Common Causes of Infertility
1. Female Factors
- Ovulation Disorders: Problems with the release of eggs from the ovaries are the most common cause of female infertility. Conditions such as polycystic ovary syndrome (PCOS), thyroid disorders, premature ovarian failure, and hormonal imbalances can disrupt ovulation[1][2][3][4].
- Tubal Factors: Blocked or damaged fallopian tubes, often due to infections (such as pelvic inflammatory disease), endometriosis, or previous surgeries, can prevent sperm from reaching the egg or block the fertilized egg from reaching the uterus[5][6][2][3][4].
- Uterine or Cervical Factors: Abnormalities such as fibroids, polyps, scar tissue, or congenital malformations of the uterus or cervix can interfere with implantation or the passage of sperm[5][7][2][3][4].
- Endometriosis: The presence of tissue similar to the uterine lining outside the uterus can cause inflammation, scarring, and impaired function of the ovaries, fallopian tubes, and uterus[6][2][3].
- Age: Female fertility declines with age, particularly after the mid-30s, due to a decrease in both the quantity and quality of eggs[5][4][8].
2. Male Factors
- Sperm Disorders: Low sperm count, poor sperm motility, abnormal sperm shape, or blockages preventing sperm delivery are common causes of male infertility[1][5][9][3][4].
- Hormonal Imbalances: Issues with testosterone or other hormones can affect sperm production[1][3][4].
- Genetic and Structural Issues: Genetic disorders (such as cystic fibrosis), varicoceles (enlarged veins in the scrotum), or structural blockages can impair fertility[3][4].
- Lifestyle and Environmental Factors: Smoking, excessive alcohol use, drug use, exposure to toxins or radiation, and high testicular temperatures can negatively impact sperm quality[10][11][3][8].
3. Combined and Unexplained Factors
- In about 20–25% of cases, both partners contribute to infertility, and in 10–15% of cases, no clear cause is found after standard evaluation (unexplained infertility)[1][5][9][4].
4. Other Contributing Factors
- Chronic Medical Conditions: Diabetes, thyroid disorders, and autoimmune diseases can affect fertility in both men and women[10][3].
- Infections: Sexually transmitted infections (such as chlamydia or gonorrhea) can cause scarring and blockages in the reproductive tract[6][3][12].
- Lifestyle and Behavioral Factors: Obesity, being underweight, excessive or insufficient exercise, poor nutrition, and high stress levels can all play a role in infertility[11][3][8].
Importance of Comprehensive Evaluation
Because infertility can result from multiple, overlapping causes, a thorough evaluation of both partners is recommended. This typically includes a detailed medical and reproductive history, physical examinations, hormone assessments, semen analysis, and imaging or specialized tests as needed[7][9].
