Background: The cost-effectiveness ratio of routine ultrasound during pregnancy has been debated for years. However, there is a lack of population based data concerning both costs and benefit., Aim: Population based survey of ultrasound examinations (US) during pregnancy in Switzerland with respect to quantity, indications and results; estimation of total costs, the proportion paid by health insurance and the costs for routine US., Method: During a representative week all certified physicians and obstetrical out-patient departments in Switzerland were asked to participate in an anonymous questionnaire based national survey on the use of ultrasound during pregnancy., Results: With 62.9% of the physicians and 90.6% of the out-patient departments participating a total of 6455 questionnaires were returned. On average, 4.6 US were done per pregnancy or about 520,000 scans per year. At a mean price of $ 50 per scan total costs equalied $ 26 million a year. $ 19.5 million were covered by health insurance and the rest was not billed by the physicians. The indication for the scan was a medical problem in 48%, a routine scan in 36.9% of cases a first and a second trimester scan is paid for and in 15.1% reassurance of either the women or the physician. Abnormal results were found in 40.7% of medical indications, in 15% of routine scans and in 12.6% of reassurance cases., Conclusion: The considerable number of scans done for reasons of reassurance and not changed for does support our hypothesis that ultrasound during pregnancy has become a tool to routinely check the general state of the fetus comparable to the stethoscope of the general practitioner. One in seven US yielded a pathological result. Maximal cost savings for the health insurance amount to about 9 million a year. This amount has to be balanced by the health benefit, respectively if routine US were abolished.