At three weeks pregnant, your future baby is a microscopic cluster of rapidly dividing cells, reports the website BabyCenter. This group of cells, called a blastocyte, attaches itself to the lining of your uterus, where part of it begins to form the placenta, while the other part begins to form the fetus. At this early stage, even a blood test may not definitely reveal whether or not you are pregnant, but certain physical symptoms may hint at your condition. Interpret symptoms with caution, however. Pregnancy and premenstrual symptoms are often very much alike.
Implantation Bleeding
Implantation bleeding is the light spotting that may occur when the fertilized egg implants into the uterine lining. The spotting is usually pink or reddish-brown in color and occurs between six to 12 days after the egg is fertilized. It may be accompanied by slight cramping, but no intense or prolonged pain. According to the website BabyMed, only about a third of all women experience implantation bleeding.
Breast Changes
At three weeks pregnant, a rise in the hormones estrogen and progesterone can cause breasts to become swollen or extremely sensitive to the touch---even the pressure of a bra or wearing a shirt can cause mild to intense discomfort, states the American Pregnancy Association. In addition, some women find that their nipples become tender or tingly and that their areolas grow dark.
Nausea
Nausea or "morning sickness" is the classic sign of pregnancy. It may occur as early as the third week of pregnancy, although according to BabyCenter, most women don't begin to experience it until the sixth or seventh week, if at all. When nausea does occur, it is caused by surges and changes in the woman's hormone levels. Levels of nausea vary from woman to woman: Some women feel ill only in the mornings; others only when they haven't eaten; still others feel sick all day long.
Fatigue
Fatigue is a very common sign of early pregnancy. This symptom is believed to be caused by a surge in the hormone progesterone, notes the American Pregnancy Association. A woman only three weeks pregnant may suddenly find herself growing tired much earlier than usual, feeling exhausted after doing an activity that is usually effortless or fighting the urge to take a nap in the middle of the day.
