There are several reasons for numbness in the hands of pregnant women during sleep: 1, poor blood flow, the blood viscosity of pregnant women is generally higher, relatively in a state of high coagulation, easy to circulate poorly, when sleeping muscles in a state of rest and reduced activity, can not promote blood flow through contraction, prone to numbness in the distal extremities, not only hand numbness will often cause numbness in the feet. 2, nerve damage, this nerve damage is functional The nerve damage is a functional ischemic, hypoxic injury, pregnant women because of the increase in the abdominal girth of the viscera have a certain compression effect, may cause a variety of nerve compression, especially the upper limb shoulder and lower limb hip nerve, up after the activity can often be improved. 3, diabetes, gestational diabetes can cause abnormal blood sugar, high blood sugar can damage the peripheral nerves, in the usual symptoms are not obvious, the symptoms are more likely to appear at night when the nerve blood supply is poor. This symptom is more likely to appear when the nerve blood supply is poor at night.