Several factors affect fertility.
A healthy egg must travel down the fallopian tube where it is fertilized by healthy sperm. Then it must complete the travel through the tube and implant in the lining of the uterus. Finally, the woman s body must provide a supportive environment for the developing embryo. The American Society for Reproductive Medicine estimates that 6.1 million people in the U.S. are affected by infertility. About one-third of cases are caused by male factors, such as low sperm counts or poor quality sperm.