The primary sign of pregnancy in humans is a missed period; however, there are often many other symptoms that accompany pregnancy, according to the National Institutes of Heath. Other symptoms include tender, swollen breasts, slight bleeding, fatigue, food aversions or cravings, headaches, nausea, vomiting, mood swings and frequent urination. Missing a period can be a sign of many conditions, but when combined with several pregnancy symptoms, pregnancy should be considered.
According to the National Institutes of Health, up to 25 percent of women experience some type of lighter than usual bleeding around the time of a missed period. Because of the timing, this is often mistaken for menstruation. Hormonal changes cause soreness, swelling, and tingling in the breasts of many women just one to two weeks after they become pregnant.
A woman's body is pumping more blood to carry nutrients to the fetus and she is producing more progesterone, causing intense fatigue that can strike within one week of pregnancy, according to the National Institutes of Health. The production of a hormone called human chorionic gonadotropin during the first few weeks of pregnancy increases the blood flow to the pelvis, and therefore increases the need to urinate more often. While commonly called 'morning sickness,' nausea and vomiting can occur at any time of day.