[Medical Q&A] Why does morning sickness occur after pregnancy?

Planner: Chinese Medical Association

Reviewer: Zhao Jie, Chief Pharmacist Professor of the First Affiliated Hospital of Zhengzhou University

In movies and TV shows, we often see such a plot: nausea and vomiting during meals, suggesting that the characters are pregnant. This is a common symptom for many pregnant women in the early stages of pregnancy, and there are many reasons for morning sickness.

After a woman becomes pregnant, the hormone secretion in her body will change to stabilize the uterus and provide a favorable environment for fetal development. When the pregnancy is about 6 weeks, the chorionic gonadotropin in the pregnant mother's body will stimulate the vomiting center of the brain, so it is easier to feel nauseous during pregnancy than usual. In addition, a large amount of progesterone will be secreted in the pregnant woman's body, which will inhibit the movement of the stomach muscles, relax the cardia sphincter at the junction of the stomach and esophagus, reduce gastric acid secretion, prolong gastric emptying time, and slow down intestinal peristalsis, which will cause food to go down slowly and easily reflux into the esophagus. Some women will become more sensitive to smell after pregnancy, and certain smells (such as food, cigarettes, perfume, etc.) may induce nausea and vomiting. Generally speaking, the symptoms of morning sickness will gradually disappear after 12 weeks of pregnancy, and the appetite will gradually return to normal. Of course, a small number of pregnant mothers will continue to have nausea and vomiting throughout the pregnancy, and some may even develop into severe vomiting during pregnancy. If the morning sickness is not severe, no measures are needed; if the morning sickness is so severe that you cannot eat a single bite, and even vomit when you drink water, and you vomit more than 4 times a day, you need to seek medical attention promptly and receive treatment according to the doctor's advice, otherwise the normal development of the fetal brain will be affected due to insufficient energy intake.