A Rh-negative woman at 14 weeks gestation presents with vaginal bleeding and clots. What Rhogam dose is indicated?

A Rh-negative woman at 14 weeks gestation presents with vaginal bleeding and clots. What Rhogam dose is indicated?

• A. 150 μg
• B. 300 μg
• C. 50 μg
• D. 600 μg

Answer: (B)

DosingRh immunoglobulin depends on how far along the pregnancy is and how much fetal blood could have leaked into the maternal circulation. In early pregnancy, smaller amounts are used, but once you reach the second trimester (after about 12 weeks) and especially with any vaginal bleeding, the standard prophylactic dose is higher to cover the typical amount of fetal red cells that might enter the mom’s blood. In a bleeding event at 14 weeks, the appropriate starting prophylaxis is a standard dose of 300 μg to prevent maternal sensitization to the D antigen. The other doses aren’t appropriate here: a smaller dose (like 50 μg) is used in very early pregnancy, and a dose of 600 μg would be reserved for larger fetomaternal hemorrhages as guided by testing (e.g., Kleihauer-Betke) to determine if more anti-D is needed. In this scenario, 300 μg is the correct choice to provide adequate protection against alloimmunization after a second-trimester bleed.

DosingRh immunoglobulin depends on how far along the pregnancy is and how much fetal blood could have leaked into the maternal circulation. In early pregnancy, smaller amounts are used, but once you reach the second trimester (after about 12 weeks) and especially with any vaginal bleeding, the standard prophylactic dose is higher to cover the typical amount of fetal red cells that might enter the mom’s blood. In a bleeding event at 14 weeks, the appropriate starting prophylaxis is a standard dose of 300 μg to prevent maternal sensitization to the D antigen.

The other doses aren’t appropriate here: a smaller dose (like 50 μg) is used in very early pregnancy, and a dose of 600 μg would be reserved for larger fetomaternal hemorrhages as guided by testing (e.g., Kleihauer-Betke) to determine if more anti-D is needed. In this scenario, 300 μg is the correct choice to provide adequate protection against alloimmunization after a second-trimester bleed.