**2. Considerations**

Knowledge of the different characteristics of the animal and its gestation is a prerequisite in order to select the most suitable animal model, interpret experimental findings and reach appropriate translational conclusions. In obstetric research, in particular, it is necessary to consider fetal/neonatal characteristics and the physiological changes during the gestation period. Several species have been used to study the normal pregnancy and related pathological conditions [1]. First, the human gestation is described for comparison.
