Understanding Pregnancy and Infertility

Sperm Development

Sperm are male reproductive cells produced in the testicles. Men produce millions of sperm each day. Sperm developing inside the testicles take nearly 90 days to fully mature. Sperm are held within a coiled tube of the testicle called the epididymis until they are ejaculated. Sperm mixes with fluids to form semen before it is ejaculated. The semen helps nourish the sperm.

Egg Development

Eggs are female reproductive cells stored in the ovaries. Women are born with their entire supply of eggs which means the quality and quantity of eggs decline with age. Starting in puberty, one egg matures and is released into the fallopian tube each month. This process is called ovulation. Every egg is enclosed in a tiny sac called a follicle. Many follicles begin to develop but only one egg will fully mature and ovulate. About two weeks after menstruation, a signal is sent to the mature follicle to open and release the egg. What is left over from that follicle (called a corpus luteum) produces progesterone. This hormone prepares the uterus for implantation of a fertilized egg. If a pregnancy does not occur, hormone levels fall and the next menstrual period begins.

How Sperm and Egg Meet

A sperm needs to fertilize an egg within 12-24 hours after ovulation for a pregnancy to occur. The sperm must travel up the cervix into the uterus into the fallopian tube to meet the egg. Millions of sperm are ejaculated and only a few hundred manage to reach the egg. Fertilization occurs inside the fallopian tube after a sperm penetrates the protective covering of the egg. The fertilized egg, now called an embryo, moves from the tube into the uterus. About 7-10 days after fertilization, the embryo implants into the lining of the uterus.

Obstacles to Pregnancy


  • As a woman gets older, the quantity and quality of her eggs decline. This process starts around age 35 and rapidly increases after age 40.

Problems with Sperm

  • Suboptimal sperm counts can be attributed to various health factors. Even if the sperm count is normal, the sperm may not function properly or may not be fastidious enough to make it through a woman’s reproductive tract to fertilize the egg.

Problems with Ovulation

  • About 25% of infertile women have problems with ovulation. These problems can include the inability to produce a fully matured egg or failure to ovulate or release an egg from the ovary.

Problems with Fertilization

  • A blockage in the reproductive tract of the man or woman may prevent fertilization.

Problems with Implantation

  • An embryo may not be able to implant in the uterus because of problems with the uterine lining or shape of the uterus.

Lifestyle Factors

  • Smoking, alcohol and drugs can decrease the quality and quantity of eggs and sperm.
  • Weight problems can affect hormone levels thereby impairing ovulation.
  • Medications, supplements and herbal remedies can affect fertility. Be sure to inform your health care provider of any medications or other substances you take.
  • Chemical exposure can affect hormone levels.
  • Sexually transmitted diseases can cause scarring of the reproductive tract.
  • Excessive exercise can cause irregular menstrual cycles and a poor ovulatory pattern.
  • Testicular heat can cause decreased sperm production.
Contact Women's Health Care Waukesha 262-549-2229 for Infertility diagnosis and treatment options.