Male factors can and do contribute to miscarriage, though the connection has been underappreciated for decades. Research increasingly shows that sperm quality, paternal age, chromosomal errors originating in the sperm, and even the composition of seminal fluid play roles in whether a pregnancy survives its earliest weeks. The medical establishment has historically focused almost entirely on maternal causes when evaluating pregnancy loss, but a growing body of evidence points to the father’s biology as a meaningful piece of the puzzle.
Sperm DNA Damage Is the Strongest Male-Side Link
The most studied male factor in miscarriage is something called sperm DNA fragmentation, which refers to breaks or damage in the genetic material packed inside sperm. A meta-analysis pooling data from 13 studies found that male partners of women with recurrent pregnancy loss had significantly higher levels of sperm DNA fragmentation compared to partners of women with no history of loss.1PubMed. Sperm DNA fragmentation and recurrent pregnancy loss: a systematic review and meta-analysis The difference was not subtle. In a large multicenter study, the group of men whose partners had recurrent losses had a median fragmentation index around 50% higher than that of men whose partners conceived without difficulty.2PubMed. Sperm DNA fragmentation and idiopathic recurrent pregnancy loss: Results from a multicenter case-control study
What makes this relevant to miscarriage specifically, rather than just infertility in general, is that sperm with fragmented DNA can still fertilize an egg. The embryo may begin developing, implant in the uterus, and even produce a positive pregnancy test. But the damaged genetic material can cause the embryo to stall, develop abnormally, or fail to progress past the first trimester. An egg has some capacity to repair DNA damage it receives from the sperm, but this repair system has limits. When the damage exceeds what the egg can fix, the pregnancy is more likely to fail.
One major driver of sperm DNA damage is oxidative stress, an imbalance between harmful reactive molecules and the body’s ability to neutralize them. Reactive oxygen species are produced naturally during sperm metabolism and actually serve useful functions at low levels, but in excess they attack the DNA inside sperm cells.3PubMed Central. The Role of Seminal Oxidative Stress in Recurrent Pregnancy Loss Smoking, alcohol, obesity, heat exposure, pollution, and certain infections all increase oxidative stress in the reproductive tract.4PubMed Central. Role of Oxidative Stress in Male Infertility: An Updated Review
How Paternal Age Raises the Risk
Just as maternal age is a well-known risk factor for miscarriage, paternal age independently raises the odds. A systematic review and meta-analysis covering multiple large studies found that men aged 40 to 44 had about a 23% higher risk of their partner miscarrying compared to men in their late twenties, and men 45 and older faced roughly a 43% increased risk.5PubMed Central. Advanced paternal age is associated with an increased risk of spontaneous miscarriage: a systematic review and meta-analysis When the analysis was restricted to first-trimester losses, the risk for men over 45 was even steeper, about 74% higher than the reference group.5PubMed Central. Advanced paternal age is associated with an increased risk of spontaneous miscarriage: a systematic review and meta-analysis
The reason is straightforward in broad terms. Unlike eggs, which a woman is born with, sperm are produced continuously throughout a man’s life. Each round of cell division is an opportunity for errors to creep in. As men age, their sperm accumulate more DNA mutations, more chromosomal abnormalities, and more epigenetic changes. The cumulative effect is that older sperm are, on average, more likely to produce embryos that cannot develop normally. Advanced paternal age is also specifically linked to recurrent pregnancy loss, not just isolated miscarriages.6PubMed Central. The paternal role in pregnancy loss
This does not mean that men over 40 will inevitably experience pregnancy loss. The absolute risk increase is modest for any individual couple. But at a population level, paternal age is a genuine and measurable contributor, and one that gets far less public attention than maternal age.
Chromosomal Errors in Sperm
Some men carry structural rearrangements in their chromosomes, most commonly what are called balanced translocations. A man with a balanced translocation has all his genetic material present, just rearranged, so he’s typically healthy himself. But when his cells divide to produce sperm, the rearrangement can result in sperm that carry too much or too little genetic material. Embryos formed from these unbalanced sperm are often not viable. Parental chromosome rearrangements are one of the most established causes of recurrent pregnancy loss, and the rates of loss are higher in carriers compared with couples who have normal karyotypes.7PubMed Central. Expectant management and live birth outcomes for male balanced-translocation carriers
Even without a known translocation, some men produce sperm with elevated rates of aneuploidy, meaning individual sperm carry the wrong number of chromosomes. One study found significantly elevated sperm aneuploidy in about 10% of men with a history of recurrent pregnancy loss, with affected men showing aneuploidy rates of 30 to 34%.8PubMed. Sperm aneuploidy and recurrent pregnancy loss Chromosomally abnormal sperm that fertilize an egg produce chromosomally abnormal embryos, and most chromosomally abnormal embryos miscarry. Research using genetic screening of embryos has confirmed that abnormal sperm chromosome results are associated with embryo aneuploidy, strengthening the link between sperm genetics and early pregnancy failure.9Biology of Reproduction. Sperm chromosomal abnormalities and their contribution to human embryo aneuploidy
The Immune Priming Role of Seminal Plasma
One of the more surprising avenues of research involves not the sperm itself but the fluid it travels in. Seminal plasma, the liquid portion of semen, contains signaling molecules that interact with the lining of the female reproductive tract and modulate the maternal immune system. Because an embryo is genetically half-foreign to the mother’s body, the immune system needs to be “trained” to tolerate it rather than attack it. Seminal plasma appears to help start this process even before conception, priming immune cells in the uterus to accept a pregnancy.10PubMed. The seed to success: The role of seminal plasma in pregnancy
When this immune priming fails, the consequences may include pregnancy loss. A study comparing seminal plasma from male partners of women with unexplained recurrent losses to that of control men found measurable differences in immune function. Female immune cells exposed to seminal plasma from the loss group showed weaker suppressive responses and a more activated inflammatory profile. The seminal plasma from these men contained lower levels of key immune-regulating molecules, particularly TGF-β and VEGF.11PubMed. Impaired immunomodulatory effects of seminal plasma may play a role in unexplained recurrent pregnancy loss: Results of an in vitro study In plain terms, the semen of some men may not adequately prepare the mother’s immune system for pregnancy, and that failure of preparation may contribute to miscarriage.
Lifestyle, Toxins, and Infections
Paternal health is not just about genetics. A review of the evidence found that cardiovascular disease, metabolic syndrome, and general poor health in the father were each associated with higher risks of pregnancy loss.12PubMed. Effect of paternal health on pregnancy loss-A review of current evidence These conditions often go hand-in-hand with oxidative stress, inflammation, and hormonal imbalances, all of which can degrade sperm quality in the ways described above.
Environmental exposures add another layer. Research on agricultural workers has found increased miscarriage rates among wives of men exposed to certain pesticide classes.13PubMed. Male pesticide exposure and pregnancy outcome Broader population studies in areas with high pesticide use have reported elevated rates of miscarriage compared to regions with lower use.14PubMed. Association of reproductive disorders and male congenital anomalies with environmental exposure to endocrine active pesticides Chronic occupational exposure to various toxic substances has also been linked to increased miscarriage among partners.15PubMed. Teratogens and the male. An analysis with special reference to herbicide exposure The mechanism likely involves direct damage to sperm DNA and disruption of reproductive hormones.
Infections in the male reproductive tract are another potential contributor. Bacterial, viral, and other infections in the urogenital system can often be asymptomatic while still causing problems. These infections increase white blood cell counts in semen, drive up oxidative stress, and may even be transmitted to the partner. Male genital tract infections have been linked to fertilization failure, pregnancy loss, and developmental problems in offspring.16PubMed. Role of Infection and Leukocytes in Male Infertility
Paternal Medications Around Conception
An often-overlooked factor is what medications the father is taking when conception occurs. A large study examining nearly 1.4 million pregnancies found that a significant share of fathers were filling prescriptions around the time of conception. The most common drug classes were psychotropic medications (filled by about 9% of fathers), antibiotics (about 7%), and analgesics (about 7%).17PubMed Central. Patterns of Paternal Medication Dispensation Around the Time of Conception A small number of fathers were filling prescriptions for drugs known to cause birth defects when taken by the mother, including methotrexate and isotretinoin. Whether these same drugs cause harm when only the father takes them is less well established, but the finding highlights how rarely paternal medication use is considered in prenatal counseling.
The broader point is that sperm take about two to three months to develop. Medications, illnesses, and exposures during that developmental window can potentially affect the quality of sperm that eventually fertilize an egg. This is a meaningful blind spot in how most couples and clinicians approach pregnancy planning.
Why Male Partners Are Rarely Tested
Despite the accumulating evidence, the workup for recurrent pregnancy loss remains overwhelmingly focused on the woman. Standard clinical guidelines typically include only one test directed at the male partner: a karyotype analysis to check for chromosomal rearrangements like balanced translocations.18PubMed Central. The male contribution to recurrent pregnancy loss Sperm DNA fragmentation testing, despite growing evidence linking it to recurrent loss, is not part of the routine evaluation in most clinical settings.18PubMed Central. The male contribution to recurrent pregnancy loss
Some researchers have argued that this gap needs to close. A narrative review of male factor testing in recurrent pregnancy loss concluded that semen analysis should be standard for men in affected couples, and that DNA fragmentation testing and sperm aneuploidy assessment could be valuable additions to the clinical toolkit.19PubMed Central. Male factor testing in recurrent pregnancy loss cases: A narrative review Professional organizations have begun acknowledging the male as a possible risk factor, but specific diagnostic and therapeutic recommendations are still lacking, and management remains largely case by case.20PubMed Central. Recurrent miscarriage and male factor infertility: diagnostic and therapeutic implications. A narrative review.
For couples experiencing repeated losses, this means it can be worth raising the question proactively. A standard semen analysis can flag obvious problems with sperm count, motility, and shape, but it will not catch DNA fragmentation or chromosomal issues. Specialized testing exists and is available at fertility clinics, even if it is not yet on the standard checklist.
Can Antioxidants or Other Treatments Help?
Given that oxidative stress is a major driver of sperm DNA damage, antioxidant supplements are a natural area of interest. The research here is underwhelming so far. A Cochrane systematic review of antioxidant supplementation for subfertile men found no clear evidence that antioxidants reduced miscarriage rates. Only six trials reported miscarriage as an outcome, and the event rates were too low to draw firm conclusions, with the evidence rated as very low certainty.21Cochrane Database of Systematic Reviews. Antioxidants for male subfertility One randomized trial of antioxidant pretreatment before assisted reproduction actually reported numerically more miscarriages in the antioxidant group than the control group, though the numbers were small and not designed to test that outcome specifically.22Human Reproduction Open. Antioxidant pretreatment for male partner before ART for male factor subfertility: a randomized controlled trial
This does not mean lifestyle changes are useless. Quitting smoking, reducing alcohol, losing weight, managing chronic health conditions, and avoiding unnecessary heat exposure to the testes are all known to improve sperm quality markers. Whether these improvements translate directly into fewer miscarriages has not been proven in controlled trials, but the biological rationale is solid. For men with known chromosomal translocations, preimplantation genetic testing during IVF can screen embryos for unbalanced arrangements before transfer, which does reduce miscarriage rates in that specific population.
Epigenetic Cargo in Sperm
Beyond the DNA sequence itself, sperm carry an epigenetic cargo, a set of chemical marks and small RNA molecules that influence how the embryo’s genes are activated in its earliest hours of development. This is a newer and more complex area of research, mostly conducted in animal models, but the findings are striking.
Mouse studies have shown that disrupting certain chemical marks on sperm DNA can cause severe developmental defects in offspring, and these effects can persist for multiple generations even when the offspring themselves do not carry the original genetic alteration.23Nature Communications. Emerging evidence that the mammalian sperm epigenome serves as a template for embryo development Other research has found that small RNA molecules carried by sperm are essential for normal gene regulation in early embryos, and that injecting the right set of small RNAs can rescue embryos that would otherwise develop abnormally.24Developmental Cell. Small RNAs Are Trafficked from the Epididymis to Developing Mammalian Sperm Paternal small RNAs appear to play a role in controlling gene expression through fertilization and the first several cell divisions.25Development. Sperm-borne miRNAs and endo-siRNAs are important for fertilization and preimplantation embryonic development
Translating these findings directly to human miscarriage is premature. But they establish that sperm contribute far more to early embryo development than just a set of chromosomes. If the epigenetic programming in sperm is altered by age, environment, diet, or disease, it could plausibly disrupt the earliest and most vulnerable stages of pregnancy. This is an area where the science is developing fast, and clinical applications may follow in the coming years.
The Seminal Microbiome
A recent and unexpected line of inquiry involves the bacteria that live in semen. A prospective study published in The Lancet examined the gut, vaginal, and seminal microbiomes of couples undergoing fertility treatment and those with recurrent pregnancy loss. The researchers identified a pattern they called “seminal V-dysbiosis,” where the bacterial community in a man’s semen resembled the type of vaginal microbiome associated with poor reproductive outcomes. Men with this pattern saw their partners experience significantly higher rates of pregnancy loss. In the IVF group, roughly 85% of couples without seminal dysbiosis achieved a live birth, compared to only 57% of couples where it was present.26The Lancet. Gut, vaginal, and seminal microbiomes and reproductive outcomes in couples with infertility and recurrent pregnancy loss: a prospective multicentre cohort study The association also held in the recurrent pregnancy loss group.
This is early-stage research with a single study, so the findings need replication. But the idea that the bacterial composition of semen could influence pregnancy outcomes adds yet another mechanism through which the male partner’s biology may matter. It also raises the possibility that some cases of “unexplained” recurrent loss might eventually be traceable to microbial factors no one was previously testing for.
Genomic Imprinting and Parental Conflict
There is a deeper evolutionary dimension to the father’s genetic contribution that is sometimes overlooked. In mammals, certain genes are “imprinted,” meaning they are active only when inherited from one parent and silenced when inherited from the other. Paternally imprinted genes tend to promote aggressive growth of the placenta and embryo, while maternally imprinted genes tend to restrain that growth. This sets up a kind of tug-of-war within the developing embryo, with the father’s genes pushing for maximum resource extraction from the mother and the mother’s genes moderating the demand.27Wiley Online Library / American Journal of Reproductive Immunology. Altercation of generations: genetic conflicts of pregnancy
When imprinting goes wrong, the consequences can be severe. Errors in paternal imprinting are implicated in conditions like complete hydatidiform mole, where an embryo with only paternal genetic material produces a mass of placental tissue but no viable fetus. While this is an extreme case, subtler imprinting errors could contribute to less dramatic forms of pregnancy failure. The concept underlines something fundamental: the father’s genetic and epigenetic contribution is not a passive ingredient. It actively shapes whether and how a pregnancy develops, starting from the very first cell divisions.