The objective of this study is to evaluate the performance of Sequenom's noninvasive test for fetal RHD genotype. The test uses MALDI-TOF mass spectrometry to detect DNA. The study is specifically designed to determine whether RHD typing using free fetal DNA in maternal circulation can accurately predict the neonatal RhD phenotype at birth.

In the United States and Canada, routine obstetrical care includes a blood test to determine the blood type of the mother (ABO and RhD). An antibody screen for anti-red cell antibodies in the mother's serum is also performed.

Postpartum prophylactic treatment of RhD negative women with anti-D immunoglobulin to prevent "RhD Disease", or hemolytic disease of the fetus/newborn, was initiated in the 1960's. In the mid 1980's, the routine administration of antenatal anti-D immunoglobulin became the standard of care as well. Although these treatments have dramatically reduced the incidence of RhD Disease, approximately 40% of all RhD negative pregnancies continue to receive unnecessary injections of antenatal anti-D immunoglobulin.

Genotyping platforms such as MALDI-TOF mass spectrometry allow for precise and sensitive detection of fetal-specific (paternally derived) alleles in maternal plasma. In this study, Sequenom's MassARRAY technology will be used to assess a noninvasive test for fetal RHD genotyping in a clinical setting.

Inclusion Criteria:

• Female at least 18 years of age
• RhD negative by serology
• Pregnant at no more than 11-13 weeks gestation confirmed by ultrasound
• Willing to provide signed and dated informed consent
• Able and willing to comply with the protocol

Exclusion Criteria:

• RhD negative women known to be alloimmunized to the RhD antigen

Pregnant women who are known to be serologically RhD negative.