There are a number of factors that can affect fertility in both men and women. These are outlined below.

1. Genetic factors

  • A Robertsonian translocation in either partner may cause recurrent spontaneous abortions or complete infertility.

2. General factors

  • Diabetes mellitus, thyroid disorders, adrenal disease
  • Weight--Being overweight, or obese, reduces both male and female fertility. In women, being overweight can affect ovulation. Being underweight can also have an impact on fertility, particularly for women, who will not ovulate if they are severely underweight.

3. Hypothalamic-pituitary factors

  • Hyperprolactinemia
  • Hypopituitarism
  • The presence of anti-thyroid antibodies is associated with an increased risk of unexplained subfertility with an odds ratio of 1.5 and 95% confidence interval of 1.1–2.0.

4. Environmental factors

  • Toxins such as glues, volatile organic solvents or silicones, physical agents, chemical dusts, and pesticides.[23][24] Tobacco smokers are 60% more likely to be infertile than non-smokers.

5. Sexually transmitted infections (STIs))

There are several STIs that can cause infertility. For example, chlamydia can damage the fallopian tubes in women,

and cause swelling and tenderness of the scrotum (the pouch containing the testes) in men.

6. Smoking

As well as affecting your general and long-term health, smoking can also adversely affect fertility.

7. Stress

If either you or your partner are stressed it may affect your relationship. Stress can contribute to a loss of libido (sex drive), which in turn can reduce the frequency of sexual intercourse. Severe stress may also affect female ovulation and limit sperm production.