Three weeks pregnant does not have the most obvious signs, usually the earliest symptom of pregnancy is menopause. The earliest symptom after pregnancy is the cessation of menstruation, three weeks pregnant in the clinic many pregnant women do not have other special symptoms, with the increase of pregnancy, some pregnant women will appear early pregnancy reaction, such as nausea, vomiting, do not think of food and so on, this is due to the rise in the level of progesterone in the body of the female after pregnancy, the gastrointestinal tract’s motility by the effect of progesterone has been weakened. With the increase of pregnancy, the breasts will also change, such as breast enlargement, nipple and areola color will deepen, which is to prepare for breastfeeding in the future. Moreover, many people experience easy sleepiness and drowsiness after pregnancy. In addition, some pregnant women may experience symptoms such as lumbago and lumbar pain due to the enlargement of the uterus after pregnancy. Clinically, if a woman experiences delayed menstruation and is unsure whether she is pregnant, it is recommended that she go to the hospital in time for a blood test for HCG or urine pregnancy test and ultrasound.