The development of a portable electronic gestation calculator enables the obstetrician for the first time to recall all relevant data for his daily routine work from an electronic memory. This is useful not only for the calculation of the duration of pregnancies or the determination of delivery data, but also includes all relevant information from ultrasound biometry of the fetus. This paper presents the experience with this new electronic device, 'Babycomp', and comments on its design, technical features, functions and performance. The device has been thoroughly tested especially with respect to its suitability for practical purposes. Compared with the widely used disk for pregnancy calculations, the 'Babycomp' has a wide range of advantages for all users working in the field of obstetrics and reproductive medicine.