A fetal monitoring device developed for non-stress-test (NST) screening at home works on battery power, and is so small and lightweight (152 x 120 x 64 mm, 600 g) that a pregnant woman can monitor fetal Doppler ultra-sound and record fetal heart rate (FHR) and uterine contraction (UC) data on an attached memory IC card at any time and in any place away from a hospital. The physician can evaluate these data, transmitted via public telephone lines, using a built-in modem in the monitor. The combination of the memory IC card as a temporary storage device with the intermittent data transmission to the host provides endless data storage. The input-output relationship of the device was quantitatively evaluated using a Doppler ultrasound heart rate simulator. Forty pregnant women participated in an evaluation of this system. The total number of NST data transmissions was 648, and the total amount of data received was more than 6.7 Mbytes. Of the 648 transmissions, 475 were adequate for clinical interpretation. Of the 101 failed NST data transmissions, 85 resulted from patient handling errors. However, 82.4% of these errors resulted in reexamination and transfer of new data by the patients, who were aware of the insufficiency of the original data. The main cause of the noise in the data was zero-count data; this noise rate accounted for 4.1% of the data abnormalities. A questionnaire survey found that 96% of the participants wanted to use the monitor again in their next pregnancies, and 83% would recommend its use to pregnant friends. The system was easily used and accepted by pregnant women, and the NST data obtained were sufficient for clinical interpretation.