The Safe Use of Diagnostic Ultrasound in Obstetrics and Gynecology

The diagnostic ultrasound was considered safe after the intensity threshold was known and the output intensity (Ispta) was regulated to be less than 10 mW/cm2 in diagnostic devices in Japan, and diagnostic ultrasound was thought safe in USA when both thermal index (TI) and mechanical index were less than 1.0 in the obstetrical setting. Simple B-mode machine was not concerned from the thermal reason due to its extremely low ultrasound intensity, while the exposure was recommended within 30 minutes. Diagnostic ultrasound should be used after obstetrical setting in fetal study. The TI will be higher in febrile cases than nonfebrile, and the surface temperature of transvaginal scan (TVS) probe should be lower than 41oC. Simple three-dimensional or four-dimensional ultrasound imaging without pulsed Doppler studies will be as safe as Bmode when the study is within 30 minutes, because they are composed of simple B-mode images. The spectral Doppler study was not routinely used and its exposure should be short in 11 to 13 weeks of pregnancy in the statements of WFUMB and ISUOG, because experimentally early fetal animal tissue was sensitive to the studies. The use of diagnostic ultrasound should be limited for medical purposes, but not for the entertainment or keepsake of pregnancy.