OBJECTIVE--To investigate whether semen quality has changed during the past 50 years. DESIGN--Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991). SUBJECTS--14,947 men included in a total of 61 papers published between 1938 and 1991. MAIN OUTCOME MEASURES--Mean sperm density and mean seminal volume. RESULTS--Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density. CONCLUSIONS--There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.

https://www.bmj.com/content/bmj/305/6854/609.full.pdf

Evidence for decreasing quality of semen during past 50 years.

BACKGROUND Semen quality is taken as a surrogate measure of male fecundity in clinical andrology, male fertility, reproductive toxicology, epidemiology and pregnancy risk assessments. Reference intervals for values of semen parameters from a fertile population could provide data from which prognosis of fertility or diagnosis of infertility can be extrapolated. METHODS Semen samples from over 4500 men in 14 countries on four continents were obtained from retrospective and prospective analyses on fertile men, men of unknown fertility status and men selected as normozoospermic. Men whose partners had a time-to-pregnancy (TTP) of < or =12 months were chosen as individuals to provide reference distributions for semen parameters. Distributions were also generated for a population assumed to represent the general population. RESULTS The following one-sided lower reference limits, the fifth centiles (with 95th percent confidence intervals), were generated from men whose partners had TTP < or = 12 months: semen volume, 1.5 ml (1.4-1.7); total sperm number, 39 million per ejaculate (33-46); sperm concentration, 15 million per ml (12-16); vitality, 58% live (55-63); progressive motility, 32% (31-34); total (progressive + non-progressive) motility, 40% (38-42); morphologically normal forms, 4.0% (3.0-4.0). Semen quality of the reference population was superior to that of the men from the general population and normozoospermic men. CONCLUSIONS The data represent sound reference distributions of semen characteristics of fertile men in a number of countries. They provide an appropriate tool in conjunction with clinical data to evaluate a patient's semen quality and prospects for fertility.

/pdf/world-health-organization-reference-values-for-human-semen-3qu21s6tqf.pdf

World Health Organization reference values for human semen characteristics

WHO laboratory manual for the examination and processing of human semen

Endometriosis

https://www.obgyn.theclinics.com/article/S0889-8545(05)70302-8/pdf

Epidemiology of endometriosis

This study aimed to determine the number and distribution of spermatozoa within the human Fallopian tubes around ovulation. Parous women, undergoing total abdominal hysterectomy for menorrhagia, were inseminated with either partner's semen (3/10) or donor semen (7/10). Approximately 18 h later both Fallopian tubes were ligatured into ampullary, isthmic and intramural regions. These were removed and assessed for sperm content by flushing, scanning electron microscopy (SEM) or homogenization. A median of 251 spermatozoa were recovered (range, 79-1386). The number of spermatozoa within each tube was not significantly different. The ovulatory ampulla contained a significantly (P < or = 0.01) larger percentage of spermatozoa than the non-ovulatory ampulla. The number of motile spermatozoa inseminated was not significantly correlated to the number of spermatozoa recovered, but a trend was identified. The time between the onset of the luteinizing hormone surge and hysterectomy was significantly correlated (P < or = 0.01) to the number of spermatozoa within the intramural regions, but not to the tubal sperm distribution. Spermatozoa were not observed, by SEM, bound to the tubal epithelium. These data suggest that, after artificial insemination at least, sperm access to the human Fallopian tube may be controlled, but that ovulation does not affect the redistribution of spermatozoa between tubal regions and that the isthmus does not appear to act specifically as a sperm reservoir.

Sperm numbers and distribution within the human fallopian tube around ovulation

Intra- and inter-technician variability in assessing sperm motility by the methods recently advocated by the World Health Organization (WHO) were studied. The intra- and inter-technician variability in estimating sperm concentration and the intra-technician variability in assessing sperm morphology were also examined. Intra-technician variability in assessing sperm motility appeared to be related to the natural ability and/or training of the observer. Although in general the intra-technician variability was low, there were marked and clinically significant differences between observers when assessing the same semen sample. There was no significant difference between observers in the assessment of sperm concentration, and intra-technician variability was low. When assessing sperm morphology, the intra-technician variability was potentially large (above a level of 20% morphologically ideal spermatozoa). Technicians should be recruited who have natural ability as observers. Quality control appears to be an essential exercise for any center that plans to relate semen parameters to fertility outcome.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1939-4640.1989.tb00124.x

Quality control during the conventional analysis of semen, an essential exercise.

The clinical value of conventional semen analysis

The usefulness of the hypo-osmotic swelling (HOS) test and the sperm mucus penetration (SMP) test as sperm function tests for in-vitro fertilization was analysed in 56 couples. Using logistic regression analysis only the SMP test was independently related to fertilization (P = 0.004), no false negative results were obtained, i.e. no fertilization if sperm from the ejaculate failed to penetrate mucus. The HOS test was of no predictive value. The results justify a further examination of the SMP test in other IVF centres.

The hypo-osmotic swelling test and the sperm mucus penetration test in determining fertilization of the human oocyte.

The clinical significance of antisperm antibodies for fertility remains controversial. In this study, we determined whether the presence, isotype, region and/or amount of sperm-bound antibody was of any predictive value for future fertility in 534 men using Cox's proportional hazards model. Significant correlations between the presence of antibodies and semen parameters were recorded, such as sperm mucus penetration and sperm motility. However, low (less than 10%) negative binding and moderate (less than 50%) binding had no significant effect on the probability of conception or the time to conception. This study confirms in-vitro data suggesting that sperm function is not impaired unless the degree of antibody binding to spermatozoa is very high.

B.C. Dunphy

Papers

Sperm numbers and distribution within the human fallopian tube around ovulation

Quality control during the conventional analysis of semen, an essential exercise.

The clinical value of conventional semen analysis

The hypo-osmotic swelling test and the sperm mucus penetration test in determining fertilization of the human oocyte.

The poor prognostic value of low to moderate levels of sperm surface-bound antibodies