This study evaluated women's understanding of prenatal ultrasound in terms of meeting the requirements for informed choice. A cross-sectional survey was conducted to evaluate (1) how information is provided, (2) women's perceived value of the information received and, (3) their understanding of ultrasound in relation to the principles of informed choice. Women (n=113) completed a questionnaire prior to their 18-week ultrasound. Fifty-five percent stated they received no information from their care provider. Only 31.9% considered health care providers as a "very helpful" source of information. Yet, 69.0% stated their care provider gave them information that facilitated their understanding. Gaps were identified in women's understanding of ultrasound. Specifically, 46.0% did not view ultrasound as a screen for anomalies; some were uncertain about their safety (18.6%), diagnostic capabilities (26.5%), and limitations of testing (37.2%). These results suggest that women's understanding of ultrasound does not meet the requirements of informed choice.