Twenty-one weeks of pregnancy is the fifth month of pregnancy plus seven days. Seven days of pregnancy is a gestational week, 4 weeks for a gestational month, the whole pregnancy for 40 gestational weeks. The 21st week of pregnancy is the middle of pregnancy, the middle of pregnancy is the stage of fetal growth and development is relatively fast, pregnant women should not picky about food, diet should be diversified, but also meat and vegetables with a balanced nutrition in order to be conducive to the promotion of the growth and development of the fetus. Twenty-one weeks pregnant need to do urine routine, blood routine examination, need to measure the pregnant woman’s blood pressure and weight, measure the height of the bottom of the uterus of pregnant women and pregnant women’s abdominal circumference and the baby’s fetal heart rate and other checks. What’s more, it is necessary to do a good four-dimensional ultrasound examination, four-dimensional ultrasound is mainly to rule out the development of the fetus has deformities in the examination program. During pregnancy, you should follow the doctor’s instructions and do all the regular checkups during pregnancy. Only through good checkups can you understand the growth and development of the fetus and the specific conditions of the pregnant woman. If any abnormality is found during the checkup, appropriate treatment and conditioning measures should be taken in time to better protect the health of the pregnant woman and the safety of the fetus.