Understanding the Basics: What Causes Infertility in Men and Women?
Infertility, defined as the inability to conceive after one year of regular, unprotected intercourse (or six months for women aged 35 and older), is a more common issue than many realize, affecting millions globally. It’s crucial to understand that fertility challenges are not solely a “woman’s problem”; in approximately one-third of cases, the issue lies with the male partner, another third with the female partner, and the remaining third involves both partners or has unexplained causes.
To achieve pregnancy, a complex series of events must occur successfully. In women, this involves the regular release of a healthy egg from the ovary (ovulation), the egg’s travel through the fallopian tube, fertilization by sperm, and the implantation of the fertilized egg in the uterus. In men, it requires the production of healthy sperm in sufficient numbers, their ability to move effectively (motility), and their successful delivery into the female reproductive tract. Disruptions at any point in these processes can lead to infertility.
Here’s a detailed look at the primary causes of infertility in both men and women:
Causes of Infertility in Men:
Male infertility typically arises from problems in the production, function, or delivery of sperm.
Sperm Disorders: These are the most common causes of male infertility and encompass several issues:
- Low Sperm Count (Oligospermia): Having fewer than 15 million sperm per milliliter of semen significantly reduces the chances of fertilization.
- Poor Sperm Motility (Asthenospermia): If sperm cannot swim effectively towards the egg, fertilization is less likely. Healthy sperm exhibit a progressive, forward movement.
- Abnormal Sperm Morphology (Teratospermia): Sperm with an irregular shape may have difficulty penetrating the egg. A healthy sperm typically has an oval head and a long tail. * Absence of Sperm (Azoospermia): This can be due to blockages in the reproductive tract or the testicles not producing sperm.
Varicocele: This condition involves the swelling of the veins that drain the testicle. It’s the most common reversible cause of male infertility. The enlarged veins can increase the temperature in the testicles, which can negatively impact sperm production and quality.
Infections: Certain infections can interfere with sperm production or health, or cause scarring that blocks the passage of sperm. These include:
- Sexually Transmitted Infections (STIs): Chlamydia and gonorrhea can cause epididymitis (inflammation of the epididymis) or orchitis (inflammation of the testicles).
- Other Infections: Mumps orchitis (inflammation of the testicles due to the mumps virus after puberty) can also impair fertility.
Ejaculation Issues: Problems with ejaculation can prevent sperm from reaching the egg:
- Retrograde Ejaculation: Semen enters the bladder instead of exiting the penis during orgasm. This can be caused by diabetes, spinal injuries, medications, or surgery.
- Premature Ejaculation: Ejaculating too quickly may prevent sufficient sperm from being deposited in the vagina.
- Anejaculation: The inability to ejaculate.
Obstruction: Blockages in the tubes that carry sperm (such as the epididymis, vas deferens, or ejaculatory ducts) can prevent sperm from being ejaculated. These blockages can be caused by infections, surgery (including vasectomy), injury, or congenital defects like cystic fibrosis.
Hormonal Imbalances: Hormones produced by the hypothalamus, pituitary gland, and testicles are crucial for sperm production. Imbalances in hormones like testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) can impair fertility.
Antibodies that Attack Sperm (Immunologic Infertility): In some cases, the man’s immune system mistakenly identifies sperm as harmful invaders and produces antibodies that attack them, impairing their movement and function.
Tumors: Cancers and non-malignant tumors can directly affect the male reproductive organs or the glands that produce reproductive hormones. Treatments for tumors, such as surgery, radiation, or chemotherapy, can also impact male fertility.
Undescended Testicles (Cryptorchidism): If one or both testicles fail to descend into the scrotum during fetal development, it can affect sperm production, as the higher temperature in the abdomen is not conducive to sperm development.
Lifestyle Factors and Environmental Exposures:
- Smoking: Damages sperm quality and reduces sperm count.
- Excessive Alcohol Consumption: Can lower testosterone levels and affect sperm production.
- Drug Use (including anabolic steroids, marijuana, cocaine): Negatively impacts sperm count, motility, and morphology. Anabolic steroids can severely harm sperm production.
- Obesity: Can affect hormone levels and sperm quality due to increased body temperature and metabolic changes.
- Exposure to Environmental Toxins: Pesticides, herbicides, heavy metals (like lead), and radiation can damage sperm.
- Heat Exposure: Frequent use of hot tubs, saunas, and tight clothing can increase testicular temperature and impair sperm production.
Genetic Disorders: Conditions like Klinefelter syndrome, cystic fibrosis, and other chromosomal abnormalities can affect sperm production and function.
Causes of Infertility in Women:
Female infertility can result from a wide range of issues affecting ovulation, the fallopian tubes, the uterus, or hormonal balance.
Ovulation Disorders: These are the most common cause of female infertility, affecting the release of eggs from the ovaries. Examples include:
- Polycystic Ovary Syndrome (PCOS): A hormonal imbalance that can cause irregular or absent ovulation, along with other symptoms like irregular periods, cysts on the ovaries, and excess androgen levels. It’s the most common cause of female infertility.
- Hypothalamic Dysfunction: The hypothalamus in the brain controls the pituitary gland, which produces hormones (FSH and LH) that stimulate ovulation. Stress, weight changes, or eating disorders can disrupt this process.
- Primary Ovarian Insufficiency (POI) or Premature Ovarian Failure: The ovaries stop working normally before the age of 40, leading to a cessation of egg production and decreased estrogen levels. This can be caused by autoimmune diseases, genetic conditions, or chemotherapy/radiation.
- Hyperprolactinemia: Excess production of prolactin (the hormone that stimulates breast milk production) by the pituitary gland can interfere with ovulation. This can be caused by pituitary tumors or certain medications.
- Thyroid Disorders: Both an overactive (hyperthyroidism) and underactive (hypothyroidism) thyroid gland can affect the menstrual cycle and ovulation.
Fallopian Tube Damage or Blockage (Tubal Infertility): Damaged or blocked fallopian tubes prevent the egg from traveling to the uterus and sperm from reaching the egg. Common causes include:
- Pelvic Inflammatory Disease (PID): Often caused by untreated STIs like chlamydia and gonorrhea, PID can lead to scarring and blockage of the fallopian tubes.
- Endometriosis: The growth of uterine-like tissue outside the uterus can cause adhesions (scar tissue) that block the fallopian tubes.
- Prior Ectopic Pregnancy: A pregnancy that implants outside the uterus, often in the fallopian tube, can damage the tube.
- Pelvic Surgery: Previous surgeries, such as for appendicitis or ovarian cysts, can sometimes lead to scar tissue formation that blocks the fallopian tubes.
Uterine or Cervical Issues: Problems with the uterus or cervix can interfere with implantation or increase the risk of miscarriage:
- Uterine Fibroids and Polyps: These non-cancerous growths in the uterus can distort the uterine cavity, block the fallopian tubes, or interfere with implantation. Submucosal fibroids (those growing into the uterine cavity) are more likely to affect fertility.
- Congenital Uterine Abnormalities: Some women are born with an abnormally shaped uterus (e.g., septate uterus) that can affect fertility.
- Cervical Stenosis: Narrowing of the cervix can be caused by an inherited malformation or damage to the cervix, potentially hindering sperm from entering the uterus.
- Cervical Mucus Problems: The cervix produces mucus that helps sperm travel to the egg. If the mucus is thick or hostile to sperm, it can make conception difficult.
Endometriosis: As mentioned earlier, this condition can not only block fallopian tubes but also affect the ovaries and the general pelvic environment, potentially interfering with fertilization and implantation.
Primary Ovarian Insufficiency (POI): While also causing ovulation issues, POI is a distinct condition where the ovaries cease functioning prematurely.
Pelvic Adhesions: Bands of scar tissue that can form after pelvic infection, appendicitis, endometriosis, or surgery, binding organs together and potentially affecting the ovaries, fallopian tubes, and uterus.
Cancer and its Treatment: Certain cancers, especially those affecting the reproductive organs, can reduce fertility. Treatments like radiation and chemotherapy can also damage the ovaries.
Lifestyle Factors and Environmental Exposures:
- Age: A woman’s fertility gradually declines with age, especially after the mid-30s, due to a decrease in the number and quality of eggs.
- Smoking: Damages the ovaries and fallopian tubes, increases the risk of miscarriage and ectopic pregnancy, and may prematurely deplete eggs.
- Excessive Alcohol Consumption: Can reduce fertility.
- Obesity and Being Underweight: Can disrupt ovulation. Achieving a healthy Body Mass Index (BMI) is important for regular ovulation. Eating disorders can severely impact fertility.
- Excessive Exercise: In some women who are not overweight, frequent, strenuous exercise can be linked to ovulation problems.
- Autoimmune Disorders: Conditions like lupus and rheumatoid arthritis can affect fertility. The immune system may mistakenly attack reproductive organs.
Other Medical Conditions: Chronic illnesses such as diabetes, certain autoimmune diseases, and genetic disorders can also contribute to female infertility.
Understanding the diverse causes of infertility in both men and women is the first step towards seeking appropriate diagnosis and treatment. If you and your partner are experiencing difficulty conceiving, consulting a fertility specialist for a thorough evaluation is highly recommended. They can conduct necessary tests to identify the underlying cause and discuss suitable treatment options to help you achieve your family-building goals.