Sperm counts and sperm sex ratio in male infertility patients

The Impact of Lifestyle on the Secondary Sex Ratio: A Review

The secondary sex ratio (SSR), indicating the ratio of male to female live births, has garnered considerable attention within the realms of reproductive biology and public health. Numerous factors have been posited as potential trendsetters of the SSR. Given the extensive research on the impact of daily behaviors and habits on individuals' reproductive health, there is a plausible suggestion that lifestyle choices may also influence the SSR. By synthesizing the existing literature on the current research field, this comprehensive review indicates that an elevated SSR has been associated with an increased intake of fatty acids and monosaccharides, proper nutrition, higher educational levels, financial prosperity, and favorable housing conditions. On the other hand, a decreased SSR may be linked to undernutrition, socioeconomic disparities, and psychological distress, aligning with the Trivers-Willard hypothesis. Occupational factors, smoking habits, and cultural beliefs could also contribute to trends in the SSR. Our review underscores the significance of considering the aforementioned factors in studies examining the SSR and emphasizes the necessity for further research to unravel the mechanisms underpinning these connections. A more profound comprehension of SSR alterations due to lifestyle holds the potential to adequately develop public health interventions and healthcare strategies to enhance reproductive health and overall well-being.

Income, stress, and sex ratios over 1895-2010

The medical literature has shown that populations under high stress have a lower sex ratio at birth (i.e. number of males for every 100 females). In this paper, I examine the relationship between income, as a source of economic stress, and the sex ratio at a subnational level for the 1895-2010 period. For this, I use census microdata from Argentina -a developing country that experienced rapid growth at the end of the 19th century and stagnated in recent decades- and I estimate from a two-way fixed effects model that exploits the wide temporal and geographic variability in income. The results show that as per capita income increases, the sex ratio at birth also increases. In particular, for every US$ 1,000 increase in per capita income, the sex ratio increases between 0.3 and 0.6 points. These findings make it possible to quantify the lost boys (i.e. those boys who were not born due to high economic stress on their parents) and constitute a call for attention in favor of the implementation of prenatal care policies -especially in periods of stagnation or income decline- to maintain a more balanced sex ratio.

The Impact of Obesity on Sperm Parameters in Young Adult Males: A Retrospective Study of Sperm Donors

OBJECTIVE

To utilize a large cohort of healthy sperm bank donors to evaluate the association between body mass index and individual sperm parameters.

METHODS

Sperm parameters from donors across the United States were obtained between 2013 and 2022. Donors were healthy men aged 18-46years old. Semen samples were analyzed in a certified lab following guidelines by the World Health Organization. A multivariable interaction model between age, body mass index, and sperm parameters was conducted.

RESULTS

There were 117,357 sperm donations included in our study. In our sample, 98,397 (83.84%) men were classified as young donors (ages 18-32years) and 18,960 (16.16%) were classified as old donors (ages 33-46years). We identified 1032 (0.88%) men as underweight, 76,635 (65.30%) as normal weight, 36,686 (31.26%) as overweight, and 3004 (2.56%) as obese. Participants had a median total motile sperm count (TMSC) of 186 (interquartile ranges [IQR]: 128 million), volume of 3.36 (IQR: 1.82 mL), sperm concentration of 56 (IQR: 34 million/mL) and a progressive motility of 59.84% (IQR: 16.95%). Older obese donor had lower TMSC (β = -22.98 ± 4.66, P < .001), semen volumes (β = -0.85 ± 0.06, P < .001), and progressive motility (β = -3.94 ± 0.56, P < .001) compared to younger, healthy weight donors.

CONCLUSION

We observed lower TMSC, semen volumes, and progressive motility in older obese donors. Although these values are within the normal expected ranges for individual sperm parameters, our ability to detect differences within this healthy population highlights the importance of maintaining a healthy diet and exercise regimen for preserving high sperm counts.

Male infertility

Clinical infertility is the inability of a couple to conceive after 12 months of trying. Male factors are estimated to contribute to 30-50% of cases of infertility. Infertility or reduced fertility can result from testicular dysfunction, endocrinopathies, lifestyle factors (such as tobacco and obesity), congenital anatomical factors, gonadotoxic exposures and ageing, among others. The evaluation of male infertility includes detailed history taking, focused physical examination and selective laboratory testing, including semen analysis. Treatments include lifestyle optimization, empirical or targeted medical therapy as well as surgical therapies that lead to measurable improvement in fertility. Although male infertility is recognized as a disease with effects on quality of life for both members of the infertile couple, fewer data exist on specific quantification and impact compared with other health-related conditions.

Unboxing Industry-Standard AI Models for Male Fertility Prediction with SHAP

Infertility is a social stigma for individuals, and male factors cause approximately 30% of infertility. Despite this, male infertility is underrecognized and underrepresented as a disease. According to the World Health Organization (WHO), changes in lifestyle and environmental factors are the prime reasons for the declining rate of male fertility. Artificial intelligence (AI)/machine learning (ML) models have become an effective solution for early fertility detection. Seven industry-standard ML models are used: support vector machine, random forest (RF), decision tree, logistic regression, naïve bayes, adaboost, and multi-layer perception to detect male fertility. Shapley additive explanations (SHAP) are vital tools that examine the feature's impact on each model's decision making. On these, we perform a comprehensive comparative study to identify good and poor classification models. While dealing with the all-above-mentioned models, the RF model achieves an optimal accuracy and area under curve (AUC) of 90.47% and 99.98%, respectively, by considering five-fold cross-validation (CV) with the balanced dataset. Furthermore, we provide the SHAP explanations of existing models that attain good and poor performance. The findings of this study show that decision making (based on ML models) with SHAP provides thorough explanations for detecting male fertility, as well as a reference for clinicians for further treatment planning.

Preconception Antidiabetic Drugs in Men and Birth Defects in Offspring : A Nationwide Cohort Study

BACKGROUND

Diabetes reduces semen quality and increasingly occurs during reproductive years. Diabetes medications, such as metformin, have glucose-independent effects on the male reproductive system. Associations with birth defects in offspring are unknown.

OBJECTIVE

To evaluate whether the risk for birth defects in offspring varies with preconceptional pharmacologic treatment of fathers with diabetes.

DESIGN

Nationwide prospective registry-based cohort study.

SETTING

Denmark from 1997 to 2016.

PARTICIPANTS

All liveborn singletons from mothers without histories of diabetes or essential hypertension.

MEASUREMENTS

Offspring were considered exposed if their father filled 1 or more prescriptions for a diabetes drug during the development of fertilizing sperm. Sex and frequencies of major birth defects were compared across drugs, times of exposure, and siblings.

RESULTS

Of 1 116 779 offspring included, 3.3% had 1 or more major birth defects (reference). Insulin-exposed offspring (n = 5298) had the reference birth defect frequency (adjusted odds ratio [aOR], 0.98 [95% CI, 0.85 to 1.14]). Metformin-exposed offspring (n = 1451) had an elevated birth defect frequency (aOR, 1.40 [CI, 1.08 to 1.82]). For sulfonylurea-exposed offspring (n = 647), the aOR was 1.34 (CI, 0.94 to 1.92). Offspring whose fathers filled a metformin prescription in the year before (n = 1751) or after (n = 2484) sperm development had reference birth defect frequencies (aORs, 0.88 [CI, 0.59 to 1.31] and 0.92 [CI, 0.68 to 1.26], respectively), as did unexposed siblings of exposed offspring (3.2%; exposed vs. unexposed OR, 1.54 [CI, 0.94 to 2.53]). Among metformin-exposed offspring, genital birth defects, all in boys, were more common (aOR, 3.39 [CI, 1.82 to 6.30]), while the proportion of male offspring was lower (49.4% vs. 51.4%, P = 0.073).

LIMITATION

Information on underlying disease status was limited.

CONCLUSION

Preconception paternal metformin treatment is associated with major birth defects, particularly genital birth defects in boys. Further research should replicate these findings and clarify the causation.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Comparing the Effect of Different Antibiotics in Frozen-Thawed Ram Sperm: Is It Possible to Avoid Their Addition?

It is crucial to perform a deep study about the most extensively used antibiotics in sperm extenders. Most of the protocols and concentrations used in ram are direct extrapolations from other species. It is important to establish species-specific antibiotic treatments to optimize their use and if it is possible to reduce the quantity. Previews studies have assessed some aspects of sperm quality in vitro, but this study aimed to go further and assess the effect of three different antibiotic treatments, which are the most extensively used, not only in sperm quality or assessing the inhibitory effect on bacterial growth but also assessing these important parameters of productivity such as fertility, prolificacy, fecundity, and sex-ratio during a freeze-thaw process. Gentamicyn (G) treatment showed the worst results, not only concerning sperm quality but also in the reproductive trials exhibiting a toxical effect at the experiment concentration, and being the most powerful inhibiting bacterial growth. For its part, Lincomicyn-spectinomycin (LS) showed similar results inhibiting bacterial growth but it did not show a detrimental effect either in sperm quality or in reproductive parameters. Penicillin-streptomycin (PS) showed good results in the sperm quality and in the reproductive in vivo trials, but it showed a very poor effect inhibiting bacterial growth probably due to some kind of antibiotic resistance. According to our results, there is not a significant positive relationship between the higher bacterial inhibitory activity of LS and PS samples, and the sperm quality respect Control samples (without antibiotics). In the case of G, which exhibited the most effective as antibacterial, we observed a toxic effect on sperm quality that could be translated on productivity parameters. Our results suggest that the bacterial contamination control in frozen-thawed semen may be possible without the use of antibiotics, although the effects of longer periods of cooling storage and different temperatures of storage need to be further investigated for animal semen. At this point, a reflection about a drastic reduction in the use of antibiotic treatments in sperm cryopreservation is mandatory, since freezing conditions could keep sperm doses contamination within the levels recommended by regulatory health agencies.

New Biological Insights on X and Y Chromosome-Bearing Spermatozoa

A spermatozoon is a male germ cell capable of fertilizing an oocyte and carries genetic information for determining the sex of the offspring. It comprises autosomes and an X (X spermatozoa) or a Y chromosome (Y spermatozoa). The origin and maturation of both X and Y spermatozoa are the same, however, certain differences may exist. Previous studies proposed a substantial difference between X and Y spermatozoa, however, recent studies suggest negligible or no differences between these spermatozoa with respect to ratio, shape and size, motility and swimming pattern, strength, electric charge, pH, stress response, and aneuploidy. The only difference between X and Y spermatozoa lies in their DNA content. Moreover, recent proteomic and genomic studies have identified a set of proteins and genes that are differentially expressed between X and Y spermatozoa. Therefore, the difference in DNA content might be responsible for the differential expression of certain genes and proteins between these cells. In this review, we have compiled our present knowledge to compare X and Y spermatozoa with respect to their structural, functional, and molecular features. In addition, we have highlighted several areas that could be explored in future studies in this field.

Exposure to male-dominated environments during development influences sperm sex ratios at sexual maturity

Different stages during development are important when it comes to phenotypic adjustments in response to external stimuli. Critical stages in mammals are the prenatal phase, where embryos are exposed to a milieu of sex steroid hormones, and the early-postnatal phase, where littermates interact and experience their incipient social environment. Further, the postmaternal environment will influence the development of traits that are linked to reproductive success in adulthood. Accumulated evidence of male-driven sex allocation establishes the currently untested hypothesis that the sperm sex ratio is a plastic trait that can be mediated to align with prevailing social conditions. Here, we used natural variation in the maternal environment and experimentally manipulated the postmaternal environment to identify the importance of these developmental phases on sperm sex ratio adjustments in wild house mice (Mus musculus domesticus). We found that male density in both environments was predictive of sperm sex ratios at sexual maturity: males from more male-biased litters and males maturing under high male density produced elevated levels of Y-chromosome-bearing sperm. Our findings indicate that the sperm sex ratio is a variable phenotypic trait that responds to the external environment, and highlight the potential that these adjustments function as a mechanism of male-driven sex allocation.

Effects of obesity on sperm retrieval, early embryo quality and clinical outcomes in men with nonobstructive azoospermia undergoing testicular sperm aspiration-intracytoplasmic sperm injection cycles

The objective of this study was to assess the effects of body mass index (BMI) on sperm retrieval, early embryo quality and clinical outcomes in patients with nonobstructive azoospermia (NOA) undergoing testicular sperm aspiration-intracytoplasmic sperm injection (TESA-ICSI). A total of 3,005 infertile couples were evaluated between January 2010 and June 2017, including 1585 normal-weight (BMI < 25 kg/m² ), 847 overweight (BMI 25-29.99 kg/m² ) and 573 obese (BMI ≥ 30 kg/m² ) patients. We found no significant relationship between BMI and sperm retrieval rate (22.4%, 24.3% and 25.1%, p = 0.327) or sperm motility. Among the 705 patients with NOA who underwent TESA-ICSI cycles, obese individuals had lower T levels and higher E2 levels than normal-weight and overweight individuals. However, there were no significant differences in other male hormones (follicle stimulating hormone [FSH], luteinizing hormone [LH], or prolactin [PRL]) among the groups. We also found that the sperm parameters, embryo quality and clinical outcomes of patients with NOA undergoing TESA-ICSI were not influenced by high BMI levels. In conclusion, this study demonstrated a lack of obvious effects of obesity on sperm retrieval, early embryo quality and clinical outcomes in infertile men undergoing TESA-ICSI cycles, although T and E2 levels were affected.

The use of intracytoplasmic sperm injection is associated with a shift in the secondary sex ratio

RESEARCH QUESTION

What is the association between assisted reproductive technologies and human sex ratio as a proportion of male offspring at birth.

DESIGN

A total of 59,628 singleton deliveries resulting from IVF, intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) or ovulation induction from 101 IVF clinics in Germany, that had been documented in a national German IVF registry, were analysed. Sex ratio after assisted reproductive technology was also compared with the sex ratio reported in the birth records of the German Federal Statistical Office.

RESULTS

The sex ratio was 50.0% (95% CI 49.5% to 50.5%) for ICSI, 52.2% (95% CI 51.5% to 52.9%) for IVF, 52.2% (95% CI 50.9% to 53.5%) for IUI or ovulation induction and 51.3% in the national birth records, respectively. Significant differences existed across the three treatment groups (P = 6.86 × 10^-7) as well as in pairwise comparisons between ICSI versus IVF (P = 6.88 × 10^-7) and ICSI versus IUI or ovulation induction (P = 0.003). No difference existed between the groups IUI or ovulation induction versus IVF. Same results were also present after stratification by maternal age: IVF versus ICSI (P = 6.433 × 10^-7), ICSI versus IUI or ovulation induction (P = 0.003), and IVF versus IUI or ovulation induction (non-significant). Compared with the national birth records, ICSI is associated with a lower sex ratio compared with the reference group (P < 0.001), whereas IVF is associated with a higher sex ratio (P = 0.015).

CONCLUSIONS

The use of ICSI is associated with an equal proportion of sexes at birth, which is not the case for IVF, IUI or ovulation induction, or natural conception. This phenomenon is not influenced by maternal age.

Human semen quality and the secondary sex ratio

The aim of this study was to evaluate the association between semen quality and the secondary sex ratio (SSR), defined as the ratio of male to female live births. Our study cohort comprised 227 male partners who were enrolled prior to conception in Michigan and Texas between 2005 and 2009, and prospectively followed through delivery of a singleton birth. The male partners provided a baseline and a follow-up semen sample a month apart. Semen analysis was conducted to assess 27 parameters including five general characteristics, six sperm head measures, 14 morphology measures, and two sperm chromatin stability assay measures. Modified Poisson regression models with a robust error variance were used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of a male birth for each semen parameter, after adjusting for potential confounders. Of the 27 semen parameters, only the percentage of bicephalic sperm was significantly associated with the SSR (2^ndvs 1^st quartile, RR, 0.65, 95% CI, 0.45–0.95, P = 0.03; 4^thvs 1^st quartile, RR, 0.61, 95% CI, 0.38–1.00, P < 0.05 before rounding to two decimal places), suggestive of a higher percentage of bicephalic sperm being associated with an excess of female births. Given the exploratory design of the present study, this preconception cohort study suggests no clear signal that human semen quality is associated with offspring sex determination.

Effects of Electromagnetic Waves Emitted from 3G+Wi-Fi Modems on Human Semen Analysis

Objective

The purpose of this study was to evaluate the effects of 3G+wifi modems on human sperm quality. A total of 40 semen specimens were gathered between March and September 2015, from healthy adult men.

Methods

The sperm samples were divided into two groups – 3G+wi-fi exposed and unexposed groups. In the unexposed group, the specimens were shielded by aluminum foil in three layers and put into an incubator at a temperature of 37°C for 50 minutes. The exposed group was positioned in another room in an incubator at a temperature of 37°C for 50 minutes. A 3G+wi-fi modem was put into the same incubator and a laptop computer was connected to the modem and was downloading for the entire 50 minutes. Semen analysis was done for each specimen and comparisons between parameters of the two groups were done by using Kolmogorov-Smirnov study and a paired t-test.

Results

Mean percentage of sperm with class A and B motility were not significantly different in two groups (p = 0.22 and 0.54, respectively). In class C, it was significantly lower in the exposed group (p = 0.046), while in class D it was significantly higher (p = 0.022). Velocity curvilinear, velocity straight line, velocity average path, mean angular displacement, lateral displacement and beat cross frequency were significantly higher in the unexposed group. The limitation was the in vitro design.

Conclusions

Electromagnetic waves (EMWs) emitted from 3G+wi-fi modems cause a significant decrease in sperm motility and velocity, especially in non-progressive motile sperms. Other parameters of semen analysis did not change significantly. EMWs, which are used in communications worldwide, are a suspected cause of male infertility. Many studies evaluated the effects of cell phones and wi-fi on fertility. To our knowledge, no study has yet been done to show the effects of EMWs emitted from 3G+wi-fi modems on fertility. Our study revealed a significant decrease in the quality of human semen after exposure to EMWs emitted from 3G+wi-fi modems.

Does exposure to inhalation anesthesia gases change the ratio of X-bearing sperms and Y-bearing Sperms? A worth exploring project into an uncharted domain

According to recent surveys performed in United States and India, anesthesia care providers were observed to have sired female offspring in a higher proportion than male offspring as their firstborn progeny; however, the reasons for the skew are not clear. Our hypothesis is that the underlying biological evidence may be elucidated by unraveling differences (if any) between the concentrations of X-bearing sperms and Y-bearing sperms in the semen samples obtained from males exposed to varied levels of anesthetics in their lifetimes. Therefore, the objectives of the envisaged study would be to conduct a three-stage investigative study on in-vitro human semen samples to determine (a) X-bearing sperms and Y-bearing sperms concentrations' ratio in male pediatric anesthesia care providers' semen samples, (b) changes in X-bearing sperms and Y-bearing sperms concentrations' ratios between the pre-rotation and post-rotation semen samples of male medical student volunteers/observers, and (c) changes in X-bearing sperms and Y-bearing sperms concentrations' ratios between the pre-operative and post-operative day-3 semen samples of male patients presenting for outpatient procedures under inhalational anesthesia. The expected outcomes would be (a) linear and positive correlation of the anesthetic gas usage (exposure) with increased X-bearing sperms/Y-bearing sperms ratio in post-anesthesia day 3 sample as compared to the baseline preoperative sample, (b) linear and positive correlation of the anesthetic gas usage (exposure) with increased X-bearing sperms/Y-bearing sperms ratio in post-rotation sample as compared to the baseline sample, and (c) observation of high X-bearing sperms/Y-bearing sperms ratio in the pediatric anesthesia care providers. In summary, effects (if any) of occupational or personal exposure to inhalational anesthetic gases on the X-bearing sperms and Y-bearing sperms ratio is a worthy project wherein lots of questions that have arisen over decades could find the path to their definitive answers, based on envisaged laboratory investigations into this uncharted domain.

Male Reproductive Disorders and Fertility Trends: Influences of Environment and Genetic Susceptibility

It is predicted that Japan and European Union will soon experience appreciable decreases in their populations due to persistently low total fertility rates (TFR) below replacement level (2.1 child per woman). In the United States, where TFR has also declined, there are ethnic differences. Caucasians have rates below replacement, while TFRs among African-Americans and Hispanics are higher. We review possible links between TFR and trends in a range of male reproductive problems, including testicular cancer, disorders of sex development, cryptorchidism, hypospadias, low testosterone levels, poor semen quality, childlessness, changed sex ratio, and increasing demand for assisted reproductive techniques. We present evidence that several adult male reproductive problems arise in utero and are signs of testicular dysgenesis syndrome (TDS). Although TDS might result from genetic mutations, recent evidence suggests that it most often is related to environmental exposures of the fetal testis. However, environmental factors can also affect the adult endocrine system. Based on our review of genetic and environmental factors, we conclude that environmental exposures arising from modern lifestyle, rather than genetics, are the most important factors in the observed trends. These environmental factors might act either directly or via epigenetic mechanisms. In the latter case, the effects of exposures might have an impact for several generations post-exposure. In conclusion, there is an urgent need to prioritize research in reproductive physiology and pathophysiology, particularly in highly industrialized countries facing decreasing populations. We highlight a number of topics that need attention by researchers in human physiology, pathophysiology, environmental health sciences, and demography.

Effect of semen quality on human sex ratio in in vitro fertilization and intracytoplasmic sperm injection: an analysis of 27,158 singleton infants born after fresh single-embryo transfer

OBJECTIVE

To evaluate the effect of semen quality on human sex ratio in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

DESIGN

Retrospective cohort study.

SETTING

Not applicable.

PATIENT(S)

A total of 27,158 singleton infants born between 2007 and 2012 after fresh single-embryo transfer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Proportion of male infants among liveborn infants.

RESULT(S)

There were 14,996 infants born after IVF, 12,164 infants born after ICSI with ejaculated sperm, and 646 infants born after ICSI with nonejaculated sperm. The sex ratio of IVF was 53.1% (95% confidence interval [CI], 52.3-53.9); the sex ratio of ICSI with ejaculated and nonejaculated sperm demonstrated as statistically significant reduction (48.2%; 95% CI, 47.3-49.1 and 47.7%; 95% CI, 43.8-51.6, respectively). In IVF, lower sperm motility, including asthenozoospermia (sperm motility <40%), was associated with a statistically significantly lower sex ratio compared with normal sperm (51.0%; 95% CI, 48.6-53.3 vs. 53.4%; 95% CI, 52.5-54.3). In ICSI with ejaculated sperm, there was no association between sperm motility and sex ratio. Sperm concentration was not associated with sex ratio in both IVF and ICSI.

CONCLUSION(S)

In IVF, lower sperm motility was associated with a statistically significant reduction in sex ratio; ICSI with either ejaculated or nonejaculated sperm was associated with a statistically significant reduction in sex ratio regardless of semen quality.