Recurrent pregnancy loss (RPL), defined as two or more failed clinical pregnancies, affects 1%-3% of couples trying to conceive. Nowadays up to 50% of cases remain idiopathic. In this context, paternal factors evaluation is still very limited. The aim is to address the topic of the male factor in RPL with a broad approach, analyzing collectively data on sperm DNA fragmentation (SDF) and semen parameters. We systematically searched in Pubmed/MEDLINE and Google Scholar from inception to February 2023. A protocol has been registered on PROSPERO (ID number CRD42022278616). PRISMA guidelines were followed.
Methods
Pooled results from 20 studies revealed a higher DNA fragmentation rate in the RPL group compared to controls (mean difference [MD] 9.21, 95% CI 5.58-12.85, p < 0.00001, I2 98%). Age, body mass index (BMI), smoking, and alcohol intake were not associated with DNA fragmentation. Subgroup analysis by different SDF assays (TUNEL and COMET at a neutral pH vs. indirect assessment with other assays) and ethnicity did not highlight different results (p = 0.25 and 0.44).
Results
Results pooled from 25 studies showed a significant difference comparing RPL and control groups regarding ejaculation volume (MD -0.24, 95% CI -0.43; -0.06, p 0.01, I2 66%), total sperm number (MD -10.03, 95% CI -14.65; -5.41, p < 0.0001, I2 76%), total sperm motility (MD -11.20, 95% CI -16.15; -6.25, p < 0.0001, I2 96%), progressive sperm motility (MD -7.34, 95% CI -10.87; -3.80, p < 0.0001, I2 97%), and normal sperm morphology (MD -5.99, 95% CI -9.08; -2.90, p 0.0001, I2 98%). A sub-analysis revealed that Asian and Africans, but not white-European RPL men had lower progressive sperm motility compared to controls.
Conclusion
In conclusion, current review and meta-analysis findings suggested that SDF and some specific semen parameters were associated with RPL in a multi-ethnic evaluation. This effort opens future direction on a growing awareness of, first, how the male factor plays a key role and, second, how appropriate would be to establish a direct dialogue between the gynecologist and the urologist.
Patient Summary
We performed a systematic review and meta-analysis on the male component of RPL. We found that sperm DNA fragmentation and some specific sperm parameters are significantly associated with RPL.
Ponce MR et al., 2026·Andrology·Free full text on PubMed Central
Transgender individuals assigned male at birth (AMAB) may choose to preserve their fertility prior to starting gender-affirming hormone therapy (GAHT). However, limited data exist regarding the baseline reproductive and hormonal characteristics of this population before and after GAHT.
To characterize semen quality and hormonal profiles in transgender AMAB individuals prior to GAHT and compare findings with cisgender men and with transgender individuals who discontinued GAHT for at least 3 months.
This retrospective study included transgender AMAB individuals from two tertiary andrology centers who underwent sperm cryopreservation before GAHT initiation (treatment-naïve group). Clinical evaluation included anthropometric measures, testicular volume assessment, varicocele detection, and sex hormone measures. Semen parameters were analyzed according to WHO criteria and compared with those of cisgender men and previously treated transgender individuals.
Thirty-two treatment-naïve transgender AMAB individuals were included. Hormonal parameters were generally within reference ranges. Only 46.9% of treatment-naïve individuals met WHO criteria for normozoospermia, compared with 75.5% of cisgender controls. Compared with nine previously treated individuals, estradiol levels were higher and seminal volume lower. A higher frequency of seminal abnormalities was observed, although not statistically significant.
A substantial proportion of treatment-naïve transgender AMAB individuals exhibited impaired semen parameters prior to GAHT initiation. Prior GAHT exposure showed a trend toward poorer semen quality. These findings support early fertility counseling and preservation in transgender individuals prior to GAHT initiation.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Genetic variability within the follicle-stimulating hormone (FSH)-related genes might contribute to phenotypic heterogeneity in patients with Klinefelter syndrome (KS), yet its clinical impact on sperm retrieval remains unclear.
To investigate the association between FSHB c.211 G > T and FSHR polymorphisms (c.2039 A > G and c.29 G > A) and hormonal parameters, as well as their potential role in predicting sperm retrieval rate (SRR) in patients with KS undergoing testicular sperm extraction (TESE).
A retrospective cohort of patients with KS was analyzed. Only subjects not receiving testosterone replacement therapy were included (n = 417). Hormonal, anthropometric, and clinical variables were compared across genotypes using nonparametric tests. Additive genetic models were applied to evaluate allele-dose effects. Multivariable logistic regression was performed to identify independent predictors of SRR. Predictive performance of clinical and combined clinical-genetic models was assessed using ROC curve analysis.
FSHB and FSHR genes polymorphisms were associated with variations in serum FSH concentrations, confirming a modulatory role of the FSH-related genes. In additive modeling, the FSHR c.29 G > A polymorphism emerged as an independent predictor of SRR (adjusted OR: 0.29; 95% CI, 0.09-0.97), whereas FSHB c.211 G > T showed a nonsignificant trend. The inclusion of genetic variants modestly improved predictive accuracy compared with clinical variables alone, as demonstrated by ROC analysis.
Genetic variants within the genes involved in FSH action might contribute incremental information for the prediction of sperm retrieval in patients with KS. While the overall predictive gain remains moderate, additive genetic modeling highlights a potential allele-dose effect of FSHR c.29 G > A on reproductive outcome, supporting a role for integrated clinical-genetic assessment in this population, although external validation remains required.
Klinefelter syndrome (KS) is characterized by marked phenotypic heterogeneity that might be influenced by genetic modifiers, including androgen receptor (AR) repeat length (CAGn and GGCn). The clinical relevance of these repeat lengths in patients with KS before testosterone replacement therapy (TRT) remains unclear.
To investigate the association between AR repeat length and anthropometric, hormonal, metabolic, and reproductive parameters in a well-characterized cohort of untreated adult patients with KS.
In this cross-sectional single-center study, 214 men with classical 47, XXY karyotype were evaluated prior to TRT. Clinical, biochemical, and reproductive parameters were analyzed according to AR CAGn and GGCn repeat length. Nonparametric tests, multivariable linear and logistic regression models, and interaction terms between CAGn and GGCn were tested. Standardized beta coefficients were used to compare the relative contribution of AR repeat length with major clinical determinants.
In unadjusted analyses, CAG repeat length was associated with estradiol concentrations, whereas GGC repeat length showed associations with hematocrit, platelet count, and total cholesterol. However, most associations were characterized by small effect sizes and did not persist after multivariable adjustment for possible confounders (age, BMI, and total testosterone levels). Moreover, AR repeat length was not associated with sperm retrieval rate. Standardized beta analyses demonstrated that testosterone levels, BMI, and age accounted for the largest proportion of phenotypic variability, whereas CAGn and GGCn repeat length had minimal roles.
In untreated patients with KS, AR repeat length (CAGn and GGCn) appears to have a limited clinical impact compared with classical endocrine and metabolic determinants. These findings suggest that phenotypic variability in KS might be primarily driven by chromosomal aneuploidy and primary testicular dysfunction rather than AR repeat length.
Graziani A et al., 2026·Journal of clinical medicine·Free full text on PubMed Central
Erectile dysfunction (ED) is increasingly recognized as an early manifestation of systemic vascular disease and might represent a window for cardiovascular risk assessment. Dynamic penile colour Doppler ultrasound (PCDU) provides quantitative arterial and venous parameters that could reflect subclinical vascular impairment. We investigated the association between PCDU parameters and estimated cardiovascular risk in men with ED. In this single-center retrospective observational study, 275 men undergoing PCDU for ED were evaluated. Clinical characteristics, biochemical data, and QRISK3 10-year cardiovascular risk scores were collected. Mean peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) were analyzed. Correlation analyses, logistic regression using a QRISK3 ≥ 10% threshold, linear regression models, age-stratified analyses, and receiver operating characteristic (ROC) curve analyses were performed. Patients with impaired PSV (<35 cm/s) were older and exhibited higher QRISK3 scores and a greater prevalence of diabetes mellitus and previous cardiovascular events. Mean PSV was inversely correlated with QRISK3 (r = -0.203, p < 0.01) and was associated with higher cardiovascular risk categories in unadjusted logistic regression (β = -0.016, p = 0.048), but not after adjustment for age and diabetes mellitus. ROC analysis showed modest discrimination of increased cardiovascular risk (AUC = 0.60). The addition of PSV to a model including age and diabetes resulted in minimal improvement in discrimination (AUC 0.966 vs. 0.968). Age-stratified analysis demonstrated a significant association between lower PSV and higher cardiovascular risk only in patients ≤60 years. A progressive increase in QRISK3 was observed according to the number of abnormal Doppler parameters (p = 0.013). PCDU parameters reflect the overall cardiovascular risk burden in men with ED. Although not independent predictors beyond traditional risk factors, penile Doppler abnormalities might identify a vascular phenotype associated with higher estimated cardiovascular risk, particularly in younger individuals. These findings support the role of comprehensive vascular assessment in selected patients with ED.
To investigate the rate of sperm DNA fragmentation in male partners of women with recurrent pregnancy loss and fertile control women.
Systematic review and meta-analysis.
Not applicable. PATIENT(S): A total of 579 male partners of women with recurrent pregnancy loss and 434 male partners fertile control women. INTERVENTION(S): Prospective studies were identified through a Pubmed search. Recurrent pregnancy loss was defined as two or more previous pregnancy losses. Fertile control women had a history of a live birth or ongoing pregnancy. MAIN OUTCOME MEASURE(S): The primary outcome was the rate of sperm DNA fragmentation. The summary measures were reported as mean difference with 95% confidence interval (CI). RESULT(S): Fifteen prospective studies were included in a qualitative review. Pooled data from 13 studies with sufficient data for meta-analysis suggest that male partners of women with a history of recurrent pregnancy loss have a significantly higher rate of sperm DNA fragmentation compared to the partners of fertile control women: mean difference 11.91, 95% CI 4.97-18.86. CONCLUSION(S): These findings support an association between sperm DNA fragmentation and recurrent pregnancy loss. However, given the significant heterogeneity between studies and lack of prospective pregnancy outcome data, further large prospective studies are needed.
Robinson L et al., 2012·Human reproduction (Oxford, England)
Is there an association between high levels of sperm DNA damage and miscarriage? Miscarriage rates are positively correlated with sperm DNA damage levels. Most ejaculates contain a subpopulation of sperm with DNA damage, also referred to as DNA fragmentation, in the form of double or single-strand breaks which have been induced in the DNA prior to or following ejaculation. This DNA damage may be particularly elevated in some subfertile men, hence several studies have examined the link between sperm DNA damage levels and conception and miscarriage rates. STUDY DESIGN, SIZE, A systematic review and meta-analysis of studies which examined the effect of sperm DNA damage on miscarriage rates was performed. Searches were conducted on MEDLINE, EMBASE and the Cochrane Library without any language restrictions from database inception to January 2012. PARTICIPANTS/MATERIALS, SETTING, We used the terms 'DNA damage' or 'DNA fragmentation' combined with 'miscarriage', 'abortion' or 'pregnancy' to generate a set of relevant citations. Data extraction was performed by two reviewers. Study quality was assessed using the Newcastle-Ottawa Scale. Meta-analysis of relative risks of miscarriage was performed with a random effects model. Subgroup analyses were performed by the type of DNA damage test, whether the sperm examined were prepared or from raw semen and for pregnancies resulting from IVF or ICSI treatment. MAIN We identified 16 cohort studies (2969 couples), 14 of which were prospective. Eight studies used acridine orange-based assays, six the TUNEL assay and two the COMET assay. Meta-analysis showed a significant increase in miscarriage in patients with high DNA damage compared with those with low DNA damage [risk ratio (RR) = 2.16 (1.54, 3.03), P < 0.00001)]. A subgroup analysis showed that the miscarriage association is strongest for the TUNEL assay (RR = 3.94 (2.45, 6.32), P < 0.00001). LIMITATIONS, There is some variation in study characteristics, including the use of different assays and different thresholds for DNA damage and the definition of pregnancy loss. The use of methods which select sperm without DNA damage for use in assisted conception treatment may reduce the risk of miscarriage. This finding indicates that assays detecting DNA damage could be considered in those suffering from recurrent pregnancy loss. Further research is necessary to study the mechanisms of DNA damage and the potential therapeutic effects of antioxidant therapy. STUDY FUNDING/COMPETING INTEREST(S): None.
Esteves SC et al., 2020·Andrologia·Free full text on PubMed Central
We herein summarise the evidence concerning the impact of sperm DNA fragmentation in various clinical infertility scenarios and the advances on sperm DNA fragmentation tests. The collected evidence was used to formulate 41 recommendations. Of these, 13 recommendations concern technical aspects of sperm DNA fragmentation testing, including pre-analytical information, clinical thresholds and interpretation of results. The remaining 28 recommendations relate to indications for sperm DNA fragmentation testing and clinical management. Clinical scenarios like varicocele, unexplained infertility, idiopathic infertility, recurrent pregnancy loss, intrauterine insemination, in vitro fertilisation/intracytoplasmic sperm injection, fertility counselling for men with infertility risk factors and sperm cryopreservation have been contemplated. The bulk evidence supporting the recommendations has increased in recent years, but it is still of moderate to low quality. This guideline provides clinicians with advice on best practices in sperm DNA fragmentation testing. Also, recommendations are provided on possible management strategies to overcome infertility related to sperm DNA fragmentation, based on the best available evidence. Lastly, we identified gaps in knowledge and opportunities for research and elaborated a list of recommendations to stimulate further investigation.
Mowla S et al., 2025·eLife·Free full text on PubMed Central
Several studies have associated seminal microbiota abnormalities with male infertility but have yielded differing results owing to their limited sizes or depths of analyses. The semen microbiota during recurrent pregnancy loss (RPL) has not been investigated. Comprehensively assessing the seminal microbiota in men with reproductive disorders could elucidate its potential role in clinical management. We used semen analysis, terminal-deoxynucleotidyl-transferase-mediated-deoxyuridine-triphosphate-nick-end-labelling, Comet DNA fragmentation, luminol reactive oxidative species (ROS) chemiluminescence, and metataxonomic profiling of semen microbiota by 16S rRNA amplicon sequencing in this prospective, cross-sectional study to investigate composition and bacterial load of seminal bacterial genera and species, semen parameters, ROS, and sperm DNA fragmentation in men with reproductive disorders and proven fathers. 223 men were enrolled, including healthy men with proven paternity (n=63), the male partners in a couple encountering RPL (n=46), men with male factor infertility (n=58), and the male partners of couples with unexplained infertility (n=56). Rates of high sperm DNA fragmentation, elevated ROS, and oligospermia were more prevalent in the study group compared with control. In all groups, semen microbiota clustered into three major genera-dominant groups (1, Streptococcus; 2, Prevotella; 3, Lactobacillus and Gardnerella); no species clusters were identified. Group 2 had the highest microbial richness (p<0.001), alpha-diversity (p<0.001), and bacterial load (p<0.0001). Overall bacterial composition or load has not been found to associate with semen analysis, ROS, or DNA fragmentation. Whilst global perturbation of the seminal microbiota is not associated with male reproductive disorders, men with unidentified seminal Flavobacterium are more likely to have abnormal seminal analysis. Future studies may elucidate if Flavobacterium reduction has therapeutic potential.
Male Fertility › Semen Analysis › Sperm Function Testing · Infertility › Recurrent Pregnancy Loss › Immune and Thrombophilia Factors
Annalisa Inversetti, Arianna Bossi, Martina Cristodoro, Alessandro Larcher, Andrea Busnelli, N Di Simone
A Inversetti, A Bossi, M Cristodoro, A Larcher, A Busnelli
PMID 37881014 37881014 DOI 10.1111/andr.13540 10.1111/andr.13540 Inversetti et al. 2025, Inversetti 2025
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