Pregnancy, also known as gestation, is the state of carrying a developing embryo or fetus within the female body.  After the egg is fertilized by a sperm and then implanted in the lining of the uterus, it develops into the placenta and embryo, and then into a fetus. Childbirth  usually occurs around 40 weeks or just over 9 months from the last menstrual period (LMP). Babies born before 39 weeks are considered early term while those before 37 weeks are premature birth. Symptoms of early pregnancy may include missed menstrual periods, tender breasts, nausea and vomiting, hunger, and frequent urination.