Juan, 36, is undergoing semen analysis to evaluate sperm quality after he and his partner were unable to conceive despite trying for some time. In his first sample, collected after several days of abstinence, he provides a larger volume. A second sample submitted a few days later has a lower volume and fewer sperm — and might initially appear to be of poorer quality. But recent research suggests that more semen volume does not necessarily mean better fertility potential, since longer periods of abstinence can increase volume without improving fertilizing capacity.

Until now, the standard recommendation before semen analysis or starting assisted reproductive technology (ART) has been to abstain from ejaculation for several days. The reasoning has been straightforward: The longer sperm are stored, the greater the ejaculate volume, concentration, and total sperm count tend to be. But a higher volume alone does not determine sample quality.

Several meta-analyses published in recent years have found that longer intervals without ejaculation are associated with greater sperm DNA fragmentation and poorer progressive motility. These findings are prompting a reevaluation of one of the most deeply held beliefs about male fertility: whether “storing” semen for a longer period actually improves sperm quality and the chances of conception.

A comprehensive study published in Proceedings of the Royal Society B in 2026 analyzed 115 studies involving 54,889 men, along with 56 studies in 30 species. The findings suggest that longer storage times are linked to increased oxidative stress and DNA damage, as well as lower sperm motility and viability. The researchers propose that, like other cells, sperm also age: After development is complete, they remain stored before ejaculation and can gradually deteriorate in a process they call post-meiotic sperm senescence.

2-7 Days of Abstinence

The World Health Organization (WHO) recommends a period of abstinence of 2-7 days before collecting a sample for semen analysis. However, the primary purpose of this recommendation is to standardize sample collection and facilitate the comparison of results between laboratories, not to determine which interval offers the best chance of achieving pregnancy.

A semen analysis requires relatively consistent conditions to accurately interpret parameters such as volume, concentration, and total sperm count. The WHO recommendation therefore allows for the comparison of results under standardized conditions, but this interval is designed to facilitate comparison between samples, not to indicate which interval is best for maximizing the chances of natural pregnancy or the outcomes of in vitro fertilization (IVF) or intracytoplasmic sperm injection. This difference between the best sample for semen analysis and the one that might be most suitable for achieving a pregnancy is one of the main points of debate.

More Sperm Isn’t Always Better

Semen is neither a uniform substance nor a simple reservoir of reproductive cells. In fertility testing, factors such as ejaculate volume, sperm concentration per mL, total count, motility, viability, and morphology are evaluated. All provide information, but none alone can determine a couple’s ability to achieve pregnancy.

Recent research has turned to a less visible but potentially more important variable: sperm DNA integrity. Sperm may be abundant, appear morphologically normal, and even demonstrate good motility, yet still carry damage or breaks in their genetic material.

In this regard, a meta-analysis published in Frontiers in Endocrinology in 2024, which included 13 studies and 2315 participants, revealed that longer periods of abstinence were associated not only with higher sperm concentration and greater seminal volume but also with an average increase of 3.46 points in sperm DNA fragmentation and lower progressive motility. Furthermore, the authors observed a relationship between the number of days of abstinence and an increase in both sperm concentration and the marker of genetic damage. 

Breaks and Damage to Genetic Material

Another review of 85 studies, published in the journal Andrology in 2024, reached a similar conclusion, noting that shorter periods of abstinence were associated with lower DNA fragmentation. In men with unexplained infertility, the observed average reduction in the DNA fragmentation index was 5.63 percentage points when comparing short intervals to longer ones.

A third study, published in the World Journal of Men’s Health in 2025 and based on 22 studies involving 31,640 samples, found a similar overall pattern: Shorter abstinence periods were linked to lower semen volume and sperm concentration but higher total and progressive motility and less DNA fragmentation. In both studies, sperm morphology did not differ significantly.

The results, however, should be interpreted with caution. The studies included fertile men, donors, patients at fertility clinics, and men with semen abnormalities; furthermore, not all studies used the same cutoff points or the same methods for measuring DNA fragmentation. Therefore, it is not yet possible to establish a universal optimal number of days of abstinence for all situations.

What Happens to Sperm During Abstinence?

The possible biological explanation for these results lies in storage time. After completing their development, mature sperm remain in the epididymis and other segments of the male reproductive tract until ejaculation. During this period, they may be exposed to reactive oxygen species, leading to membrane alterations and lipid peroxidation, causing them to accumulate damage over time.

The 2026 meta-analysis, led by the University of Oxford and the most comprehensive published to date on this topic, reinforces this hypothesis. By compiling data from more than 100 human studies and dozens of animal studies, the authors observed a general pattern of deterioration associated with storage and suggested that sperm aging could be a phenomenon shared by different species.

This finding does not mean that every day without ejaculation automatically reduces fertility in all men. The observed associations are general in nature, and the exact clinical consequences for each patient and treatment remain to be determined.

Is the Second Sample of Higher Quality?

One of the most striking lines of research examines what happens with the second sample collected shortly after the first. The data suggest that, although it typically contains less semen and fewer sperm, in certain men it may exhibit better quality parameters. A 2022 study, which analyzed 19 studies on a second ejaculation obtained after an interval of less than 4 hours, found that, in men with semen abnormalities, the second sample was associated with higher concentration and greater total and progressive motility, as well as a significant reduction in sperm DNA fragmentation.

The results were not consistent across all groups, but the study raised the possibility that, in certain men, a second ejaculation may yield fewer sperm, yet sperm that are potentially more functional and have less genetic damage. However, improving a semen parameter does not necessarily equate to increasing the chances of pregnancy. A sperm may exhibit lower DNA fragmentation or higher motility without this automatically translating into a clinically relevant improvement in fertilization.

However, a review published in the Journal of Clinical Medicine in 2023, which analyzed 24 studies on abstinence duration, DNA fragmentation, and reproductive outcomes, found that shorter intervals were associated with better pregnancy and live birth rates following ARTs, as well as lower DNA fragmentation. The heterogeneity of the studies, however, prevented the establishment of an ideal interval for all patients.

From the Semen Analysis to Pregnancy

Male fertility cannot be reduced to a single number. Sperm count is important, but it is only one step in a much more complex process: Sperm must travel, penetrate the barriers surrounding the egg, fertilize it, support early embryonic development, and ultimately lead to an embryo capable of implanting and continuing to develop. Human reproduction is also influenced by oocyte, embryonic, uterine, endocrine, genetic, and environmental factors.

Therefore, the decisive clinical outcomes are not concentration or DNA fragmentation alone, but rather fertilization, clinical pregnancy, miscarriage, and live birth. It is precisely in these outcomes where the evidence regarding the duration of abstinence remains less conclusive.

A study published in Reproductive Biomedicine Online in 2024 observed a relationship between each additional day of abstinence and a 3% reduction in the probability of obtaining zygotes with normal fertilization — so-called 2PN zygotes, with two pronuclei — along with an increase in abnormal 3PN fertilizations, with three pronuclei. However, the study did not find a statistically significant association with development to the blastocyst stage, cumulative pregnancy, or miscarriage.

The finding shows that changes can occur in the very early stages of fertilization without subsequently translating into detectable differences in pregnancy outcomes. It also reflects a common problem in reproductive medicine, given that intermediate outcomes are easier and faster to measure than live births but do not always reliably predict the outcome that matters most to couples.

A cohort of 541 couples undergoing IVF, published in F&S Reports in 2025, reached a similar conclusion. As the number of days of abstinence increased, semen volume, concentration, and total motile sperm count also increased. However, within the range of 2-7 days, the researchers found no differences in fertilization rates, clinical pregnancy, miscarriage, or live birth.

The literature on intrauterine insemination also does not offer a definitive answer. A trial published in the European Journal of Obstetrics & Gynecology and Reproductive Biology in 2025 compared different abstinence periods and found no statistically significant differences in the live birth rate. In that specific cohort, shortening the abstinence period did not result in an unequivocal clinical improvement.

The most rigorous conclusion is that the duration of abstinence clearly alters certain semen parameters. However, it has not yet been consistently demonstrated that changing the number of days without ejaculation affects the likelihood of having a child.

Upon arriving at the lab, Juan assumes that the more days he has gone without ejaculating, the better his sample will be, but recent research is forcing a reevaluation of that logic. The second sample may contain fewer sperm and yet still show better quality parameters in some men. Between the results of a semen analysis and the birth of a child, the evidence continues to leave questions unanswered, but one idea seems increasingly untenable: that, in male fertility, more days of abstinence necessarily mean better chances of conception.

This story was translated from El Médico Interactivo on Univadis, part of the Medscape Professional Network.