Wake Forest School of Medicine researchers studied 855 Hispanic women in Chicago, Miami, San Diego, and New York, and found that those who had more than four children were three times more likely to have a heart problem that could result in heart failure compared with childless peers, LiveScience reports. 
 

"During pregnancy, in order for a woman to support a fetus, her cardiovascular system has to undergo immense adaptations," said s researcher Shivani Aggarwal, M.D. Such changes include the thickening of the heart muscles, which can result in as much as a 50 percent increase in the heart's mass.
 

"All of this is thought to be reversible," Dr.Aggarwal noted, but studies have suggested that, in women who have been pregnant more times, the changes may persist after giving birth.
 

Among the study participants with five or more children, 85 percent had a heart function problem, called diastolic dysfunction, which is a decline in the heart's performance in the relaxation phase of the cardiac cycle. Among the women with two to four children, about 60 percent had diastolic dysfunction. Among women who didn't have children, 50 percent had diastolic dysfunction, which was unexpectedly high as well.