30 weeks fetal movement suddenly less may be physiological phenomenon, fetal distress and other reasons. 1. Physiological phenomenon: fetal movement refers to fetal body movement, generally after 28 weeks of gestation, under the guidance of a doctor to count fetal movement, self-evaluation of intrauterine fetal status, the normal ≥ 10 times / 2 hours. When the fetal sleep cycle will appear in the fetal movement suddenly reduced performance, after appropriate stimulation can return to normal, this is a physiological phenomenon, do not need special treatment. 2. Fetal distress: When fetal distress occurs, it will also be manifested as a sudden decrease or disappearance of fetal movement, which can not be improved after treatment of oxygen intake, change of position and rehydration, etc. Combined with fetal heart rate monitoring, ultrasonography, fetal physiological and physical scores, and monitoring of umbilical cord blood flow, etc., can assist in the diagnosis, and the pregnancy needs to be terminated in time to ensure the safety of mothers and infants after adequate assessment. In clinical practice, when fetal movement suddenly decreases at 30 weeks of pregnancy, it is necessary to go to the hospital in order to find out the cause as soon as possible and actively deal with it.