10% of American couples 10 percent 10 percent one out of every six couples American Pregnancy Association one out of every six couples synthetic folic acids one out of every six couples About one in 10 couples 10 percent one out of every six couples American Pregnancy Association 6 million 6.1 million couples 10 percent 10 percent 10 percent six million American couples 10 percent fertility supplement on the market 10 percent one out of every six couples 6.1 million American couples