Infertility Causes - Overview

Infertility - An Overview

Infertility affects about 6.1 million people in the United States, which is approximately 10% of the reproductive age population. Infertility is very common in males with male factor infertilitybeing present in up to half of all infertile couples.
At birth a women will have 2,000,000 to 4,000,000 oocytes (eggs), which is her lifetime supply. As a woman ages, the number of oocytes deteriorates to 200,000 to 400,000 by the time she begins menses leading to age related infertility. During her lifetime, approximately 300,000 to 400,000 eggs will be ovulated and as she ages the “quality” of her eggs declines.

Conception is a complicated process involving many biological processes in both partners. The male needs to produce healthy sperm that can reach and fertilize an egg (s) and the female needs to recruit and ovulate healthy eggs. Once the pregnancy is established, she must be able to carry the baby to term without miscarriage.
The eggs must travel unimpeded through the fallopian tubes to the distal end where fertilization occurs. The egg must be penetrated by a single “genetically healthy” sperm, which initiates the process of fertilization. After fertilization, a series of cell divisions occurs to form the embryo and after approximately five days the embryo travels to the uterus where it will implant in the endometrium and continue its development. Disruption of any of these processes, or others, may result in infertility. Please see the page on "Infertility-Causes" for more information.

Infertility - Causes

There are several potential causes of infertility in the female and in the male. Given the high incidence of male infertility, a complete evaluation of the male should always be performed. This is true even if a fertility problem has already been identified in the female. Very often there is a combination of female and male infertility factors.
Causes of Infertility

The processes listed below must occur in order for a pregnancy to result.
1. The male must produce healthy sperm that can reach and fertilize an egg.
2. Tubal disease- the tubes must be open and free of obstructions that can be caused by endometriosis, scarring, infection, and other conditions. The eggs travel through the tubes from the ovaries to the uterus.
3. Ovulatory disease- healthy follicles must be recruited and mature eggs must be ovulated. These processes are controlled by hormonal interactions between the hypothalamus gland and the pituitary gland. FSH stimulates follicular development and a surge of luteinizing hormone (LH) stimulates ovulation.
4. Cervical disease- the cervical mucus must support and nourish the sperm and it must be free of antisperm antibodies.
5. Endometriosis- endometriosis can attach to, and penetrate, the reproductive organs including the tubes. It can cause blockage and other damage to these organs.
6. Uterine factor infertility - the uterus must be free of large obstructions such as polyps and fibroids.
7. The endometrium must thicken and develop to accept a developing embryo. Sometimes the endometrium does not develop appropriately and this is known as a “luteal phase” defect. The fertilized egg (embryo) must travel to, and implant in, the endometrium.
8. Female age / ovarian factor and infertility - as women age, their eggs loose the capacity to fertilize and develop.
9. The egg and sperm must combine to form a healthy embryo with a normal number of chromosomes.
10. The female must be healthy and capable of carrying a baby to term.
Abnormal processes, or diseases, effecting any one, or a combination, of these steps can lead to infertility. Typically, common causes include: 1) irregular or failed ovulation 2) hormonal imbalances
3) damaged or blocked fallopian tubes 3) poor cervical mucus 4) a deformed uterus or the presence of large polyps and/or fibroids. 5) genetic disease 6) immunological 7) significant endometriosis which can negatively effect many processes. 8) inadequate sperm ( poor quantity or quality) . Also, once the fetus begins development, the mother must be able to carry the baby to term. Spontaneous abortion is a major cause of infertility, which can have many causes but most often results from embryonic genetic abnormalities (i.e. wrong number of chromosomes).

We discuss all of these potential infertility causes on this, and other Web pages.