Blood pressure regulation during and after exercise in pregnant women
In healthy pregnancy, blood pressure is typically decreased compared to the non-pregnant state. However, how blood pressure is controlled in reponse to everyday stressors is not well understood. The baroreflex is the body's major physiological mechanism that regulates blood pressure. This reflex senses beat-to-beat alterations in blood pressure and causes reciprocal changes in heart rate to bring blood pressure back to normal (e.g., a sudden drop in blood pressure results in a rapid increase in heart rate to maintain blood pressure). Previous research has shown that the sensivitiy of this reflex is reduced during pregnancy, and that its set-point is lower than normal. Under these circumstances, a drop in blood pressure may not be corrected appropriately and light-headednes or faiting may occur; both of which are more common in pregnanct compared to non-pregnant women. During exercise, this same reflex is reset in non-pregnant individuals to allow blood pressure to increase, promoting blood flow to working muscles. However, after exercise this reflex is rapidly reset downwards and blood pressure often falls such that light headedness or fainting may occur. According to health guidelines, all healthy pregnant women are encouraged to exercise during pregnancy. However, how blood pressure is controlled during and following exercise is unknown. In particular, falling of blood pressure after exercise, in combination with already low blood pressure and a blunted ability to correct changes in blood pressure may make pregnant women more suceptiple to light-headedness of fainting following exercise. This research will examine how blood presure is controlled (e.g., the sensitivity and resetting of the baroreflex) prior to, during and following exercise in pregnant women. A better understanding of the pregnant women's cardiovascular system's ability to maintain blood pressure during exercise, and its ability to stabilize blood pressure postexercise, will help guide physical activity and recovery recommendations for pregnant women.