Objective To search and review the best clinical evidence to direct the use of ultrasound. Methods After developing clinical questions, we searched the following databases for evidence: PROQUEST (1984 to 2004), SUMSEARCH (1980 to 2004) and The Cochrane Library (Issue 4, 2004). The key words were “repeated ultrasound exposure and children development (outcome)”. Results We found 3 systematic reviews, 3 randomized controlled trials, 1 cohort study and 1 case-control study. Most of the trials concluded that the effects of ultrasound to fetus were to be identified, some of the trials showed that ultrasound exposure could have an effect on fetus growth and language ability after delivery. Conclusions The pregnant women should avoid ultrasound as much as possible.