The effects of female age on fecundity and pregnancy outcome

Obstetrical and Perinatal Outcomes Are Not Associated with Advanced Paternal Age in IVF or ICSI Pregnancies with Autologous Oocytes

BACKGROUND

In recent years, there has been an evident delay in childbearing and concerns have been raised about whether this increase in age affects reproductive outcomes. This study aimed to evaluate the effect of paternal age on obstetrical and perinatal outcomes in couples undergoing in vitro fertilization or intracytoplasmic sperm injection using autologous sperm and oocytes.

METHODS

This retrospective study evaluated obstetrical and perinatal outcomes from 14,125 couples that were arbitrarily divided into three groups according to paternal age at conception: ≤30 (n = 1164), 31-40 (n = 11,668) and >40 (n = 1293). Statistics consisted of a descriptive analysis followed by univariate and multivariate models, using the youngest age group as a reference.

RESULTS

The study showed significantly longer pregnancies for the fathers aged 31-40 compared to ≤30 years. However, there were no significant differences for the type of delivery, gestational diabetes, anaemia, hypertension, delivery threat, premature rupture of membranes, preterm birth, very preterm birth, and the neonate's sex, weight, low birth weight, very low birth weight, length, cranial perimeter, Apgar score and neonatal intensive care unit admission.

CONCLUSION

Despite our promising results for older fathers, as paternal age was not associated with clinically relevant obstetrical and perinatal outcomes, future well-designed studies are necessary as it has been associated with other important disorders.

Paraben exposure and couple fecundity: a preconception cohort study

STUDY QUESTION

Is pre-conception exposure to parabens associated with fecundity in couples of childbearing age?

SUMMARY ANSWER

Paraben exposure in female partners was associated with reduced couple fecundity and anti-Müllerian hormone (AMH) might be one of the possible mediators.

WHAT IS KNOWN ALREADY

The reproductive toxicity of parabens, a class of widely used preservatives, has been suggested but evidence regarding their effects on couple fecundity is scarce.

STUDY DESIGN, SIZE, DURATION

In this couple-based prospective cohort study, a total of 884 pre-conception couples who participated in the Shanghai Birth Cohort between 2013 and 2015 were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Concentrations of six parabens were measured in urine samples collected from couples. Malondialdehyde, C-reactive protein, and AMH were assessed in female partners. The outcomes included couple fecundability (time-to-pregnancy, TTP) and infertility (TTP > 12 menstrual cycles). Partner-specific and couple-based models were applied to estimate the associations. The joint effect of paraben mixture on couple fecundity was estimated by quantile-based g-computation (q-gcomp). Mediation analysis was used to assess the mediating roles of oxidative stress, inflammation and ovarian reserve.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 525 couples (59.4%) conceived spontaneously. In the partner-specific model, propyl paraben (PrP), butyl paraben (BuP), and heptyl paraben (HeP) in female partners were associated with reduced fecundability (fecundability odds ratio (95% CI): 0.96 (0.94-0.98) for PrP; 0.90 (0.87-0.94) for BuP; 0.42 (0.28-0.65) for HeP) and increased risk of infertility (rate ratio (95% CI): 1.06 (1.03-1.10) for PrP; 1.14 (1.08-1.21) for BuP; 1.89 (1.26-2.83) for HeP). Similar associations were observed in the couple-based model. AMH played a significant mediation role in the association (average causal mediation effect (95% CI): 0.001 (0.0001-0.003)). Paraben exposure in male partners was not associated with couple fecundity. The joint effect of paraben mixture on couple fecundity was non-significant.

LIMITATIONS, REASONS FOR CAUTION

Self-reported pregnancy and single urine sample may lead to misclassification. The mediation analysis is limited in that levels of sex hormones were not measured. The inclusion of women with irregular menstrual cycles might affect the results. It is possible that the observed association was due to reverse causation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to assess the effects of paraben exposure on couple fecundity in Asians. Given the widespread exposure to parabens in couples of childbearing age, the present findings may have important public health implications.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported in part by the National Natural Science Foundation of China (41991314), the Shanghai Science and Technology Development Foundation (22YF1426700), the Science and Technology Commission of Shanghai Municipality (21410713500), and the Shanghai Municipal Health Commission (2020CXJQ01). All authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Age-associated epigenetic changes in mammalian sperm: implications for offspring health and development

BACKGROUND

Modern reproductive behavior in most developed countries is characterized by delayed parenthood. Older gametes are generally less fertile, accumulating and compounding the effects of varied environmental exposures that are modified by lifestyle factors. Clinicians are primarily concerned with advanced maternal age, while the influence of paternal age on fertility, early development and offspring health remains underappreciated. There is a growing trend to use assisted reproductive technologies for couples of advanced reproductive age. Thus, the number of children born from older gametes is increasing.

OBJECTIVE AND RATIONALE

We review studies reporting age-associated epigenetic changes in mammals and humans in sperm, including DNA methylation, histone modifications and non-coding RNAs. The interplay between environment, fertility, ART and age-related epigenetic signatures is explored. We focus on the association of sperm epigenetics on epigenetic and phenotype events in embryos and offspring.

SEARCH METHODS

Peer-reviewed original and review articles over the last two decades were selected using PubMed and the Web of Science for this narrative review. Searches were performed by adopting the two groups of main terms. The first group included 'advanced paternal age', 'paternal age', 'postponed fatherhood', 'late fatherhood', 'old fatherhood' and the second group included 'sperm epigenetics', 'sperm', 'semen', 'epigenetic', 'inheritance', 'DNA methylation', 'chromatin', 'non-coding RNA', 'assisted reproduction', 'epigenetic clock'.

OUTCOMES

Age is a powerful factor in humans and rodent models associated with increased de novo mutations and a modified sperm epigenome. Age affects all known epigenetic mechanisms, including DNA methylation, histone modifications and profiles of small non-coding (snc)RNA. While DNA methylation is the most investigated, there is a controversy about the direction of age-dependent changes in differentially hypo- or hypermethylated regions with advanced age. Successful development of the human sperm epigenetic clock based on cross-sectional data and four different methods for DNA methylation analysis indicates that at least some CpG exhibit a linear relationship between methylation levels and age. Rodent studies show a significant overlap between genes regulated through age-dependent differentially methylated regions and genes targeted by age-dependent sncRNA. Both age-dependent epigenetic mechanisms target gene networks enriched for embryo developmental, neurodevelopmental, growth and metabolic pathways. Thus, age-dependent changes in the sperm epigenome cannot be described as a stochastic accumulation of random epimutations and may be linked with autism spectrum disorders. Chemical and lifestyle exposures and ART techniques may affect the epigenetic aging of sperm. Although most epigenetic modifications are erased in the early mammalian embryo, there is growing evidence that an altered offspring epigenome and phenotype is linked with advanced paternal age due to the father's sperm accumulating epigenetic changes with time. It has been hypothesized that age-induced changes in the sperm epigenome are profound, physiological and dynamic over years, yet stable over days and months, and likely irreversible.

WIDER IMPLICATIONS

This review raises a concern about delayed fatherhood and age-associated changes in the sperm epigenome that may compromise reproductive health of fathers and transfer altered epigenetic information to subsequent generations. Prospective studies using healthy males that consider confounders are recommended. We suggest a broader discussion focused on regulation of the father's age in natural and ART conceptions is needed. The professional community should be informed and should raise awareness in the population and when counseling older men.

Follicular fluid and blood levels of persistent organic pollutants and reproductive outcomes among women undergoing assisted reproductive technologies

Persistent organic pollutants (POPs) are industrial chemicals resistant to degradation and have been shown to have adverse effects on reproductive health in wildlife and humans. Although regulations have reduced their levels, they are still ubiquitously present and pose a global concern. Here, we studied a cohort of 185 women aged 21-43 years with a median of 2 years of infertility who were seeking assisted reproductive technology (ART) treatment at the Carl von Linné Clinic in Uppsala, Sweden. We analyzed the levels of 9 organochlorine pesticides (OCPs), 10 polychlorinated biphenyls (PCBs), 3 polybrominated diphenyl ethers (PBDEs), and 8 perfluoroalkyl substances (PFASs) in the blood and follicular fluid (FF) samples collected during ovum pick-up. Impact of age on chemical transfer from blood to FF was analyzed. Associations of chemicals, both individually and as a mixture, to 10 ART endpoints were investigated using linear, logistic, and weighted quantile sum regression, adjusted for age, body mass index, parity, fatty fish intake and cause of infertility. Out of the 30 chemicals, 20 were detected in more than half of the blood samples and 15 in FF. Chemical transfer from blood to FF increased with age. Chemical groups in blood crossed the blood-follicle barrier at different rates: OCPs > PCBs > PFASs. Hexachlorobenzene, an OCP, was associated with lower anti-Müllerian hormone, clinical pregnancy, and live birth. PCBs and PFASs were associated with higher antral follicle count and ovarian response as measured by ovarian sensitivity index, but also with lower embryo quality. As a mixture, similar findings were seen for the sum of PCBs and PFASs. Our results suggest that age plays a role in the chemical transfer from blood to FF and that exposure to POPs significantly associates with ART outcomes. We strongly encourage further studies to elucidate the underlying mechanisms of reproductive effects of POPs in humans.

Paternal age effects on sperm FOXK1 and KCNA7 methylation and transmission into the next generation

Children of older fathers carry an increased risk for developing autism and other disorders. To elucidate the underlying mechanisms, we investigated the correlation of sperm DNA methylation with paternal age and its impact on the epigenome of the offspring. Methylation levels of nine candidate genes and LINE-1 repeats were quantified by bisulfite pyrosequencing in sperm DNA of 162 donors and 191 cord blood samples of resulting children (conceived by IVF/ICSI with the same sperm samples). Four genes showed a significant negative correlation between sperm methylation and paternal age. For FOXK1 and KCNA7, the age effect on the sperm epigenome was replicated in an independent cohort of 188 sperm samples. For FOXK1, paternal age also significantly correlated with foetal cord blood (FCB) methylation. Deep bisulfite sequencing and allele-specific pyrosequencing allowed us to distinguish between maternal and paternal alleles in FCB samples with an informative SNP. FCB methylation of the paternal FOXK1 allele was negatively correlated with paternal age, whereas maternal allele was unaffected by maternal age. Since FOXK1 duplication has been associated with autism, we studied blood FOXK1 methylation in 74 children with autism and 41 age-matched controls. The FOXK1 promoter showed a trend for accelerated demethylation in the autism group. Dual luciferase reporter assay revealed that FOXK1 methylation influences gene expression. Collectively, our study demonstrates that age-related DNA methylation changes in sperm can be transmitted to the next generation and may contribute to the increased disease risk in offspring of older fathers.

Time to pregnancy among women with rheumatoid arthritis

OBJECTIVE

To assess whether onset of rheumatoid arthritis (RA) prior to conception is associated with a delayed time to pregnancy (TTP).

METHODS

The study included pregnant women from across Denmark who enrolled in the Danish National Birth Cohort between 1996 and 2002 and had planned or partly planned the cohort pregnancy. RA diagnosis was identified using the Danish National Hospital Discharge Registry. Self-reported data, including TTP, maternal age, parity, prepregnancy height and weight, maternal occupational status, smoking, and alcohol consumption, were collected using a detailed computer-assisted telephone interview at ∼16 weeks of gestation. We used logistic regression analyses as well as a complementary log regression model to examine whether TTP was influenced by RA, adjusting for the abovementioned variables.

RESULTS

Overall, compared with women with no recorded RA (n=74,255), women with prevalent RA (onset prior to conception) (n=112) were slightly older (mean±SD age 30.8±4.3 years versus 29.7±4.1 years), were more likely to have been treated for infertility (9.8% versus 7.6%), and were more likely to have taken>12 months to conceive (25.0% versus 15.6%). The association between RA and TTP was borderline significant after adjusting for covariates in the regression analyses (odds ratio 1.6 [95% confidence interval 1.0-2.4]). Similar results were obtained after restricting the analyses to women who had planned the pregnancy or those who were nulliparous before the cohort pregnancy.

CONCLUSION

Women with RA onset prior to conception had a slightly longer TTP compared with those who did not have RA, indicating a slight reduction in fecundity.

Parental effects on offspring longevity—evidence from 17th to 19th century reproductive histories

BACKGROUND

Family studies provide support for a modest genetic influence on offspring life span, although the magnitude of these correlations is small.

AIM

The study aimed to clarify the relative contributions of parental age at birth and overall parental longevity on offspring lifespan, and to identify the biological and cultural mechanisms.

SUBJECTS AND METHODS

Information was derived from two village genealogies (1650-1927) encompassing 9979 births (5315 males, 4664 females). Data selection was guided by the inclusion of information about parental age at birth and lifespan, offspring lifespan and cohort-specific life expectancy.

RESULTS

Parental age at reproduction displayed a negative association with offspring survivability, which was caused by a host of biological as well as environmental factors. In contrast, parental lifespan was positively associated with offspring age at death. These effects differed by parent's and child's sex.

CONCLUSION

The maternal age effect on female progeny is thought to be indicative of a preferential genetic load. From an evolutionary point of view, direct selection for maternal lifespan may be an adaptive strategy to enhance child survival prospects.

Rising follicle-stimulating hormone levels with age accelerate female reproductive failure

Rising serum FSH levels is one of the earliest signs of human female reproductive aging. Whether or not elevated FSH remains a passive reflection of a diminishing ovarian follicle pool or actively contributes to declining female fertility with age has not been established. We therefore investigated female reproduction in mice expressing progressively rising serum levels of transgenic human FSH (Tg-FSH, 2.5-10 IU/liter) independently of follicle depletion. We show that serum LH and estradiol levels and uterine size remained normal in Tg-FSH females, whereas ovarian weight and corpora lutea number were significantly increased up to 1.3- and 5-fold, respectively. Furthermore, the monotrophic FSH rise produced a striking biphasic effect on female fertility. Tg-FSH females less than 22 wk old delivered increased litter sizes, then beyond 23 wk, litter sizes decreased rapidly culminating in premature infertility despite continued ovary follicle development, and increased ovulation and uterine embryo implantation sites as well as normal serum levels of anti-Mullerian hormone, a marker of ovarian follicle reserve. We found that rising circulating Tg-FSH produced premature infertility by increasing embryo-fetal resorption and parturition failure with age. Thus, our Tg-FSH mice present a novel paradigm to investigate selective contributions of elevated FSH to age-related female infertility, which revealed that rising FSH levels, despite no exhaustion of ovarian reserve, actively accelerates female reproductive aging primarily by postimplantation reduction of embryo-fetal survival.

Debate: do upper age limits need to be imposed on women receiving assisted reproduction treatment?

The inability of local National Health Service trusts to uniformly provide assisted reproduction technology (ART) services has resulted in what has come to be known as a 'postcode lottery'. Older women and those with responsibility for children at home, often have to fund their own treatment. Recently, with the birth of babies to much older women, the mass media have debated whether those past menopausal age should be helped to achieve a pregnancy in this way. We argue that the time is right for interested professionals to enter the debate, especially in view of proposed revisions to the Human Fertilisation & Embryology Authority's code of conduct which requires clinics providing ART to consider the 'welfare of the child'. With that change in mind, we set out the case for imposing upper age limits on those receiving ART in the United Kingdom.

Data collection from very low birthweight infants in a geographical region: methods, costs, and trends in mortality, admission rates, and resource utilisation over a five-year period

AIMS

1. To determine the survival and morbidity of infants at discharge with a birthweight of less than 1500 g in the geographically defined population of East Anglia. 2. To demonstrate a cost-effective method of regional data collection. 3. To determine whether there were any changes in the demand for neonatal care.

STUDY DESIGN AND SUBJECTS

A prospective cohort analysis using a single database to collect data on 1244 very low birthweight infants from eight neonatal units in one Region from 1993 to 1997.

RESULTS

Estimated ascertainment of VLBW infants to the study was 96%. Over the 5 years survival rates were stable (75-79%). 52% of deaths in infants admitted for neonatal care occurred on day 1, with just 15% of deaths occurring after 28 days of life. Mortality risk significantly decreased with increasing gestational age at birth. Compared to 22-25-week old infants, the mortality risk decreased by 65% for 26-27-week old infants (OR 0.35 95% CI (0.21, 0.59)) and by 92% for 32-39-week old infants (OR 0.08 95% CI (0.03, 0.21)) with intermediate odds ratios of 0.22 (0.12, 0.42) and 0.13 (0.06, 0.28) for the 28-29 and 30-39 weeks gestation, respectively. Higher birthweight, after adjusting for gestation also decreased the mortality risk (OR 0.78 per 100 g difference, 95% CI (0.71, 0.86)). No change was seen in the number of extremely preterm infants admitted for intensive care or resource utilisation, although a significant increase was seen in the number of infants dying in delivery rooms. There was a reduction in the reported incidence of pulmonary interstitial emphysema (10-4%) but no change in the number of ventilation days or the rate of chronic lung disease. The mean maternal age increased from 27.7 years to 28.9 years during the study. Maternal steroid administration increased (30% to 59%) and was associated with a decreased risk of mortality (OR 0.44, 95% CI: 0.31-0.62).

CONCLUSIONS

It is possible to collect useful data from the neonatal period at a reasonable cost from a geographically defined population. This information was used for informing clinicians, counselling parents and in the era of managed clinical networks will be useful in guiding the provision of effective health care resources.