Anatomical models of pregnant women are used in several applications, such as numerical dosimetry, to assess the potential effects of electromagnetic fields on biological tissues, or medical simulation. Recent advances in medical imaging have enabled the generation of realistic and detailed models of human beings. The construction of pregnant woman models remains a complex task, since it is not possible to acquire whole-body images. Only few models have been developed up to now, and they all present some limitations regarding the representation of anatomical variability of the fetus shape and position over the entire gestation. This paper describes a complete methodology that intends to automate each step of the construction of pregnant women models. The proposed approach relies on the segmentation of 3-D ultrasonic and 3-D magnetic resonance imaging (MRI) data, and on dedicated computer graphics tools. The lack of complete anatomical information for the mother in image data is compensated, in an original way, by merging the available information with a synthetic woman model, deformed to match the image-based information. A set of models anatomically validated by clinical experts is presented. They include detailed information on uterofetal units and cover different gestational stages with various fetal positions.