It was observed that swim rate of sperm changes in microgravity. Sperm swim with higher velocity in microgravity. The fertilization might be affected by this mobility changes in sperm and this led to reduction in sperm motility under microgravity. Follicle-Stimulating Hormone (FSH) that is responsible for ovulation in women by triggering egg maturity and stimulating sperm production in men can be damaged by microgravity. Therefore, ovulations and triggering of egg maturity and production of sperm may not take place. Higher acidity of outer vagina due to fluid distribution at the upper part of the body might kill the sperm or reduce sperm counts. Microgravity environment reduced the thickening of the endometrium to the extent that eggs cannot be planted (cause non-implantations).