This Cyberounds® is on male fertility/infertility. A second Cyberounds® will cover female fertility/infertility. In both, I hope to refresh your knowledge about the essential elements of successful human reproduction and bring you up to date about the rapidly evolving field of assisted reproductive technology (ART).

Currently, in Western countries, about 10-15% of couples experience some difficulty with fertility.(1) Remedies range from a visit to a primary physician, providing education and adjustments in timing attempts to conceive, to placing the entire reproductive process under specialty control. The causes of infertility may vary, depending on the population examined. Are you looking at everyone with a fertility problem or are you looking at those who consult specialized facilities?

Fertility problems are usually ascribed as caused by 30-40% male factor, 30-40% female factor with the remainder said to be either some combination of factors from both members of the couple or not identifiable by any current method. The Centers for Disease Control collects data from fertility clinics on the special population of patients using in vitro fertilization technology. Their data is given on treatment cycles, rather than patients. Their latest figures in women under 35 categorized causes as 40% female, 23% male, 17% combined male and female factors, 10% more than one female factor and 10% unexplained by any definable cause.(2) By both these compilations, male factor infertility is operative in 40% of couples.

What is Infertility, Subfertility, Sterility?

Different words are used to define different situations. Definitions have changed, as technology has changed.

Sterility is the absolute inability to procreate: an absent uterus in women, absent testes in men. In years past, a woman with blocked fallopian tubes or a man with an obstructed vas deferens would be sterile. But with assisted reproductive technology (ART), this is no longer the case.

Infertility is usually defined as no pregnancy after one year of frequent unprotected intercourse. This is a relative measurement. Over time many couples may achieve pregnancy. In five years, nearly one half of "infertile" couples will conceive.

Subfertility is used to describe gradations between normal fertility and sterility, usually interchangeably with infertility.

Fecundability is the pregnancy rate from one menstrual cycle. The normal rate in humans is 20%. Seventy-five percent of normally fertile couples are expected to have conceived in six months, and almost 100% by one year.(1)

Normal fertility can be considered from several different points of view: the couple, the female and the male. In this Cyberounds^®, we are going to look at male fertility: the biological steps and mechanisms, the defects, the causes of the defects and what to do.

Normal Male Fertility

As male factors have been increasingly identified as a cause of infertility, investigators have been focusing on the underlying processes. Yes the sperm count is low, but why? Or, the sperm parameters are normal, but the sperm cannot fertilize.

When you look at the male contribution to the procreative process, you realize that there are dozens of steps that go into creating a completely normal spermatozoon, whether you are talking about the structure of the testis, the hormones that influence its function, the receptors for the hormones, the maturation process from the germ cell, the composition of the seminal plasma, and all the enzymes, receptors, and reactions that make the sperm capable of fertilizing the egg. There are dozens of opportunities for mistakes. First, let's look at what goes into normal male fertility.

Role of the Pituitary

The testis has two main parts. The interstitial portion contains the Leydig cells, which produce testosterone and are sensitive to luteinizing hormone (LH). The other functional component is the seminiferous tubules, which contain the Sertoli cells and the germ cells, and are influenced by follicle stimulating hormone (FSH) and testosterone. The two pituitary hormones, LH and FSH, are named for their function in females because they were first identified in females. Later they were found to be equally important in male reproduction. These pituitary hormones are secreted in response to gonadotropin releasing hormone (GnRH), a 10-amino acid peptide secreted from nerve cells in the hypothalamus. GnRH goes directly to the pituitary through the pituitary portal circulation in pulses, ranging from once an hour or 1-2 times in 24 hours. There is a negative feedback loop by which GnRH, and, derivatively, LH and FSH, is "turned off" by testosterone. FSH is also turned off by inhibin, which is secreted by the Sertoli cell.

It is important to remember that GnRH is secreted in pulses, because if it is administered in a steady dose, as with leuprolide acetate (Lupron^® or Zoladex), the pituitary will stop secreting LH and FSH and testosterone levels will decrease and spermatogenesis will stop. A second important point is that excessive, non-physiologic exogenous testosterone, given for replacement, bodybuilding, or other purposes, can inhibit GnRH and sperm production.

Finally, the pituitary hormone prolactin (PL) can sensitize the LH receptors on the Leydig cells that produce testosterone. Prolactin also affects the function of both the prostate gland and the seminal vesicles. Elevated PL, such as caused by a pituitary adenoma, can interfere with GnRH function.

Testicular Function

Ninety percent of testicular volume is taken up by the seminiferous tubules where sperm are generated. The germ stem cells, the spermatogonia, are on the basement membrane of the tubule. These cells divide by mitosis and provide germ cells throughout the male lifespan. Each spermatogonium that starts the differentiation pathway divides by mitosis and then meiosis to produce four spermatozoa.

As the cells develop, they migrate toward the lumen. They go through six distinct stages, from spermatogonia to spermatocytes, to spermatids (which are haploid) and finally spermatozoa, which are released into the lumen. As the spermatid matures, it is surrounded by a Sertoli cell, often called a "nurse" cell. In this milieu, the sperm develops its characteristic features -- the head, the midpiece and the tail. The acrosome is formed on the head, the nucleus compacted to 10% of its original volume and almost all the cytoplasm is removed. The whole process from spermatogonium to spermatozoa, or sperm, takes about 74 days. As the sperm exit the seminiferous tubules, they have minimal motility and cannot fertilize an egg on their own.

The spermatozoa then move to the epididymis, the long, tightly packed convoluted tubule that is palpable posterolateral to the testis. As the sperm traverse the epididymis, further maturation takes place over another 10-15 days. So from germ cell to active spermatozoon, there is about a 90-day development period. That means that if spermatogenesis were entirely stopped at the germ cell level, the actual effect on sperm count would not be fully operational for three months. Conversely, recovery from such an insult may not be detected for three months after spermatogenesis resumed.

Semen Production

The secretions containing sperm that exit the epididymis only make up about 10% of the volume of the semen. These sperm are transported within the vas deferens, which courses within the spermatic cord in the inguinal canal, then separates to enter the pelvis, loops over the ureter, extending inferiorly, posterior to the bladder ending in the dilated ampullae. Each vas joins the duct from the seminal vesicle to form the ejaculatory duct, which enters the urethra distal to the bladder neck and traverses the prostate.

The seminal vesicles contribute about 70% of the volume of semen. The secretions are alkaline, rich in fructose and contain coagulating factors. The prostate, located between the membranous urethra and the bladder neck, contributes about 20% of semen volume. The secretions are acidic and contain proteolytic enzymes.

During ejaculation, the bladder neck closes and secretions from the vas, the seminal vesicles and the prostate are propelled through the urethra. "Retrograde ejaculation" occurs when the bladder neck does not close and the secretions are propelled into the bladder. Urinalysis will show copious sperm in the urine.

Fertilization

Once sperm are deposited in the vagina, they must traverse the cervical mucus, swim through the uterus and enter into the fallopian tubes. During this passage, the sperm undergoes capacitation, a series of changes and reactions that attract the sperm to the egg and make it capable of penetrating the cumulus oophorus, the layer of granulosa cells around the egg, and the zona pellucida, the thick mucopolysaccharide coat around the egg. Part of this process is the acrosome reaction, during which the cap over the head of the sperm dissolves, exposing hydrolytic enzymes that aid in penetrating the layers around the egg.

The sperm should be in the fimbriated portion of the fallopian tube when ovulation occurs because the egg will deteriorate quickly after it reaches the opening of the fallopian tube. As the sperm is attracted to the egg and makes contact, sperm motility becomes much more vigorous. When the sperm penetrates the zona pellucida, it fuses with the egg cell membrane and enters the cytoplasm. The "zona reaction" is the release of substances just below the cell membrane that prevent penetration by another sperm.

As mentioned above, there is a complex series of steps and reactions that takes place in the sperm to allow it to reach and penetrate the egg. Any one of these reactions can be defective. The more numerous the sperm, the better the motility, and the more that appear normal, the better the chance that fertilization will take place.

Defects in Male Fertility: First Step: Semen Analysis

In most cases, when a couple is having trouble conceiving, they will consult their generalist or the woman's gynecologist for a preliminary evaluation. The man would have a semen analysis. One caveat is that it should be done at a facility that has the technical expertise and depth of experience to do a reliable test. For an optimal specimen, the man is advised to abstain from ejaculation for 2-3 days. The sample is preferably produced by manual stimulation and given to the laboratory personnel immediately if produced at the facility or within 30-60 minutes from the time of ejaculation if obtained at home or other place. The sample is allowed to liquefy and is examined for volume, pH, sperm concentration, motility and morphology, and other characteristics.

The World Health Organization (WHO) cut-off criteria for normal semen parameters are volume 1.5-5.5ml, pH 7.2-7.8, concentration >20 x 10⁶ /ml, motility >50% and normal morphology >30%. Many andrology labs now use stricter Kruger criteria for morphology, in which a smaller percentage would be judged normal, 14% being the cut-off.

Investigators trying to standardize semen parameters have found that there is tremendous overlap between sperm count, motility and morphology in men with normal fertility and those with subfertility. A comparison of normally fertile and subfertile men showed a significant range of values, classified as indeterminate fertility, between the values definitively in the fertile population and those definitively in the subfertile population. Their values for the unequivocally fertile were concentration >48 x 10⁶ /ml, normal motility >63%, normal morphology >12%: their cut-off for impaired fertility was concentration <13.5 x 10⁶/ml, normal motility <32%, and normal morphology by strict criteria <9%.(3) See Table 1. Men with morphology in the infertile range had the highest risk for being infertile.

Diagnostic Terms Related to Semen Analysis

Different terms are used to describe semen characteristics:

• Azoospermia: no sperm in semen
• Oligospermia: <20 x 10⁶/ml (WHO)
• Severe oligospermia <5 x 10⁶/ml
• Asthenospermia: poor motility of sperm
• Teratospermia: abnormal forms <30% (WHO), <14% (Kruger)

Other Characteristics of and Elements in Semen

Volume and pH

Ten percent of semen volume is secretion from the testis. The seminal vesicle contribution to the semen is alkaline and 70% of the total; the prostate contribution is acidic and 20% of the total. If the semen is of small volume and acidic, there is no contribution from the seminal vesicles, which may be absent or blocked. If there is no sperm as well, the ejaculatory ducts could be absent or blocked as well. If the pH and volume are normal, but there are no sperm, there is either a physical blockage in the vas/epididymis or the testis sperm production is severely diminished or absent.

Round Cells

These cells could be leukocytes, immature forms of sperm and exfoliated epithelial cells. They can be distinguished by special staining. There should be fewer than one million leukocytes/ml and five million total round cells/ml in a specimen. Excess leukocytes could indicate active infection or inflammation. Large numbers of immature sperm forms may indicate defective maturation.

One potential cause of infertility that is receiving more research attention is the presence of reactive oxygen species (ROS) in the semen. Although normal amounts of these substances are mediators of normal sperm function, in excess, they damage sperm and can impair fertility. There is a delicate balance between antioxidants in the seminal plasma and the ROS. Both leukocytes and immature sperm forms can increase ROS and upset that balance.(5),(7)

Antisperm Antibodies

Sperm cells are isolated from the rest of the male body by the tight junctions of the Sertoli cells in the seminiferous tubules, the blood-testis barrier. If the barrier is breeched, antisperm antibodies can develop. Two tests used to detect these antibodies in a semen specimen are the immunobead test (IBT) and the mixed antiglobulin reaction (MAR) test. The tests are positive if there is a greater than 50% antibody coating of the motile sperm. The antibodies cause sperm to clump together and this can affect sperm motility. How much of a causative factor antibodies represent is hard to calculate, since some normally fertile men also have antisperm antibodies.(5)

Semen Analysis and Fertility

In a large series of new couples seeking help with infertility, about 25% of the men had abnormal semen parameters by the WHO Criteria. Azoospermia was found in 4.2% and 8.0% had severe oligospermia (<5 x 10⁶/ml).(6)

In another series from 1987 that attempted to identify a firm diagnosis of the male factor cause, 50% were categorized as "no demonstrable cause" and of the remaining 50%, half were categorized as "idiopathic" seminal abnormalities. In that study, 75% of male factor infertility problems were either undiagnosable or in the case of a sperm abnormality, no cause could be found.

Most of the identifiable causes were in single digit percentages. They included genetic, congenital, endocrine, iatrogenic and hormonal causes. The definitiveness of other possible causes, like varicocele, accessory gland infection and immunological abnormality, have been challenged because of the great overlap of these findings in the normally fertile population.,(8)

A review published in 2003 firmly states that 50% of male infertility is unexplained or idiopathic.(5) We have made some progress in identifying the causes both in the "no demonstrable cause" category and the seminal abnormalities. Still, the causes of a large proportion of male factor infertility cases are unknown, and many of those causes are thought to be genetic. As we leapfrog over abnormalities in the numerous genetically controlled steps to normal fertility with assisted reproductive technology, many in the field express concern about whether we are increasing the numbers of infertile males in the population.

Work-up of Man with Infertility

An abnormality in the semen analysis would trigger a focused medical evaluation of the male partner. The examiner should cover key screening points in the history and do a genital examination.

Using Semen Analysis to Detect Causes of Infertility

Although a profoundly depressed or absent sperm count in the semen is found in a small percentage of men, a determination of the cause can now be made in the majority of cases. Some are amenable to correction by surgery and others are caused by genetic mutations that the couple should know about in making decisions about childbearing.

Working up Azoospermia

Azoospermia is the complete absence of sperm in the semen and is seen in 2-4% of infertile males. Azoospermia could be caused by absent or extremely poor testicular function, in which case it is called nonobstructive azoospermia, or by a blockage in the genital tract, in which case it is called obstructive azoospermia.

Obstructive Azoospermia

The initial semen analysis is a good clue to the diagnosis of obstructive azoospermia because if the block is distal to the ejaculatory ducts, the semen will consist only of prostatic secretions. The volume would be very low, usually <1 ml and pH would be acidic. If the blockage is in the vas deferens or epididymis, the semen will have normal volume and alkaline pH but no sperm.

Low Volume, Low pH Azoospermia

Ejaculatory Duct Obstruction

In this case, the semen only contains prostatic fluid and has low volume and low pH. Both the vas deferens and the epididymis are palpable and are full and firm. The testis size is normal. A prostatic cyst occluding the ejaculatory ducts could cause this condition. It can be diagnosed by transrectal ultrasound. Excision of the obstruction may restore fertility.

Congenital Bilateral Absence of the Vas Deferens (CBAVD)

The semen is <1cc and pH is <7. The vas deferens cannot be palpated and only the head or a portion of the epididymis can be palpated. The testicles are normal size. In these men, the vas deferens, the distal two thirds of the epididymis and the seminal vesicles do not develop normally.

Thirty to 50% of men with obstructive azoospermia have congenital bilateral absence of the vas deferens (CBAVD). The most common genetic defect in these men is a mutation in the cystic fibrosis transmembrane regulator (CFTR) gene on chromosome 7. The normal function of CFTR is thought to be crucial to maintaining genital duct patency during very early development. Almost all (98%) men with cystic fibrosis have CBAVD.(9) Nearly 70% of men with CBAVD have at least one CFTR mutation. Some of these men may have two mutations with variable expression so that classical cystic fibrosis does not develop.(5) CBAVD may be the only manifestation of CFTR mutation in these men. Over 1000 mutations that affect the CFTR gene have been identified. CBAVD is also seen in men with genetic mutations that cause other defects of the genitourinary tract, like unilateral renal agenesis.

All patients with CBAVD should have genetic testing for CFTR mutations, transrectal ultrasound to determine the anatomy of the seminal vesicles, which are usually absent but can be cystic and dilated, and a renal ultrasound to check for renal agenesis.

Men with CBAVD can father children using assisted reproductive technology (ART) procedures, percutaneous or microsurgical epididymal duct aspiration (PESA or MESA) or testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). See below.

Genetic Counseling and CBAVD

Cystic Fibrosis (CF) is caused by an autosomal recessive gene mutation. If the man has two copies of this gene mutation and the woman has one copy of a CFTR mutation (is a carrier), 50% of the children will have two copies of a mutation and a high risk for classical CF and 50% will be carriers. If the mother does not have a CFTR mutation, all the children will be carriers because they all inherit one copy from the father. Approximately 4%, or one in twenty-five women, may have a CF mutation. The woman should be tested for a CFTR mutation, so that the couple will know what to expect. One option is preimplantation diagnosis-a cell is removed from the embryo and tested for CFTR mutations. With that knowledge, the couple may opt not to transfer an embryo that is homozygous for CFTR mutations.

Normal Volume, Normal pH Obstructive Azoospermia

In this case, the semen volume is 1.5ml or greater, the pH is 7.2 or more. Testicular size is normal. Depending on the level of obstruction, the vas and the epididymis can be firm to palpation. The testicular size and consistency are normal. The man may have a history of vasectomy, bilateral hernia repair or bilateral epididymitis.

Many men with this condition can be treated with microsurgery, bypassing the obstruction and reanastomosing vas to vas or epididymis to vas. Repair is not always possible, so aspiration of sperm-containing fluid with cryopreservation may be offered as part of the procedure.

Normal Volume, Normal pH Nonobstructive Azoospermia or Severe Oligospermia

In these patients, the vas and epididymis are normal; the testicles may be normal or small and soft. They may contain sperm, but at such low levels that sperm does not appear in the semen (azoospermia) or only in very small numbers (severe oligospermia).

There are many causes for testicular failure. A number of chromosomal defects have been identified-abnormal chromosome number, microdeletions or translocations. Others include maturation arrest of sperm, absence of the primordial germ cells ("Sertoli Cell Only Syndrome") or defective/absent androgen receptors ("androgen insensitivity syndrome"). There can be defects in pituitary hormone receptors or secretion. I would like to focus on the two most common chromosomal defects, microdeletions in the long arm of the Y chromosome and Klinefelter's syndrome.

Chromosomal Abnormalities in Men with Nonobstructive Azoospermia and Severe Oligospermia

Y Chromosome Microdeletions

In the mid 1990s, an important genetic defect associated with azoospermia and severe oligospermia was identified. On the active arm of the Y chromosome there are three areas, called "azoospermia factor" AZF a, b and c, that are critical to sperm development. Together, deletions in these three areas are found in 16% of cases with azoospermia and 14% of cases with severe oligospermia.(5) A deletion of AZFc is the most common of the three. Sperm can be retrieved from the testes in some of these patients for in vitro fertilization. One problem is that this genetic defect will be passed on to all male children. Couples must be counseled accordingly.

Klinefelter's Syndrome

Ninety percent of these patients have a 47XXY karyotype and 10% have a mosaic pattern of 46XY/47XXY. The main defect is deficient Leydig cell production of testosterone. The seminiferous tubules are sclerosed and hyalinized. The classical patient does not virilize at puberty, is tall, lacks secondary sex characteristics and may have mental deficiency. These patients are usually seen at puberty and put on androgen replacement. Many men with the same karyotype have sufficient testosterone for pubertal virilization and libido, but have insufficient testosterone for sperm production. On physical exam, the testicles are small and firm. Testosterone level is low and FSH and LH are elevated. Sperm can be retrieved from the testicular tissue of some of these men for in vitro fertilization.

Other Factors and Male Fertility

Cryptorchidism

When the testes do not descend into the scrotum and remain in the groin or abdomen, they do not develop normally. This condition is usually detected in infancy and corrected. Authorities recommend ochidopexy by two years of age because up until that age testicular histology is normal. But normal histology may not translate into normal function. Even after timely orchiopexy, some men will have azoospermia or oligospermia because of incomplete maturation at a very early stage of sperm development.(5) We have to consider that there may be more to cryptorchidism than just a defect in the physical location of the testis. There may be other genetic abnormalities as well.

Varicocele

Varicoceles are dilated veins of the pampinaform plexus, often visible and palpable in the scrotum. They develop at the time of puberty and are most frequently found on the left side, although they can be on the right or bilateral. They are present in over 15% of the male population. When you look at men who have had an abnormal semen analysis, 40% have a varicocele.

Most men who present with infertility and have a varicocele can have multiple abnormal semen parameters (concentration, motility and morphology) affecting their ability to establish a pregnancy. Testicular volume may be diminished on the affected side. Various proposed mechanisms include elevated testicular temperature and exposure to adrenal metabolites. Although many agree that varicoceles can adversely affect the testis, some authorities question whether repairing the varicocele in a man with impaired fertility will solve his fertility problem. There are evidence-based studies on both sides of the question.(10) Since many men with varicoceles have normal fertility potential, a varicocele should not be repaired simply because it is present, but only if one believes it will improve the fertility of men with impairment as demonstrated by abnormal semen parameters. On the other hand, many pediatric urologists suggest that an adolescent with a varicocele (and without a semen analysis) and with a small testis on the affected side may experience "catch up growth" if the varicocele is corrected. Whether this will prevent future fertility problems remains to be determined.

Heat: Is a warm testis a sick testis?

Spermatogenesis works best at a temperature several degrees below normal body temperature, hence the location of the testis in the scrotum. A testis that remains in the abdomen and one that is adjacent to a tangle of veins is definitely warmer, and this increased temperature is cited as a mechanism for testicular damage or dysfunction in the cases of cryptorchidism and varicocele. But should tight underwear, tights, athletic supporters and hot tubs be forbidden in the name of preserving fertility? The benefit of changing clothing is questionable, but avoiding hot tubs and saunas, particularly if the sperm count is borderline, is probably a good idea when trying for a pregnancy.(15)

Drugs

A number of drugs can be associated with male infertility. It is not useful to give an exhaustive list in this Cyberounds^®. Suffice to say, do a thorough review of prescription, over-the-counter and recreational drugs, as well as habits. A few examples are in Table 4.

Cancer Treatment and Male Fertility

Both chemotherapy and radiation affect rapidly dividing cells and can destroy or severely compromise fertility. Radiation can cause chromosomal damage as well. A man who anticipates fathering children should consider cryopreserving (banking) his sperm prior to his cancer treatment.

Men who have already had cancer treatment and have azoospermia may still have viable sperm in the testes that can be recovered by epididymal duct aspiration or testicular sperm extraction.

Toxins

Environmental and workplace hazards can affect male fertility. Consult http://www.cdc.gov/niosh/malereproduction for more information.

Treating Male Infertility

In some instances, surgery directly on the genital tract can re-establish normal fertility. Examples are correction of azoospermia by relieving obstruction: reversal of a vasectomy, bypassing epididymal scarring or removing a prostatic cyst. When these repair procedures are undertaken, the surgeon may also retrieve a sperm specimen for cryopreservation because not all surgeries can achieve a functional anastomosis. As mentioned above, repairing a varicocele can improve testicular growth in adolescents and semen parameters and fertility in some men with infertility.

Some men with hypothalamic/pituitary hormone deficiencies can be treated with gonadotropin therapy. This may be the case in 1-2% of the treatment group.(5)

Maximizing Male Fertility

In most cases the goal is to maximize male fertility potential. As mentioned before, two to three days of abstinence before intercourse increases the volume and sperm content of the ejaculate.

The sperm can be separated from the other elements in the semen and concentrated. This concentrated specimen is used for intrauterine insemination (IUI). In this procedure, the cervix is bypassed and the sperm pellet is released high in the uterine cavity. It is timed with ovulation, either natural, or stimulated.

Cryopreservation

Sperm specimens can be frozen ("banked") for future use. High quality cryopreserved sperm have efficacy very close to fresh specimens, although there is always some fall-off in quality. With poorer specimens, the fall-off will be greater.

Special Assisted Reproductive Technologies to Boost Male Fertility

Surgical Sperm Recovery

I have mentioned, at several points in the above discussion, that when there is an anatomical blockage or very poor testicular function, sperm can be retrieved directly from the testis either percutaneously or during surgery.

The most desirable situation is to aspirate from the epididymal duct because that would contain the most mature sperm. Aspiration from a seminiferous tubule would be next, followed by biopsy of actual testicular tissue. Special separation procedures are required to extract sperm from the tissue. In all cases, sperm not used for an immediate fertilization attempt should be cryopreserved so that the procedure would not have to be repeated.

These procedures all have acronyms (listed below) and the one chosen depends on the judgment of the surgeon about the clinical situation.

PESA: Percutaneous Epididymal Sperm Aspiration
MESA: Microsurgical Epididymal Sperm Aspiration
TESA: Testicular Sperm Aspiration
TESE: Testicular Sperm Extraction

Table 5 shows a series from one author that will give you an idea of the relative frequency of the conditions for which these procedures are used.

*adapted from Immarrone, reference 5.

Intracytoplasmic Sperm Injection (ICSI)

Some male factor infertility is due to defects in the final steps of fertilization, processes that include attraction to the oocyte, increased motility, the penetration of the zona pellucida and binding to the egg cell membrane. These sperm cannot fertilize an egg in vitro, when the egg and sperm are simply placed together.

In the late 1980s, several techniques were developed, using extremely fine micropipettes, to inject the sperm through the barrier around the egg and achieve fertilization. In partial zonal dissection (PZD), the sperm was placed partly through the zona pellucida and in subzonal insemination (SUZI), the sperm was placed just beneath the zona. There were still sperm that were unable to enter the egg using these procedures.

With intracytoplasmic sperm injection (ICSI), the sperm is injected directly into the egg cytoplasm. In 1992, three full-term pregnancies using this technique were reported.(11) Now ICSI has largely replaced the other micropipette procedures, PZD and SUZI, and is used in about half of the in vitro fertilization-embryo transfer (IVF-ET) cycles reported by the CDC.(2)

There have been concerns about damage to the egg cytoplasm and about adherent substances being injected along with the sperm. Long-term studies are underway to follow children resulting from this procedure to detect developmental and genetic problems. One study of two-year-old children did not detect any significant differences compared with naturally conceived children. There was a trend toward more genital tract abnormalities in males.(12) Further follow-up will have to be done to determine whether there is an increased prevalence of fertility problems among the male children conceived by ICSI.

Summary and Conclusions

Male factor infertility has been increasingly diagnosed as the primary problem in infertile couples, as many as 40% of cases. The causes of infertility range from obstructive, environmental, developmental, to genetically mediated defects in the sperm. As genetic medicine research progresses, more genetic causes are being identified. Only a small portion of infertile males can be definitively treated and the cause of their infertility corrected. In most instances, techniques and procedures are aimed at maximizing male fertility. The most advanced procedures, testicular sperm extraction and intracytoplasmic sperm injection, now allow formerly "sterile" men to become fathers.

1. www.cdc.gov/reproductivehealth/art.htm: Reports on assisted reproductive technology in the United States.

2. www.cdc.gov/niosh/malrepro.html: Male reproduction workplace hazards.

3. www.asrm.org: American Society of Reproductive Medicine.