Diagnostic ultrasound has been in use for over 50 years in Obstetrics and Gynecology. Its record of safety is excellent with no epidemiological studies demonstrating harmful effects in human fetuses. It needs to be remembered, however, that all epidemiological studies published so far are based on information obtained with pre-1992 machines, a time when acoustic output was allowed to be increased, for fetal use, from 94mW/cm2 to 720mW/cm2, a factor of almost 8. At the same time a new exposure parameter was introduced, the Output Display Standard, consisting of the thermal (TI) and the mechanical index (MI), because of the two major mechanisms by which ultrasound may affect insonated tissues. Furthermore, while B-mode, grey-scale continues to be the main examination mode, newer technologies and applications of these technologies have been introduced over the years. One, in particular needs to be attentively examined, in terms of bioeffects and safety to the fetus: spectral Doppler. Furthermore, many are advocate for early anatomy survey. Some promote spectral Doppler evaluation of the fetal heart in the first trimester for early assessment of cardiac function, as a diagnostic tool for cardiac abnormalities. The first issue to be considered is: is there enough evidence to validate the use of ultrasound in general and spectral Doppler in particular, in the first trimester? If the answer is positive, then the question needs to be asked: can ultrasound (including spectral Doppler) have detrimental effects on the fetus in the first trimester and, if yes, can a risk-benefit analysis allow us and the patients to make informed decisions?