Semen Analysis and Sperm Facts

Males are the sole cause of infertility in about 20 percent of infertile couples and part of the cause in another 30-40 percent of cases, according to the American Society for Reproductive Medicine (ASRM). The primary source of male infertility is related to sperm, which is tested using a semen analysis.

A semen analysis is often a routine part of an initial evaluation for causes of infertility. This laboratory evaluation of a sample of the man’s semen can help fertility doctors analyze the cause of male infertility and its severity. Problems identified can sometimes be corrected, or can indicate that assisted reproductive technologies may be needed for a couple to achieve pregnancy.

Semen is the fluid ejaculated through the penis during a man’s sexual climax. It contains the sperm necessary to fertilize the woman’s egg for pregnancy, as well as other seminal fluids that help transport the sperm. The seminal fluids are produced by the prostate, sex glands and seminal vesicle glands, which are near the urethra and secrete many components of semen.

Sperm facts

Sperm development

Sperm development is called spermatogenesis. Although controlled by the body’s endocrine (hormonal) system, sperm development occurs in the ducts of the testes, with each production cycle consisting of six stages and requiring about 16 days.

Following development, sperm can swim to a female egg due to energy-generating parts of each cell called mitochondria, which power the sperm’s tail (flagellum) once inside the vagina.

Sperm are carried in semen, in which typical volume in an ejaculation ranges from 2 to 5 milliliters. That’s one-fourteenth to one-sixth of a fluid ounce.

Sperm count

Sperm count or concentration refers to the number of sperm cells per milliliter of semen. Men with 10 million or fewer sperm per milliliter are considered subfertile. The diagnosis of oligospermia means there is a very low sperm count. Approximately 15 million or higher is considered average; 40 million sperm or higher per milliliter suggests normal fertility.

Men diagnosed with azoospermia have no sperm in their semen. Often, there are no symptoms for this disorder, and men with this condition may even have a normal ejaculation process.

Men with acquired obstructive azoospermia have no sperm due to a vasectomy, a failed vasectomy reversal or an infection. They can also be unable to ejaculate due to spinal cord injury or psychological reasons. Fortunately, state-of-the-art reproductive technologies make it possible for these men to overcome their unique fertility challenges and have children.

Sperm motility and vitality

Sperm motility is graded by the number and quality of the sperm movement, ranging in decreasing order from rapid progressive, slow progressive, nonprogressive and immotile. Normal motility is when at least 60 percent of the sperm demonstrate rapid or slow progressive movement immediately after the sample liquefies and that movement is sustained for at least three hours.

Sperm vitality determines the number of living sperm in a sample. At least 50 percent of ejaculated sperm should be alive.

Sperm morphology

Sperm morphology is an assessment of the physical appearance of individual sperm, notably the head and tail characteristics. At least 4 percent of the sperm should be normal. If the male produces an adequate volume of sperm, the sperm’s morphology is most often the best predictor of male fertility.

Assessing the white blood cell count in semen is another aspect of an analysis. When the white blood cell count in the semen is too high, it can damage the sperm’s genetic material, as well as weaken the sperm. This condition is called pyospermia.

How a semen analysis works

Collecting semen

The patient provides a semen sample for laboratory analysis that he obtains by masturbation or by intercourse using a special condom that has no elements that can be toxic to the sperm. If masturbating to obtain semen, the man can do that at home or, preferably, at the fertility clinic. When masturbating, the patient should not use any lubricants, particularly water-based ones, as lubricants can affect the semen.

If the man will be gathering the semen at home, the fertility staff will instruct him on how to store the sample. He must bring it to the lab or fertility clinic within one hour of obtaining the sample.

Additionally, the patient must abstain from ejaculating for 2-5 days prior to obtaining the sample. Some men with severe oligospermia may not need to abstain for that length of time.

Evaluating the semen sample

Laboratories adhere to strict guidelines in evaluating the semen sample and reporting the findings, most often using the Kruger method of assessing sperm morphology. The semen analysis can suggest that a man is infertile due to lack of healthy sperm or inadequate volume.

The semen analysis helps fertility doctors evaluate couples that have not gotten pregnant from in vitro fertilization (IVF). It can also indicate which couples might benefit from intracytoplasmic sperm injection (ICSI) to help sperm with identified problems better penetrate the outer covering of the woman’s egg called the zona pellucida.

Because sperm production in the same male can vary considerably from day to day, it’s a good idea to conduct a secondary semen analysis if the first shows considerable abnormalities. If this second analysis corroborates what the first one found, the fertility physician will begin a discussion with the patient on treatment options to correct or bypass the problems.

Some men first may be referred for a urologic evaluation. The reproductive endocrinologist may also recommend genetic and hormonal testing.

Other types of semen analysis

In addition to the findings on sperm health described above, a semen analysis can also evaluate other issues.

Other sperm analyses can include an assessment of sperm DNA fragmentation. If one of the two strands of DNA are damaged, it can scramble genetic information the embryo needs to grow, resulting in male infertility.

Certain antibodies can develop in the blood or semen (also in vaginal fluids) and affect the sperm’s ability to move and fertilize the female egg. Thus, antisperm antibody testing may be conducted in a semen analysis to evaluate the sperm for this condition.