**Abstract**

The well-being of the fetus depends on the efficiency of its circulatory system and the proper maternal-fetal exchange. Hemodynamic changes can occur due to disturbance of fetal and maternal homeostasis, malformations, pregnancy pathology, and medications. Preterm labor directly affects maternal-fetal haemodynamics, both due to uterine contractions and medications used to inhibit it. Research on maternal-fetal haemodynamics in preterm labor is currently focused mainly on the safety of the used tocolytics. In this chapter, we will discuss the basic principles of fetal haemodynamics, ultrasound methods of maternal-fetal circulation assessment, and the influence of preterm labor on maternal-fetal haemodynamics, with particular emphasis on medications used in threatening and progressive preterm labor.

**Keywords:** preterm labor, maternal-fetal haemodynamics, doppler
