"Infertility" is a term that describes when a couple is unable to achieve pregnancy after 1 year of having regular, unprotected sex, or after 6 months if the woman is older than 35 years of age.
"Subfertility" is sometimes used to mean the same thing as infertility, but they are slightly different. Subfertility means that pregnancy is likely to occur without medical intervention, but it takes longer than usual.1
The term "infertility" also is used to describe the condition of women who are able to get pregnant but unable to carry a pregnancy to term because of miscarriage (sometimes called clinical spontaneous abortion), recurrent pregnancy loss, stillbirth, or other problems.2,3
Recurrent pregnancy loss is considered distinct from infertility. Although there may be some overlap, the causes of pregnancy loss, recurrent pregnancy loss, and stillbirth are often different from the causes of infertility.