Understanding Heart Rate Changes During Pregnancy: Impact on Fetus

Question
how does a increased heart rate effect the fetus?
what is the relation between mothers heart rate & the fetus?
how does a heart rate of 155 to 162 effect the unborn child?  

Answer
Diversion of blood flow to large muscles during physical exercise may decrease uteroplacental blood flow. The extent to which this may compromise the fetus is unknown. An additional load may be placed on the uteroplacental oxygen transfer mechanism, and this may cause an abnormal fetal heart rate pattern. Interpretation of these heart rate changes must take into account the stage of gestation. A normal fetus in a normal mother can probably tolerate mild to moderate exercise wthout difficulty. The effects of vigorous exercise on a normal infant are unknown. Therefore, the rise in heartbeat to 155 or 165 will not usually affect the fetus. It should not be harmful to the mother as well, as long as it returns to normal at rest.