This objective of this chapter is to discuss fetal monitoring of the pregnant patient in the intensive care unit. Safety of the mother is of prime importance when a decision has to be made to choose between the mother and the unborn fetus. Management of these patients should include systemic assessment with an individual organ-based approach and special consideration to be given to gestational age of the fetus. Decision to continue pregnancy and mode of delivery would be based on viability of the fetus and FHR patterns observed in the ICU. Fetal oxygenation, physiological basis of fetal heart rate, maternal critical illness: impact on fetus, effects of drug intervention, effects of radiation, and fetal outcome in critically-ill pregnant patients are also discussed in this chapter.