Millions of pregnant women worldwide could be spared the trauma of miscarriage and birth defects thanks to a ground-breaking Australian medical discovery.   Scientists have found simple vitamin B3 supplements could hold the key to prevention, after pin-pointing a molecule deficiency as the defect cause.   (Millions of pregnant women worldwide could be spared the trauma of miscarriage and birth defects thanks to a ground-breaking Australian medical discovery.   Scientists have found simple vitamin B3 supplements could hold the key to prevention, after pin-pointing a molecule deficiency as the defect cause.  )