Rh Sensitization During Pregnancy

Rh sensitization can occur when a person with Reference Rh-negative blood Opens New Window is exposed to Rh-positive blood. During pregnancy, an Rh-negative woman can become sensitized if she is carrying an Rh-positive fetus.

Things that increase the risk of blood mixing and sensitization during pregnancy include:^{Reference 2}

• Delivery.
• Abdominal trauma, such as from a car accident.
• Abdominal surgery, such as a Reference cesarean section Opens New Window.
• Reference Placenta abruptio Opens New Window or Reference placenta previa Opens New Window, both of which can cause placental bleeding.
• Reference External cephalic version for a Reference breech Opens New Window fetus.
• Obstetric procedures such as Reference amniocentesis Opens New Window, fetal blood sampling, or Reference chorionic villus sampling (CVS) Opens New Window.
• Reference Miscarriage Opens New Window (spontaneous abortion), Reference ectopic pregnancy Opens New Window, or elective abortion (medical or surgical abortion) after 8 weeks of fetal age (when fetal blood cell production begins).
• Reference Partial molar pregnancy Opens New Window involving fetal growth beyond 8 weeks.

Although rare, Rh sensitization has been known to occur after needle sharing between intravenous drug users. Transfusing Rh-positive blood in an Rh-negative person can also trigger sensitization. But this is extremely rare because blood is always tested prior to transfusion.

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