Most pregnancies occur during the first six cycles of intercourse in the fertile phase. Overall, after 12 months of unprotected intercourse, approximately 85 percent of couples will become pregnant. Over the next 36 months, about 50 percent of the remaining couples will go on to conceive spontaneously.
Symptoms
- Each month the pituitary gland in
a woman's brain sends a signal to her ovaries to prepare an egg for
ovulation.
- The pituitary hormones —
follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) —
stimulate the ovaries to release an egg. This is called ovulation. It is
during this time a woman is fertile (usually about day 14 of her menstrual
cycle).
- The egg travels through the
fallopian tube and can be fertilized about 24 hours after its release.
Conception is more likely to occur when intercourse takes place one to two
days prior to ovulation.
- For pregnancy to occur, a sperm
must unite with the egg in the fallopian tube during this time. Sperm are
capable of fertilizing the egg for up to 72 hours and must be present in
the fallopian tube at the same time as the egg for conception to occur. In
order for a sperm to reach an egg, the man must have an erection and
ejaculate enough semen to deliver the sperm into the vagina. There must be
enough sperm, and it must be the right shape and move in the right way. In
addition, the woman must have a healthy vaginal and uterine environment so
that the sperm can travel to the egg.
- If fertilized, the egg moves into
the uterus where it attaches to the uterine lining and begins a nine-month
process of growth.
A number of things can cause impaired sperm count or mobility, or impaired ability to fertilize the egg. The most common causes of male infertility include abnormal sperm production or function, impaired delivery of sperm, general health and lifestyle issues, and overexposure to certain environmental elements.
- Impaired shape and movement of
sperm.
Sperm must be properly shaped and able to move rapidly and accurately
toward the egg for fertilization to occur. If the shape and structure
(morphology) of the sperm are abnormal or the movement (motility) is
impaired, sperm may not be able to reach or penetrate the egg.
- Low sperm concentration. A normal sperm concentration is
greater than or equal to 20 million sperm per millilitre of semen. A count
of 10 million or fewer sperm per millilitre of semen indicates low sperm
concentration (sub fertility). A count of 40 million sperm or higher per millilitre
of semen indicates increased fertility. Complete failure of the testicles
to produce sperm is rare, affecting very few infertile men.
- Varicocele. A varicocele is a varicose vein
in the scrotum that may prevent normal cooling of the testicle, leading to
reduced sperm count and motility.
- Undescended testicle. Undescended testicle occurs when
one or both testicles fail to descend from the abdomen into the scrotum
during foetal development. Because the testicles are exposed to the higher
internal body temperature, compared with the temperature in the scrotum,
sperm production may be affected.
- Testosterone deficiency (male
hypogonadism). Infertility can result from disorders of the testicles
themselves, or an abnormality affecting the hypothalamus or pituitary
gland in the brain that produces the hormones that control the testicles.
- Genetic defects. In the genetic defect
Klinefelter's syndrome, a man has two X chromosomes and one Y chromosome
instead of one X and one Y. This causes abnormal development of the
testicles, resulting in low or absent sperm production and possibly low
testosterone.
- Infections. Infection may temporarily affect
sperm motility. Repeated bouts of sexually transmitted diseases (STDs),
such as Chlamydia and gonorrhoea, are most often associated with male
infertility. These infections can cause scarring and block sperm passage.
If mumps, a viral infection usually affecting young children, occurs after
puberty, inflammation of the testicles can impair sperm production.
Inflammation of the prostate (Prostatitis), urethra or epididymis also may
alter sperm motility.
- Sexual issues. Often treatable, problems with
sexual intercourse or technique may affect fertility. Difficulties with
erection of the penis (erectile dysfunction), premature ejaculation,
painful intercourse (dyspareunia), or psychological or relationship problems
can contribute to infertility. Use of lubricants such as oils or petroleum
jelly can be toxic to sperm and impair fertility.
- Retrograde ejaculation. This occurs when semen enters the
bladder during orgasm rather than emerging out through the penis. Various
conditions can cause retrograde ejaculation including diabetes, bladder,
prostate or urethral surgery, and the use of certain medications.
- Blockage of epididymis or
ejaculatory ducts. Some men are born with blockage of the part of the
testicle that contains sperm (epididymis) or ejaculatory ducts. Some men
lack the tube that carries sperm (vas deferens) from the testicle out to
the opening in the penis.
- No semen (ejaculate). The absence of ejaculate may
occur in men with spinal cord injuries or diseases. This fluid carries the
sperm from the penis into the vagina.
- Misplaced urinary opening
(hypospadias). A birth defect can cause the urinary (urethral)
opening to be abnormally located on the underside of the penis. If not
surgically corrected, this condition can prevent sperm from reaching the
woman's cervix.
- Anti-sperm antibodies. Antibodies that target sperm and
weaken or disable them usually occur after surgical blockage of part of
the vas deferens for male sterilization (vasectomy). Presence of these
antibodies may complicate the reversal of a vasectomy.
- Cystic fibrosis. Men with cystic fibrosis often
have missing or obstructed vas deferens.
- Emotional stress. Stress may interfere with certain
hormones needed to produce sperm. Your sperm count may be affected if you
experience excessive or prolonged emotional stress. A problem with
fertility itself can sometimes become long term and discouraging,
producing more stress. Infertility can affect social relationships and
sexual functioning.
- Malnutrition. Deficiencies in nutrients such as
vitamin C, selenium, zinc and folate may contribute to infertility.
- Obesity. Increased body mass may be
associated with fertility problems in men.
- Cancer and its treatment. Both radiation and chemotherapy
treatment for cancer can impair sperm production, sometimes severely. The
closer radiation treatment is to the testicles, the higher the risk of
infertility. Removal of one or both testicles due to cancer also may
affect male fertility.
- Alcohol and drugs. Alcohol or drug dependency can be
associated with poor health and reduced fertility. The use of certain
drugs also can contribute to infertility. Anabolic steroids, for example,
which are taken to stimulate muscle strength and growth, can cause the
testicles to shrink and sperm production to decrease.
- Other medical conditions. A severe injury or major surgery
can affect male fertility. Certain diseases or conditions, such as
diabetes, thyroid disease, Cushing's syndrome, or anaemia may be
associated with infertility.
- Age. A gradual decline in fertility is
common in men older than 35.
- Pesticides and other chemicals. Herbicides and insecticides may
cause female hormone-like effects in the male body and may be associated
with reduced sperm production and testicular cancer. Lead exposure may
also cause infertility.
- Overheating the testicles. Frequent use of saunas or hot tubs
can elevate your core body temperature. This may impair your sperm
production and lower your sperm count.
- Substance abuse. Use of cocaine or marijuana may
temporarily reduce the number and quality of your sperm.
- Tobacco smoking. Men who smoke may have a lower
sperm count than do those who don't smoke.
The most common causes of female infertility include fallopian tube damage or blockage, endometriosis, ovulation disorders, elevated prolactin, polycystic ovary syndrome (PCOS), early menopause, benign uterine fibroids and pelvic adhesions.
- Fallopian tube damage or blockage. Fallopian tube damage usually
results from inflammation of the fallopian tube (salpingitis). Chlamydia,
a sexually transmitted disease, is the most frequent cause. Tubal
inflammation may go unnoticed or cause pain and fever. Tubal damage is the
major risk factor of a pregnancy in which the fertilized egg is unable to
make its way through the fallopian tube to implant in the uterus (ectopic
pregnancy). One episode of Tubal infection may cause fertility
difficulties. The risk of ectopic pregnancy increases with each occurrence
of Tubal infection.
- Endometriosis. Endometriosis occurs when the
uterine tissue implants and grows outside of the uterus — often affecting
the function of the ovaries, uterus and fallopian tubes. These implants
respond to the hormonal cycle and grow, shed and bleed in sync with the
lining of the uterus each month, which can lead to scarring and
inflammation. Pelvic pain and infertility are common in women with
endometriosis.
- Ovulation disorders. Some cases of female infertility
are caused by ovulation disorders. Disruption in the part of the brain
that regulates ovulation can cause low levels of Luteinizing hormone (LH)
and follicle-stimulating hormone (FSH). Even slight irregularities in the
hormone system can affect ovulation. Specific causes of
hypothalamic-pituitary disorders include injury, tumours, excessive
exercise and starvation.
- Elevated prolactin
(hyperprolactinemia). The hormone prolactin stimulates breast milk
production. High levels in women who aren't pregnant or nursing may affect
ovulation. An elevation in prolactin levels may also indicate the presence
of a pituitary tumour. In addition, some drugs can elevate levels of prolactin.
Milk flow not related to pregnancy or nursing can be a sign of high
prolactin.
- Polycystic ovary syndrome (PCOS). In PCOS, your body produces too
much androgen hormone, which affects ovulation. PCOS is associated with
insulin resistance and obesity.
- Early menopause (premature ovarian
failure).
Early menopause is the absence of menstruation and the early depletion of
ovarian follicles before age 35. Although the cause is often unknown,
certain conditions are associated with early menopause, including immune
system diseases, radiation or chemotherapy treatment, and smoking.
- Benign uterine fibroids. Fibroids are benign tumours in
the wall of the uterus and are common in women in their 30s. Occasionally
they may cause infertility by blocking the fallopian tubes.
- Pelvic adhesions. Pelvic adhesions are bands of
scar tissue that bind organs after pelvic infection, appendicitis, or
abdominal or pelvic surgery. This scar tissue formation may impair
fertility.
- Medications. Temporary infertility may occur
with the use of certain medications. In most cases, fertility is restored
when the medication is stopped.
- Thyroid problems. Disorders of the thyroid gland,
either too much thyroid hormone (hyperthyroidism) or too little
(hypothyroidism), can interrupt the menstrual cycle and cause infertility.
- Cancer and its treatment. Certain cancers — particularly
female reproductive cancers — often severely impair female fertility. Both
radiation and chemotherapy may affect a woman's ability to reproduce.
Chemotherapy may impair reproductive function and fertility in men and
women.
- Other medical conditions. Medical conditions associated
with delayed puberty or amenorrhea, such as Cushing's disease, sickle cell
disease, HIV/AIDS, kidney disease and diabetes, can affect a woman's
fertility.
- Caffeine intake. Excessive caffeine consumption
reduces fertility in the female.
- Age. After about age 32, a woman's
fertility potential gradually declines. Infertility in older women may be
due to a higher rate of chromosomal abnormalities that occur in the eggs
as they age. Older women are also more likely to have health problems that
may interfere with fertility. The risk of miscarriage also increases with
a woman's age. A gradual decline in fertility is possible in men older
than 35.
- Tobacco smoking. Men and women who smoke tobacco
may reduce their chances of becoming pregnant and reduce the possible
benefit of fertility treatment. Miscarriages are more frequent in women
who smoke.
- Alcohol use. For women, there's no safe level
of alcohol use during conception or pregnancy. Moderate alcohol use does
not appear to decrease male fertility.
- Being overweight. Among American women, infertility
often is due to a sedentary lifestyle and being overweight.
- Being underweight. Women at risk include those with
eating disorders, such as anorexia nervosa or bulimia, and women following
a very low-calorie or restrictive diet. Strict vegetarians also may
experience infertility problems due to a lack of important nutrients such
as vitamin B-12, zinc, iron and folic acid.
- Too much exercise. In some studies, exercising more
than seven hours a week has been associated with ovulation problems.
Strenuous exercise may also affect success of in vitro fertilization. On
the other hand, not enough exercise can contribute to obesity, which also
increases infertility.
- Caffeine intake. Studies are mixed on whether
drinking too much caffeine may be associated with decreased fertility.
Some studies have shown a decrease in fertility with increased caffeine
use while others have not shown adverse effects. If there are effects,
it's likely that caffeine has a greater impact on a woman's fertility than
on a man's. High caffeine intake does appear to increase the risk of
miscarriage.
- If you plan to conceive and you're
a woman older than 30 or haven't had a menstrual flow for longer than six
months, seek a medical evaluation.
- If you have a history of irregular
or painful menstrual cycles, pelvic pain, endometriosis, pelvic
inflammatory disease (PID) or repeated miscarriages, schedule an
appointment with your doctor sooner.
- If you're a man with a low sperm
count or a history of testicular, prostate or sexual problems, consider
seeking help earlier.