A recent study is countering the mainstream thought that marriages with first cousins lead to birth defects.  Columbia University found that the risk of birth defects as a result of marriages between first cousins is no greater than that by women over that age of 40.  The research also found that first cousins share about 12.5 percent of the same DNA. Second cousins share just over six percent of their DNA and third cousins share about three percent.

Professor Diane Paul of the University of Massachusetts said women in their forties are not made to feel guilty about having babies and the same should apply to cousins who want to marry. Professor Hamish Spencer of the University of Otago in Dunedin, New Zealand noted that women over the age of 40 have a similar risk of having children with birth defects and no one is suggesting they should be prevented from reproducing. READ MORE