There are other reasons besides the most common such as alcoholism and smoking that deter pregnancy. Other reasons to include in this summation are:
Weight problems in that being underweight or overweight could interfere with the conception process. Therefore it is advised to follow a healthy diet and balanced workout regime to improve the odds of pregnancy.
Sleep Deprivation in that sleep deprived could trigger negative emotions and may backfire on physical and mental health. It could increase stress and force one to eat more – increasing cravings for processed, junk food thereby affecting the body weight and even the process of ovulation.
Stress is often cited as a causative factor for infertility. The practice of meditation is to keep all forms of stress at bay, as it could it cause problems with the ovulation process to the end of not ovulating regularly or in a timely manner.
Prolonged usage of birth control pills that are used for birth control and sometimes for the treatment of endometriosis and PCOS could be the reason why one fails to get pregnant.
Nervousness during intercourse in that Stress is a driving factor even when one has not already conceived, even during sex. It could spike cortisol levels thereby preventing the release of hormones and stopping the body from responding the way it should in order to get pregnant.