Egg & Sperm Facts

Historically the thought of what sex a baby will be was assumed to be related to the gamete of the mother, but we now realize that sperm, not eggs, determine a baby’s gender. This is good since it has allowed us to address male fertility issues instead of looking only to women for causes of infertility. Want to know more? Here are a few facts about human eggs and sperm that you may not already know.

  • Many people are aware that women are born with all the eggs they will ever have– usually about 2 million. However, a fact that is less known is that even at birth, baby girls have already lost most of the eggs their body originally created. At just five months’ gestation, female fetuses can have more than 7 million oocytes (immature egg cells). Interestingly, that same woman will only lose about 500,000 eggs from puberty until she reaches menopause.
  • Until recently, the only way to freeze eggs was to apply a slow freeze process in the IVF laboratory. While this method worked fairly well for sperm and even embryos, it presented some problems for eggs. Basically, when frozen slowly, the eggs would develop ice crystals, which caused the eggs to break down. Since it was impossible for scientists to remove all of the excess water from the eggs, they had to find a better preservation method. Finally, the process of vitrification was developed. Through vitrification, eggs and embryos are frozen in a fast freeze process.
  • The viability of eggs decreases drastically in a relatively short time span. While women in their early twenties can expect about 90 percent of their eggs to be viable, by the time they reach their forties, that number drops to around 10 percent.
  • Human egg cells are the largest cells in the body but are microscopic, and sperm cells are even smaller. Just how little are they? Sperm are roughly 1/500ths of an inch long— about 30 times smaller than the eggs they attempt to fertilize.
  • Although sperm look like any other cell in the body when they are first formed, they go through some drastic changes during their lifespan to gain the appearance of the mature sperm cell that we all think about when thinking of what these cells look like.
  • Your habits affect your sperm count and quality. Studies have shown that certain activities like smoking, laptop computers, cell phones in front pockets, and excessive TV viewing can result in a reduction in sperm quality and quantity, respectively. Because of this, male fertility specialists recommend that men who are making concerted efforts to conceive should stop smoking and maintain a healthy lifestyle.