Kansas City University of Medicine and Bio-Sciences researchers measured the heartbeat of unborn babies while their moms were exercising.
They compared these results with pregnant women who do not exercise regularly.
Researchers found unborn babies exposed to exercise have more advanced nervous systems and their respiratory systems are more mature.
Experts say these findings suggest babies born to mothers who exercise will be healthier after they are born.
Pregnant moms should consult their doctors before starting an exercise routine.
Moderate exercise is the key -- pregnant women should always stay within their comfort zone where they can still hold a conversation.