Other facts about infertility include:

• Women are most fertile during ovulation, which occurs around the 14th day of their menstrual cycle. However, the exact time of ovulation varies among women due to normal differences in cycle length.
  
  
• After ovulation occurs, an egg remains viable for about 24 hours. Sperm, on the other hand, can live in a woman's reproductive tract up to 72 hours.
  
  
• The sexually transmitted diseases (STDs) chlamydia and gonorrhea are the most important preventable causes of infertility, according to the U.S. Centers for Disease Control and Prevention (CDC). If untreated, up to 40 percent of women with these conditions will develop pelvic inflammatory disease (PID), which can lead to infertility.
  
• The number of children born as a result of assisted reproductive technologies is growing each year. In 2005, that number was more than 52,000 according to the CDC -- compared to 14,500 in 1996.