New knowledge is urgently needed in order to advise fit women in physically-active occupations (military service, police work, fire-fighting, competitive athletics) on safe intensities, durations and frequencies of physical exertion during a healthy pregnancy Recent studies from Dr. Wolfe's laboratory have examined cardiac autonomic function and acid-base regulation in fit, healthy women at rest and during exercise above and below the ventilatory anaerobic threshold (Tvent) in late gestation. Oxygen uptake kinetics in response to a step increase in work rate (80% Tvent) were also examined. Cardiac autonomic studies demonstrated that vagal/parasympathetic modulation is reduced at rest and sympatho-adrenal responses are attenuated during strenuous exercise above Tvent, resulting in a reduction in maximal heart rate reserve. Acid-base studies showed that pregnant women were able to maintain arterial pH values higher than those of non-pregnant controls at rest and during exercise at work rates above and below Tvent. Finally, the time constant for oxygen uptake kinetics was significantly slower in pregnant subjects compared to non-pregnant controls. Parallel studies from Dr. Mottola's lab have examined metabolic and cardiorespiratory responses to prolonged steady-state treadmill exercise in late gestation. Results showed that healthy, fit pregnant women exhibit transient post-exercise reductions in blood glucose, suggesting a temporary reduction in fetal glucose availability. Another study involving a case control design reported that exercise of 5 times or more per week increases the odds ratio of giving birth to a low birth weight baby, whereas an exercise frequency of 3–4 times per week does not affect birth outcome. In summary, information presented in this mini-symposium supports the hypothesis that healthy, fit pregnant women are well-adapted to perform acute bouts of high-intensity, short duration as well as prolonged exercise at moderate intensities. However, the use of proper warm-up and cool-down procedures and nutritional measures to prevent post-exercise in blood glucose levels are both recommended. Further study is needed to formulate evidence-based guidelines for prenatal exercise in this population.