21 weeks the baby does not move much during the day can rest more, eat properly, ultrasound examination to understand the cause. 1. more rest: after pregnancy is generally around 16-20 weeks of fetal movement, 21 weeks of fetal movement time is relatively early, fetal movement may be relatively weak is not easy to be noticed by pregnant women, daytime life and work will be distracted by the feeling that the baby is not very active, at this time you can pay more attention to the bed rest, choose the left side of the lying position, meditate to feel the changes in the fetal movement. 2. Appropriate food: 21 weeks the baby is not very active during the day, you can eat some food, food in the gastrointestinal tract will be rapidly digested and absorbed, gastrointestinal peristalsis, the body metabolism speed up, the visceral blood circulation accelerated, the fetus has a sense of the number of fetal movement will increase. 3. ultrasound: 21 weeks baby daytime not much activity can go to the hospital to do ultrasound, to understand the development of the fetus in the womb, there is a lack of oxygen can be appropriate oxygen treatment. After pregnancy more observation of the body changes, there are abnormalities timely consultation.