Accuracy of prenatal determination of RhD type status by polymerase chain reaction (PCR) using fetal cells obtained at midtrimester amniocentesis in RhD-negative women: W. Sepulveda, A. Lighten,x T. Overton,x R.M. Warwick,x N.M. Fisk,x P.R. Bennett.x Royal Postgraduate Medical Schoo, Institute dof Obstetrics and Gynaecology, Queen Charlotte's and Chelsea Hospital, Goldhawk Road, London W6 0XG, United Kingdom