Kristensen SS, et al. - RhD negative mothers with an RhD positive fetus undergoing CVS or AC were examined for the risk of RhD immunization induction in pregnancies. Researchers conducted a registry based study in a Danish cohort of 10,085 women who have not been given rhesus prophylaxis. Of these, 9,353 had no invasive procedures performed, 189 had AC and 543 had CVS performed. Observations revealed a very low RhD immunization rate before gestational week 25-29 in RhD negative women carrying a RhD positive fetus, even in women undergoing prenatal invasive testing without rhesus prophylaxis.