If you're trying to get pregnant and have a baby but it's not happening as quickly as you expected, you may wonder if you have a problem with fertility. Infertility is defined as not being able to get pregnant despite having frequent, unprotected sex for one year, or the inability to carry a pregnancy to live birth. Ten to 15 percent of couples in the United States are infertile. About 12 percent of American women have received infertility services in their lifetime. One in eight couples (or 12 percent of married women) have trouble getting pregnant or sustaining a pregnancy. About one-third of infertility is due to the female partner, one-third due to the male, and one-third caused by problems in both partners or is unexplained.