4% versus 33%, P < 0.009) and implantation rates (11% versus 50%, P < 0.04) were markedly poorer in the low as compared to the high FI groups, respectively, but remained similar between the low and the high VI groups (22% versus 23% and 38% versus 44%, respectively).

CONCLUSIONS

A qualitative (FI) rather than quantitative (VI) relationship exists between vascular status and functional quality of the follicle after HCG administration.

Power doppler ultrasound assessment of the relationship between age and ovarian perifollicular blood flow in women undergoing in vitro fertilization treatment

PURPOSE

To examine the relationship between age and ovarian perifollicular blood flow (PFBF) in women undergoing IVF.

METHODS

Serial transvaginal power Doppler ultrasound (PDU) scans to assess ovarian PFBF were performed prospectively throughout the follicular phase of ovarian stimulation in women undergoing IVF. The ultrasound assessment days were categorized according to day of hCG trigger.

RESULTS

A total of 1050 ovarian follicles from 34 women undergoing one IVF treatment cycle were used for data analysis. The median age of the women was 38.5 years, ranging from 28 years to 44 years. There was a significant negative correlation between age and ovarian PFBF on the day of hCG trigger or trigger day minus 1, but not beforehand during the follicular phase.

CONCLUSIONS

There was a significant negative correlation between age and ovarian PFBF in women undergoing IVF which was only observed very late in the follicular phase of ovarian stimulation.

Deficit of mitochondria-derived ATP during oxidative stress impairs mouse MII oocyte spindles

Although the role of oxidative stress in maternal aging and infertility has been suggested, the underlying mechanisms are not fully understood. The present study is designed to determine the relationship between mitochondrial function and spindle stability in metaphase II (MII) oocytes under oxidative stress. MII mouse oocytes were treated with H2O2 in the presence or absence of permeability transition pores (PTPs) blockers cyclosporin A (CsA). In addition, antioxidant N-acetylcysteine (NAC), F0/F1 synthase inhibitor oligomycin A, the mitochondria uncoupler carbonyl cyanide 4-trifluoro-methoxyphenylhydrazone (FCCP) or thapsigargin plus 2.5 mM Ca2+ (Th+2.5 mM Ca2+) were used in mechanistic studies. Morphologic analyses of oocyte spindles and chromosomes were performed and mitochondrial membrane potential (DeltaPsim), cytoplasmic free calcium concentration ([Ca2+]c) and cytoplasmic ATP content within oocytes were also assayed. In a time- and H2O2 dose-dependent manner, disruption of meiotic spindles was found after oocytes were treated with H2O2, which was prevented by pre-treatment with NAC. Administration of H2O2 led to a dissipation of DeltaPsim, an increase in [Ca2+]c and a decrease in cytoplasmic ATP levels. These detrimental responses of oocytes to H2O2 treatment could be blocked by pre-incubation with CsA. Similar to H2O2, both oligomycin A and FCCP dissipated DeltaPsim, decreased cytoplasmic ATP contents and disassembled MII oocyte spindles, while high [Ca2+]c alone had no effects on spindle morphology. In conclusion, the decrease in mitochondria-derived ATP during oxidative stress may cause a disassembly of mouse MII oocyte spindles, presumably due to the opening of the mitochondrial PTPs.

Relationship of recombination patterns and maternal age among non-disjoined chromosomes 21

Advancing maternal age has long been identified as the primary risk factor for human chromosome trisomy. More recently, altered patterns of meiotic recombination have been found to be associated with non-disjunction. We have used trisomy 21 as a model for human non-disjunction that occurs during the formation of oocytes to understand the role of maternal age and recombination. Patterns of recombination that increase the risk for non-disjunction of chromosome 21 include absence of any exchange, an exchange near the centromere or a single, telomeric exchange. Our recent work has shown that different susceptibility patterns are associated with the origin of the meiotic error and maternal age. For MI (meiosis I) errors, the proportion of oocytes with susceptible recombination patterns is highest among young mothers and decreases significantly in the oldest age group. In fact, the pattern of exchanges among the oldest age group mimics the pattern observed among normally disjoining chromosomes 21. These results suggest that oocytes of younger women, with functional meiotic apparatus and/or robust ovarian environment, are able to properly resolve all but the most susceptible exchange patterns. As women age, however, meiotic mechanisms erode, making it difficult to resolve even stable exchange events. Interestingly, our preliminary recombination results on MII errors reveal the opposite relationship with maternal age: susceptible pericentromeric exchanges occur most often in the older age group compared with the younger age group. If confirmed, we will have further evidence for multiple risk factors for non-disjunction that act at different times in the meiotic process.

Folate gene polymorphisms and the risk of Down syndrome pregnancies in young Italian women

Maternal impairments in folate metabolism and elevated homocysteinemia are known risk factors for having a child with Down syndrome (DS) at a young age. The 80G>A polymorphism of the reduced folate carrier gene (RFC-1) has been recently demonstrated to affect plasma folate and homocysteine levels, alone or in combination with the 677C>T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene. We performed the present study on 80 Italian mothers of DS individuals, aged less than 35 at conception, and 111 Italian control mothers, to study the role of the RFC-1 80G>A, MTHFR 677C>T, and MTHFR 1298A>C genotypes to the risk of a DS offspring at a young maternal age. When polymorphisms were considered alone, both allele and genotype frequencies did not significantly differ between DS mothers and control mothers. However, the combined MTHFR677TT/RFC-1 80GG genotype was borderline associated with an increased risk (OR 6 (CI 95%: 1.0-35.9), P = 0.05), and to be MTHF1298AA/RFC-1 80(GA or AA) was inversely associated with the risk (OR 0.36 (CI 95%: 0.14-0.96), P = 0.04). Present results seem to indicate that none of the RFC-1 80G>A, MTHFR 677C>T, and MTHFR 1298A>C polymorphisms is an independent risk factor for a DS offspring at a young maternal age; however, a role for the combined MTHFR/RFC-1 genotypes in the risk of DS pregnancies among young Italian women cannot be excluded.

Uterine vascularization and pregnancy outcome in patients undergoing intracytoplasmatic sperm injection: the role of nitric oxide

PURPOSE

To evaluate whether, after pituitary desensitisation, the impedance to flow in the uterine vessels may be an indicator of an ICSI programme outcome, and to test the relationship between intrafollicular nitric oxide and oocyte/embryo quality.

METHODS

Thirty-eight women, on the basis of impedance to flow at the level of uterine artery, evaluated on the first day of COH, were divided in patients with normal (Pulsatility Index--PI, 2.5; Group II, n=27) PI values. The patients were submitted to hormonal, ultrasonographic and Doppler evaluations. Plasma and follicular fluid concentrations of nitrites/nitrate (NO(2) (-)/NO(3) (-)) were assayed.

RESULTS

In the Group I, the impedance to flow remained lower than in Group II and was associated to good quality embryos and to a higher pregnancy rate. Follicular fluid NO(2) (-)/NO(3) (-) levels were inversely correlated with the embryo quality. The uterine artery PI and the pregnancy rate were inversely correlated. The PIs analysed on the day 1 of stimulation, were positively correlated with those registered on day 8 and on the day of ovum pick-up.

CONCLUSIONS

A Doppler analysis done on day 1 of controlled ovarian hyperstimulation may be an useful indicator of ART outcome.

Risk factors for nondisjunction of trisomy 21

The leading cause of Down syndrome (DS) is nondisjunction of chromosome 21 occurring during the formation of gametes. In this review, we discuss the progress made to identify risk factors associated with this type of chromosome error occurring in oogenesis and spermatogenesis. For errors occurring in oocytes, the primary risk factors are maternal age and altered recombination. We review the current progress made with respect to these factors and briefly outline the potential environmental and genetic influences that may play a role. Although the studies of paternal nondisjunction are limited due to the relatively small proportion of errors of this type, we review the potential influence of paternal age, recombination and other environmental and genetic factors on susceptibility. Although progress has been made to understand the mechanisms and risk factors that underlie nondisjunction, considerably more research needs to be conducted to dissect this multifactorial trait, one that has a considerable impact on our species.

Is oocyte morphology prognostic of embryo developmental potential after ICSI?

Metaphase II-stage oocytes collected from patients following ovarian stimulation show varying qualities. Both nuclear and cytoplasmic maturation have to be completed in a co-ordinated mode to ensure optimal conditions for subsequent fertilization. Disturbances or asynchrony of these processes may result in different morphological abnormalities, depending on whether nuclear or cytoplasmic maturation has been affected. In this respect it has been suggested that dysmorphic features occurring early in meiotic maturation may be associated with a higher frequency of aneuploidy and fertilization failure, while those occurring late in maturation may cause a higher incidence of developmental failure. In fact, more than half of the gametes collected show morphological abnormalities, some of which seem to be correlated with an impaired outcome (e.g. aggregation of endoplasmic reticulum, vacuolization, increased ooplasmic viscosity, giant eggs). Therefore, it is strongly recommended to include oocyte quality in all scoring systems applied in IVF laboratories.

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.

Clinical use of the perifollicular vascularity assessment in IVF cycles: a pilot study

BACKGROUND

In Italy, a recent law has imposed a ban on the fertilization of more than three oocytes at one time, and all resulting embryos produced must be transferred simultaneously. The aim of the present controlled study was to assess the clinical feasibility and efficacy of the perifollicular vascularity assessment for oocyte selection in IVF cycles.

METHODS

Fifty-four young primary infertile non-obese women (27 cases and 27 age- and BMI-matched controls) underwent IVF cycles. The choice of the oocytes to fertilize was performed according to perifollicular vascularization in the experimental group, whereas in the control group, the standard morphologic criteria alone were used. The dose of gonadotrophins used, the dominant follicles obtained, the duration of the ovarian stimulation, the number of oocytes retrieved, the number/quality of oocytes fertilized and of cleaved embryos, cycle cancellation, implantation, clinical pregnancy, ongoing pregnancy, multiple pregnancies and ovarian hyperstimulation syndrome rates were assessed in each group.

RESULTS

The assessment of perifollicular vascularity was feasible in 88.9% of cases. No difference between groups was detected in any parameter evaluated.

CONCLUSION

Power Doppler assessment of perifollicular vascularity seems to have no clinical utility for oocyte selection in IVF cycles for young infertile women.

Construction and fertilization of reconstituted human oocytes

Construction of artificial gametes may be made possible by transferring somatic cells into enucleated oocytes and inducing chromosomal halving of their nuclei. This study examines the possibility of constructing viable human gametes, and their potential for participation in normal fertilization. Spare germinal vesicle-stage oocytes were donated by consenting patients undergoing intracytoplasmic sperm injection (ICSI). Approximately 62% of in-vitro matured oocytes survived enucleation and subsequent cumulus cell injection. Following micromanipulation and subsequent activation, about 40% of the reconstituted oocytes yielded two pronuclear-like entities. This was not accompanied by extrusion of a polar body, but resulted in the formation of two 'putative haploid' pronuclei. Therefore selective removal of a female pronucleus marker was required to restore a balanced ploidy. Male pronuclei were identified by association with sperm mitochondria. Additional pronuclei were then removed, allowing further cleavage. Zygotes derived were 'putatively haploid' in approximately 38% of cases with a limited number of chromosomes assessed. However, on karyotypic analysis, blastomeres isolated from cleaving embryos showed a chaotic distribution of chromosomes. Oocytes could induce 'putative haploidization' of transplanted somatic cell nuclei independently of donor cell gender. Fertilization of artificial oocytes was followed by embryonic cleavage despite blastocyst development and chromosomal content possibly being compromised.

The role of aromatase inhibitors in ameliorating deleterious effects of ovarian stimulation on outcome of infertility treatment

Clinical utilization of ovulation stimulation to facilitate the ability of a couple to conceive has not only provided a valuable therapeutic approach, but has also yielded extensive information on the physiology of ovarian follicular recruitment, endometrial receptivity and early embryo competency. One of the consequences of the use of fertility enhancing agents for ovarian stimulation has been the creation of a hyperestrogenic state, which may influence each of these parameters. Use of aromatase inhibitors reduces hyperestrogenism inevitably attained during ovarian stimulation. In addition, the adjunct use of aromatase inhibitors during ovarian stimulation reduces amount of gonadotropins required for optimum stimulation. The unique approach of reducing hyperestrogenism, as well as lowering amount of gonadotropins without affecting the number of mature ovarian follicles is an exciting strategy that could result in improvement in the treatment outcome by ameliorating the deleterious effects of the ovarian stimulation on follicular development, endometrial receptivity, as well as oocyte and embryo quality.

Improving in vitro development of cloned bovine embryos with hybrid (Holstein–Chinese Yellow) recipient oocytes recovered by ovum pick up

In the present study, oocytes from F1 hybrid cattle, as well as their parental lines, were recovered by ovum pick up (OPU) and used as recipient cytoplasm for somatic cell nuclear transfer (SCNT). Four F1 hybrid (Holstein dam x Chinese Yellow sire), 10 Holstein and four Chinese Yellow cattle were subjected to OPU once weekly. There were no significant differences among breeds for number of recovered oocytes per session (overall average, 7.8+/-0.5; mean+/-S.E.M.), quality of the recovered oocytes, or oocyte maturation rate (72-73%). Matured oocytes were all used as recipient cytoplasm (without selection) and a single batch of cumulus cells collected from a Holstein cow were used as donor cells. Although reconstructed embryos initiated cleavage sooner when the recipient cytoplasm was from hybrid cattle versus the two parental breeds, the overall cleavage rate was indistinguishable among breeds. At Day 8, the blastocyst rate from the cleaved embryos (51% versus 37% and 27%), the total number of cells per blastocyst (135+/-4.1 versus 116+/-3.6 and 101+/-4.2), and the percentage of Grade-A (excellent quality) blastocysts (54% versus 42% and 29%) in the hybrid group were all higher than that of Holstein and Yellow groups. Furthermore, the proportion of blastocysts obtained at Day 7 (as a percentage of the total number of blastocysts) was greater in the hybrid group than in Holstein and Yellow groups (89% versus 71% and 63%). In conclusion, the use of F1 hybrid oocytes as recipient cytoplasm significantly improved in vitro development of cloned bovine embryos relative to oocytes derived from the parental lines.

Effect of maternal age on the frequency of cytogenetic abnormalities in human oocytes

The cytogenetic investigation of human oocytes was initiated in the Sixties, and for the last four decades, this field of research has never stopped progressing as new technologies appear. Numerous karyotyping studies and molecular cytogenetic studies have been reported to date, providing a large body of data on the incidence and the distribution of chromosomal abnormalities in human female gametes, but also displaying a great variability in results, which may be essentially attributable to the technical limitations of these in situ methods when applied to human oocytes. Essentially, the most relevant analyses have led to the estimate that 15-20% of human oocytes display chromosome abnormalities, and they have emphasized the implication of both whole chromosome nondisjunction and chromatid separation in the occurrence of aneuploidy in human oocytes. The effect of advanced maternal age on the incidence of aneuploidies has also been investigated in human oocytes. Most previous studies have failed to confirm any relationship between maternal age and aneuploidy frequency in human oocytes, whereas the more recent reports based on large samples of oocytes or polar bodies have provided evidence for a direct correlation between increased aneuploidy frequency and advanced maternal age, and have clarified the contribution of the various types of malsegregation in the maternal age-dependent aneuploidies.

Menopause: why does fertility end before life?

Menopause is associated with an ultimate cessation of child-bearing potential. Medical research on menopause focuses mostly on the underlying physiological changes associated with menopause. By contrast, evolutionary biologists are interested in understanding why women lose their potential to reproduce before the end of their lives. Evolution by natural selection predicts that the behaviors that we observe today are products of generations of selection on the genes that govern those behaviors. Since one would expect an individual reproducing throughout its life to produce more offspring than an individual stopping early, one would seldom expect genes for menopause to be selected for during our evolutionary past. This article discusses how menopause and prolonged lifespan might be explained by evolutionary theory, and highlights some angles for future research.

Bisphenol-A induces cell cycle delay and alters centrosome and spindle microtubular organization in oocytes during meiosis

Bisphenol-A (BPA) is a widely used environmental estrogen-like chemical that has a weak estrogenic activity. This study aimed to test the potential inhibitory effects of BPA on meiotic cell cycle progression, centrosomes and spindle integrity in mouse cumulus-oocyte complexes (COCs). They were exposed to BPA (10-30 microM; 2.3-6.8 ppm) during meiosis-I and the formation of metaphase-II (M-II) spindle. Exposure to BPA during meiosis-I caused a dose-dependent retardation/inhibition of cell cycle progression; 74 and 61% of cells reached metaphase-I (M-I) in the presence of 10 and 30 microM BPA, respectively, (81% in controls, P<0.001). A more striking delay was noted when oocytes were exposed to BPA during the formation of M-II spindle, i.e. 61 and 41% of cells (94% in controls, P<0.001) reached M-II while the remaining cells remained at M-I. Depending on dose, both (i) loosening and elongation of meiotic spindles and (ii) compaction and dispersion of pericentriolar material (PCM) were noted in all samples, all of which resulted in a series of spindle abnormalities. Interestingly, no chromosome was detected in the first polar body after the 10 and 30 microM BPA treatments. When the cells were freed from BPA exposure at 10 and 30 microM, 70 and 61%, of the cells succeeded in reaching M-II (93% in controls, P<0.001), respectively. In conclusion, one mode of action of BPA is a moderately severe yet reversible delay in the meiotic cell cycle, possibly by a mechanism that degrades centrosomal proteins and thus perturbs the spindle microtubule organization and chromosome segregation.

Transfer of germinal vesicle to ooplasm of young mice could not rescue ageing-associated chromosome misalignment in meiosis of oocytes from aged mice

BACKGROUND

[corrected] Transferring a germinal vesicle (GV) from an aged woman's oocyte into ooplasm from a younger woman has been proposed as a possible way to overcome the problem of age-related decline in female fertility. Here we assessed this possibility by determining whether ooplasts derived from young mice could rescue ageing-associated chromosome misalignment in meiosis of oocytes from aged mice.

METHODS

Three groups of reconstructed oocytes, young GV-young cytoplast (group YY), aged GV-young cytoplast (group AY), and young GV-aged cytoplast (group YA), were created by micromanipulation and electrofusion.

RESULTS

Nuclear transplantation was successful in 89.8-94.4% of GV-ooplast complexes, and maturation rate of the reconstructed oocytes was 93.5-97.9%. Confocal microscopy analysis showed a significantly higher rate (49.2%) of chromosome misalignment in ageing mice than in young mice (16.9%), and 57.1% of oocytes in group AY exhibited chromosome misalignment, while the abnormality rate in groups YY and YA was 16.3 and 16.7% respectively. Calcium imaging showed that the three groups of reconstructed oocytes exhibited a similar pattern of calcium oscillations upon stimulation with bovine sperm extracts. Fertilization rate and developmental capacity to 2-cell embryos were also similar among the three groups of oocytes.

CONCLUSIONS

Our findings suggest that: (i) the ooplasm from young mice could not rescue ageing-associated chromosome misalignment in meiosis of GV from aged mice; and (ii) behaviour of chromosome alignment over metaphase spindle is predominantly determined by GV material.

Hyperbaric oxygen and ovarian follicular stimulation for in vitro fertilization: a pilot study

Our objective was to assess the safety and tolerability of hyperbaric oxygen therapy (HBO) as an adjunct to IVF therapy in women with a poor prognosis for pregnancy in a prospective observational pilot study. We conclude that HBO is well tolerated by women undergoing IVF treatment and that further study is required to determine whether this is an efficacious adjuvant therapy for women being treated by IVF.

Effect of Treating Induced Mitochondrial Damage on Embryonic Development and Epigenesis

Germinal vesicle transplantation (GVT) has been proposed as a possible treatment to correct age-related oocyte aneuploidy caused by dysfunctional ooplasm. How healthy ooplasm regulates normal meiosis and subsequent development has yet to be elucidated, but impaired mitochondrial metabolism may be attributable to incomplete segregation of the oocyte chromosomes. In the present study, after ooplasmic mitochondrial damage by photoirradiating chloromethyl-X-rosamine, examination of the oocyte nuclei's ability to survive after transfer into healthy ooplasts was performed. To assess their fertilizability and potential for development, GVT oocytes were fertilized by intracytoplasmic sperm injection (ICSI) and transferred to foster mice. Condition of the offspring at birth was assessed, and epigenetic analysis was performed. Photosensitization consistently inhibited oocyte maturation. However, after GVT of photosensitized nuclei into healthy ooplasts, 67.2% were reconstituted, and 76.2% of these matured normally, with an overall rate of 51.2%, much higher than that (6.0%) in the mitochondrially injured oocytes. After ICSI, 65.8% (52/79) of GVT oocytes were fertilized normally, and 21.1% (11/52) eventually reached the blastocyst stage. The transfer of 132 two-cell GVT embryos into the oviducts of pseudopregnant females resulted in 17 apparently healthy live offspring. For some key developmental genes, a high level of expression was identified in the GVT and "rescue"-derived fetal adnexa. Thus, one can induce in oocyte mitochondria a photosensitization-based type of damage, which consistently inhibits GV breakdown, meiotic spindle formation, chromosomal segregation, and polar body extrusion. Germinal vesicle transplanted and rescued oocytes were able to undergo maturation, fertilization, and embryonic cleavage and, ultimately, to develop to term. This approach may provide a model with which to study the age-related ooplasmic dysfunction seen in human oocytes.

Primary prevention of Down's syndrome

BACKGROUND

Antenatal screening has the capacity to detect more than 90% of Down's syndrome pregnancies leading to therapeutic abortion. Successes in recent years with such so-called 'secondary' prevention have not been matched with progress in primary prevention. Despite considerable research over many decades the principle cause of the disorder is unknown.

METHODS

This paper considers three potential primary prevention strategies, (1) avoiding reproduction at advanced maternal age, (2) pre-implantation genetic diagnosis for couples who are at high risk of Down's syndrome, and (3) folic acid supplementation. The principle aetiological hypotheses are also reviewed.

INTERPRETATION

A strategy of completing the family before a maternal age of 30 could more than halve the birth prevalence of this disorder. Women with a high a priori risk should have access to pre-implantation genetic diagnosis, which can lead to a reasonably high pregnancy rate with an extremely low risk of a Down's syndrome. The evidence suggesting an aetiological role for defective folate and methyl metabolism is not sufficient to justify an active preventative strategy of folic acid supplementation without performing a large clinical trial. Current supplementation policies designed to prevent neural tube defects may incidentally prevent Down's syndrome, provided a sufficiently high dose of folic acid is used. Further progress in primary prevention is hampered by limited aetiological knowledge and there is an urgent need to refocus research in that direction.

The chromosomal analysis of human oocytes. An overview of established procedures

The cytogenetic survey of mature human oocytes has been and remains a subject of great interest because of the prevalence of aneuploidy of maternal origin in abnormal human conceptuses, and the lack of understanding about the non-disjunction processes in human meiosis. The first attempts to analyse the chromosomal content of human female gametes were made in the early 1970s, and led to limited data because of the paucity of materials and the inadequacy of the procedure used. The years to follow brought a resurgence of interest in this field, because of the development of human IVF techniques which made oocytes unfertilized in vitro available for cytogenetic analysis. Numerous studies have since been performed. However, the difficulties in obtaining good chromosome preparations and of performing accurate chromosome identification have reduced the viability of these studies, resulting in large variations in the reported incidences of chromosomal abnormalities. The further introduction of new procedures for oocyte fixation and the screening of large oocyte samples have allowed more reliable data to be obtained and to identify premature chromatid separation as a major mechanism in aneuploidy occurrence. The last decade has been privileged to witness the adaptation of molecular cytogenetic techniques to human oocytes, and thus various powerful procedures have been tried not only on female gametes, but also on polar bodies, involving sequential and multicolour fluorescent in situ hybridization (FISH) labelling, comparative genomic hybridization (CGH), spectral karyotyping and alternative methods such as primed in situ labelling (PRINS) and peptide nucleic acid (PNA) techniques. A large body of data has been obtained, but these studies also display a great variability in the frequency of abnormalities, which may be essentially attributable to the technical limitations of these in situ methods when applied to human oocytes. However, molecular cytogenetic approaches have also evidenced the co-existence of both whole chromosome non-disjunction and chromatid separation in maternal aneuploidy. In addition, the extension of these techniques to oocyte polar body materials has provided additional data on the mechanism of meiotic malsegregation. Improvements of some of these techniques have already been reported. The further development of new approaches for the in situ analysis of human meiosis will increase the impact of cytogenetic investigation of human oocytes in the understanding of aneuploidy processes in humans.

Longitudinal assessment of ovarian perifollicular and endometrial vascularity by power Doppler ultrasound in pregnant and non-pregnant cycles in the IVF setting

PURPOSE

This longitudinal study aimed to compare ovarian perifollicular and endometrial blood flow (PFBF and EBF, respectively) during the follicular phase in pregnant and non-pregnant IVF cycles.

METHODS

Serial transvaginal scans were performed in 15 subjects undergoing IVF treatment. Both PFBF and EBF were subjectively graded (grades 0-4 for PFBF and grades 1-3 for EBF). After confirmation of clinical pregnancy, the treatment cycles were grouped into 'Pregnant' and 'Non-pregnant' cycles. Ovarian PFBF and EBF were retrospectively compared between the two groups.

RESULTS

In pregnant cycles, the proportion of large (> or = 15 mm) follicles with high (24) grade PFBF increased with time throughout the follicular phase, and the proportion of large follicles with poor (0-1) grade PFBF decreased. In non-pregnant cycles these trends were reversed. There was no difference in EBF between the two groups.

CONCLUSION

The pattern of ovarian PFBF but not EBF may be predictive of treatment outcome.

Nuclear Origin of Aging-Associated Meiotic Defects in Senescence-Accelerated Mice1

Factors of both cytoplasmic and nuclear origin regulate metaphase chromosome alignment and spindle checkpoint during mitosis. Most aneuploidies associated with maternal aging are believed to derive from nondisjunction and meiotic errors, such as aberrations in spindle formation and chromosome alignment at meiosis I. Senescence-accelerated mice (SAM) exhibit aging-associated meiotic defects, specifically chromosome misalignments at meiosis I and II that resemble those found in human female aging. How maternal aging disrupts meiosis remains largely unexplained. Using germinal vesicle nuclear transfer, we found that aging-associated misalignment of metaphase chromosomes is predominately associated with the nuclear factors in the SAM model. Cytoplasm of young hybrid B6C3F1 mouse oocytes could partly rescue aging-associated meiotic chromosome misalignment, whereas cytoplasm of young SAM was ineffective in preventing the meiotic defects of old SAM oocytes, which is indicative of a deficiency of SAM oocyte cytoplasm. Our results demonstrate that both nuclear and cytoplasmic factors contribute to the meiotic defects of the old SAM oocytes and that the nuclear compartment plays the predominant role in the etiology of aging-related meiotic defects.

Prenatal diagnosis, pregnancy terminations and prevalence of Down syndrome in Atlanta

BACKGROUND

The impact of prenatal diagnosis on the live birth prevalence of Down syndrome (trisomy 21) has been described. This study examines the prevalence of Down syndrome before (1990-1993) and after inclusion of prenatally diagnosed cases (1994-1999) in a population-based registry of birth defects in metropolitan Atlanta.

METHODS

We identified infants and spontaneous fetal deaths with Down syndrome (n = 387), and pregnancies electively terminated after a prenatal diagnosis of Down syndrome (n = 139) from 1990 to 1999 among residents of metropolitan Atlanta from a population-based registry of birth defects, the Metropolitan Atlanta Congenital Defects Program (MACDP). Only diagnoses of full trisomy 21 were included. Denominator information on live births was derived from State of Georgia birth certificate data. We compared the prevalence of Down syndrome by calendar period (1990-1993, 1994-1999), maternal age (<35 years, 35+ years), and race/ethnicity (White, Black, other), using chi-square and Fisher's exact tests.

RESULTS

During the period when case ascertainment was based only on hospitals (1990-1993), the prevalence of Down syndrome was 8.4 per 10,000 live births when pregnancy terminations were excluded and 8.8 per 10,000 when terminations were included. When case ascertainment also included perinatal offices (1994-1999), the prevalence of Down syndrome was 10.1 per 10,000 when terminations were excluded and 15.3 when terminations were included. During 1990-1993, the prevalence of Down syndrome was 24.7 per 10,000 among offspring to women 35+ years of age compared to 6.8 per 10,000 among offspring to women <35 years of age (rate ratio [RR] = 3.65, 95% confidence interval [CI] = 2.53-5.28). During 1994-1999, the prevalence of Down syndrome was 55.3 per 10,000 among offspring to women 35+ years compared to 8.5 per 10,000 among offspring to women <35 years (RR = 6.55, 95% CI = 5.36-7.99). There was no statistically significant variation in the prevalence of Down syndrome by race/ethnicity within maternal age and period of birth strata. During 1994-1999, the proportion of cases that were electively terminated was greater for women 35+ years compared to women <35 years (RR = 5.10, 95% CI = 3.14-8.28), and lower for Blacks compared to Whites among women 35+ years of age (RR = 0.33, 95% CI = 0.16-0.66).

CONCLUSIONS

In recent years, perinatal offices have become an important source of cases of Down syndrome for MACDP, contributing at least 34% of cases among pregnancies in women 35+ years of age. Variation in the prevalence of Down syndrome by race/ethnicity, before or after inclusion of cases ascertained from perinatal offices, was not statistically significant. Among Down syndrome pregnancies in mothers 35+ years we found a lower proportion of elective termination among Black women compared to White women. We suggest that future reports on the prevalence of Down syndrome by race/ethnicity take into account possible variations in the frequency of prenatal diagnosis or elective termination by race/ethnicity.

Implantation in patients over 40 and raising FSH levels--a review

There is an evident decline of female fertility with age. This decline is mainly due to increased risk of pregnancy termination either after conception or after embryo implantation. Very likely the major cause of this embryo and pregnancy loss is chromosomal aneuploidies caused mostly by increasing rates of 'poor quality' oocytes. This phenomenon can be explained either by an age dependent accumulation of damage and/or by the hypothesis that the defective oocytes are there in the ovaries from the fetal life. 'Good quality' oocytes are ovulated first, leaving 'poor quality' oocytes to be ovulated later in life. Besides the quality of the oocytes which is mainly responsible of the embryo quality (we have not to forget a paternal effect) the process of implantation is dependent upon two variables: the probability of a viable embryo and that of a receptive uterine environment. From the oocyte donation model it seems that the endometrium also plays a minor role in human reproductive ageing as it does in some laboratory animals. However, besides some macroscopic possible causes which may play a role in the reduction of the age-related endometrial receptivity, there are so many endometrial factors possibly related to its receptivity which need to be further studied especially in older women.

Perimenopausal conception

Fertility, defined as the ability to achieve a pregnancy, declines gradually over the woman's lifespan. Although this decline seems to begin from the age of 30 years, it is more obvious between 35 and 40 and increases dramatically thereafter. The age of 41 is considered to be the point when fertility stops and sterility starts. The actual menopause occurs approximately 10 years after the substantial loss of conception potential. Thus, the biological rather than the chronological age of the woman can predict more accurately her fertility potential. This decline in female reproductive potential correlates with ovarian factors, although a slight contribution from the uterus itself and from the neuroendocrine axis cannot be excluded. The ovarian reserve decreases with advancing age, while a parallel decrease in the quality of the oocytes is present, as indicated by the increased incidence of oocyte aneuploidy. The endocrine function of the ovary also declines with age, the later becoming unable to sustain its normal function in the neuroendocrine axis. Additionally, the role of the various endometrial factors remains controversial. On the other hand, exposure to toxic factors and the increased prevalence of infertility-related diseases like endometriosis and PID, may also contribute. Spontaneous conception rates are minimal in perimenopausal women, mainly due to a qualitative and quantitative loss of female gametes. In the rare case of spontaneous conception achievement, complications are more likely. The application of classic ovulation induction and IVF may serve some selected cases, where the woman's ovarian biological age does not correspond to her chronological one. However, the implantation, clinical pregnancy, and live birth rates in women of advanced age undergoing IVF treatment, show very poor results. On the other hand, preimplantation genetic diagnosis is an accurate diagnostic tool for exclusion of genetically deficient embryos prior to embryo transfer. Oocyte donation seems to be the most reliable option of the perimenopausal woman, since the cumulative birth rates after four treatment cycles is approximately 80%. Cryopreservation of ovarian tissue may be an alternative in nulliparas women <40 years of age who want to have children in the future or women with the same desire who, unfortunately, have had pelvic radiotherapy, chemotherapy, oophorectomy, or premature menopause. This technique has given encouraging results in animals, but has not achieved pregnancies in humans. In the future, the use of drugs to block oocyte depletion as well as recent techniques, such as cytoplasmic or germinal vesicle transfer, will be more widely tested and may offer an option to the perimenopausal woman who wishes to conceive.

Socioeconomic effects on the risk of having a recognized pregnancy with Down syndrome

BACKGROUND

Appoximately 95% of Down syndrome (DS) cases are caused by an error in germ cell division (meiosis), resulting in an extra chromosome 21. The meiotic error, predominantly of maternal origin, occurs either during the mother's fetal life (meiosis I) or at ovulation (meiosis II). Because maternal-age-specific DS prevalence rates vary between and within populations, it has been hypothesized that environmental factors can affect the risk for a DS pregnancy.

METHODS

In a population-based case-control study of 997 clinically recognized DS cases (including fetal losses) and 1007 controls without a birth defect, we examined the mother's socioeconomic status (SES) from the time of her fetal life to the time of conception. SES variables were considered as proxies for environmental factors. We used multiple logistic regression for the analyses.

RESULTS

We found associations with low levels of each SES variable examined: mother's education less than high school (OR, 1.29; 95% CI, 1.01-1.65), father's low occupation (OR, 1.23; 95% CI, 0.95-1.60), father's low education (OR, 1.28; 95% CI, 0.99-1.64), mother's father's low occupation (OR, 1.35; 95% CI, 1.06-1.71), and family income <$20,000 (OR, 1.31; 95% CI, 1.02-1.68) [corrected]. The risk for DS increased as the number of low socioeconomic factors present throughout the mother's life increased. With four factors present, the risk (adjusted for confounders) almost doubled (OR, 1.98; 95% CI, 1.30-3.01). Those associations persisted among young (< 30) and old (> or = 30) maternal age groups.

CONCLUSIONS

A mother's low SES during any period before conception increases her risk for a recognized pregnancy with DS. Because of the high birth prevalence of DS, the public health impact of maternal SES may be considerable.

Impact of oxygenation status and patient age on DNA content in cancers of the uterine cervix

PURPOSE

In carcinomas of the uterine cervix, the tumor oxygenation status has been shown to be a prognostic indicator that is independent of treatment modality. In vitro studies suggest gene amplification and polyploidization to be among the major consequences of hypoxia (with or without consecutive reoxygenation) and to be associated with treatment resistance and tumor progression. This study analyzed whether hypoxia alters net DNA content in uterine cervix cancer cells to the extent that it is identifiable by DNA image cytometry.

MATERIALS AND METHODS

In 64 patients with primary cervical cancer, tumor oxygenation was assessed polarographically and correlated with cell DNA content (DNA image cytometry) in areas adjacent to the oxygen microsensor tracks in which oxygenation measurements were made.

RESULTS

No correlation between DNA content (stemline position, Auer classification, and 2c deviation index) and oxygenation status was observed. However, an association between DNA content and patient age and menopausal status was found.

CONCLUSION

Using DNA cytometry, hypoxia-associated genomic changes in uterine cervix cancer cells could not be detected. The impact of tumor hypoxia on the genome may be masked by the effects of alternative mechanisms of genomic instability that can also influence DNA content.