The pregnancy cycle is based on 4 weeks as 1 month, so 16 weeks of pregnancy is 4 months, which is the middle of pregnancy. A woman’s pregnancy lasts 40 weeks or 280 days from the first day of her last menstrual period, and based on 4 weeks as 1 month, the pregnancy period is 10 months. At 16 weeks of gestation, the fetus is 4 months pregnant. At this time, the fetus is about 16 cm long, weighs about 110 g and has a top-rump length of 12 cm. The sex of the fetus can be identified from the external genitalia, and the fetus has hair on its scalp and begins to show breathing movements. However, the fetal skin is very thin, dark red in color and without subcutaneous fat. Some pregnant women can feel the fetal movement, the pregnancy reaction is reduced and the appetite is increased. After 16 weeks of pregnancy, pregnant women should have regular prenatal checkups, visit the hospital to build a file, do Down’s syndrome screening and make an appointment for 4D ultrasound. In daily life, pregnant women are advised to start taking calcium and iron supplements and consume a diet rich in protein and vitamins to promote the growth and development of the fetus, but they need to be careful to avoid overeating and keep a happy mood.