Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman. A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but can occur through assisted reproductive technology procedures. A pregnancy may end in a live birth, a spontaneous miscarriage, an induced abortion, or a stillbirth. Childbirth typically occurs around 40 weeks from the start of the last menstrual period (LMP). This is just over nine months (gestational age)—where each month averages 31 days. When using fertilization age it is about 38 weeks. An embryo is the developing offspring during the first eight weeks following fertilization, (ten weeks' gestational age) after which, the term "fetus" is used until birth. Signs and symptoms of early pregnancy may include missed periods, tender breasts, morning sickness (nausea and vomiting), hunger, and frequent urination. Pregnancy may be confirmed with a pregnancy test.