Free fetal DNA in maternal plasma was first described in 1997 and its discovery has revolutionised the field of non invasive diagnosis of fetal complications during pregnancy. It is clinically applied in the diagnosis of fetal Rhesus genotype in rhesus negative pregnant women. It has also been used for the early diagnosis of fetal sex and a number of single gene disorders. The use of free fetal DNA in placental related pregnancy complications is being explored.