Approximately 5 percent of infertility cases are unexplained; the source of the problem cannot be identified. However, with today's technology, diagnoses of unexplained infertility are declining.
Eighty-five to 90 percent of infertility cases are treated with medication or surgery. In vitro fertilization (IVF) and other types of assisted reproductive technologies (ART) — in which barriers to successful conception are overcome in the laboratory — account for only about 5 percent of infertility treatments.
Ovulation is a complicated balancing act between hormones communicated back and forth between a woman's brain and her ovaries. Ovulation problems occur due to a number of factors:
- the ovaries may no longer contain fertilizable eggs,
- ovulation is disrupted because of a breakdown in the hormonal communication cycle
- scar tissue prevents ovulation from occurring,
And age, indeed, is a major factor in fertility. A 15-year-old girl, for instance, has between a 40 and 50 percent chance per cycle of getting pregnant following intercourse. At age 25, her chances are 30 to 35 percent for pregnancy each month. After age 35, a woman's fertility rapidly declines. By age 43, she has relatively little fertility left because her ovaries now produce fewer viable eggs. Women between ages 40 and 45 have roughly a three percent chance or less per cycle of achieving pregnancy.
The quality of a woman's eggs is critical to her chances of becoming pregnant. Egg quality is particularly important when a couple is considering in vitro fertilization or other ART procedures. These procedures depend on the ovaries responding to stimulation by producing multiple, high-quality eggs. For women older than age 42, physicians may recommend donor egg as an alternative to IVF, for this reason.
While an older woman is more likely to have poorer egg quality than a younger one, the condition can also affect younger women. In women age 30 to 35 who have been diagnosed as infertile, an assessment of their egg quality will show that about 10 percent are so unlikely to get pregnant with their own eggs that the only recourse for pregnancy is donor egg. Poor egg quality is the issue for only about seven percent of women in their 20s who are infertile.