Fertility is the natural ability to reproduce (make babies).It depends on many things like nutrition, sexual behaviour, culture, hormones, health status, genetics and emotions. Most women's cycle is about 28days long and she is most fertile on the days either side of ovulation which is usually 12-16 days before her next period starts. Men can ejaculate and make sperm at any time, but the amount and quality can be lower sometimes according to his cycle, which is irregular.
Attribution: Straight Talk Foundation