Fertilization of the fertilized egg occurs as early as 7 days after conception, when the hormone levels in the pregnant woman’s body change and she may experience certain symptoms, such as increased appetite, drowsiness and fatigue. It takes about 1 week for the sperm and egg to unite to form a fertilized egg, which will be implanted in the endometrium. At this time, the concentration of chorionic gonadotropin in the body starts to rise, and the pregnant woman may experience some clinical symptoms such as heaviness in the breasts, enlargement and darkening of the nipples and areolas, and abdominal discomfort. In addition, the woman may experience nausea and slight vaginal bleeding when the fertilized egg is in the womb. As the concentration of chorionic gonadotropin in the body continues to rise, pregnant women may experience early pregnancy reactions such as nausea, vomiting, loss of appetite, aversion to greasy food, dizziness and weakness around 42 days after pregnancy. Therefore, if a woman has a delayed period for a week after sex, she should go to the obstetrics and gynecology department of the hospital to have blood or urine HCG and ultrasound tests to determine whether she is pregnant.