Nicotine can be toxic to sperm in cervical mucus. In women, smoking may cause estrogen levels to change, depleting egg production. In men, smoking may lower sperm count and motility. In men, excessive alcohol use can lower sperm count. Speak with your doctor about other drugs that may affect fertility.
Sperm production is affected by temperature.
High fevers, excessive heat in work environments, saunas, and hot tubs can decrease male fertility by increasing testicular heat. In women, low body fat affects ovulation, while excess weight in men raises body temperature with corresponding decrease in sperm production. Corresponding problems with irregular menstruation contribute to the fertility problem. If you are having difficulty becoming pregnant or are considering pregnancy, discuss these issues with your doctor. Also, review your life situation for any excess stress or anxiety which can effect ovulation.