In a normal menstrual cycle, the egg is produced every month in the ovary. The matured egg is released for fertilization. Conception happens when the egg fertilizes with the help of sperm in the uterus. In PCOD women, the egg is not released and gets entrapped in the ovary. This leads to the growth of many cysts, called the polycystic ovary. When the egg is not released, periods become irregular.