In this paper we present an autonomic cardiovascular model of a preterm infant of 28 weeks of gestation with a birth weight of 1000 g and a closed ductus arteriosus by the end of the first week, that is capable of describing the complex interactions between heart rate, blood pressure and respiration. The hemodynamic model consists of a pulsatile heart and several vascular compartments, and is regulated by a baroreflex control system. The model is relatively simple to allow for a mathematical analysis of the dynamics but sufficiently complex to provide a realistic representation of the underlying physiology. The model provides (beat-to-beat) values of R-R interval and blood pressure that resemble realistic signals of preterm infants. The model is validated with experimental data obtained in preterm infants.