Objective:To determine whether diagnostic ultrasound wave irradiations do harm to the fetus of second trimester of pregnancy and to establish the safe threshold dose.Methods:18 pregnant cases were randomly divided into 4 groups:Ⅰ for control,Ⅱ,Ⅲ,Ⅳ were irradiated on the fetal kidney before artificial abortion for 5,10,30min respectively.All the samples were examined 48 hours later to observe the effects made on the ultrastructure of the fetal kidney.Results:group Ⅳ were found that irregular distribution of ...