What is the recommended dose of Rhogam (Rho(D) immune globulin) in early pregnancy?

Rhogam Dosing in Early Pregnancy

For early pregnancy events before 12 weeks' gestation, a microdose of 50 mcg (250 IU) of Rho(D) immune globulin is the recommended dose for Rh-negative women to prevent alloimmunization. 1, 2

Dosing Guidelines Based on Gestational Age

• Before 12 weeks' gestation:

  • 50 mcg (250 IU) microdose of Rho(D) immune globulin 1, 2, 3
  • Administered intramuscularly, preferably in the deltoid muscle or lateral thigh 2
  • Should NEVER be administered intravenously or to the neonate 2

• At or after 13 weeks' gestation:

  • 300 mcg (1500 IU) full dose of Rho(D) immune globulin 2, 3

Administration Timing and Considerations

• Rho(D) immune globulin should be administered within 72 hours of the potentially sensitizing event (abortion, miscarriage, trauma) 2, 3
• If administration is delayed beyond 72 hours, it should still be given as soon as the need is recognized, for up to 28 days after the event 3
• If the full 300 mcg dose is unavailable for early pregnancy events, the microdose (50 mcg) is typically adequate 1

Special Circumstances

• Threatened abortion with continuing pregnancy:

  • A full dose (300 mcg) is recommended if pregnancy continues 2
  • Consider administration when there is "heavy" bleeding, associated abdominal pain, or when the event occurs near 12 weeks' gestation 4

• Ectopic pregnancy:

  • Before 12 weeks: 50 mcg (250 IU) microdose 3
  • After 12 weeks: 300 mcg (1500 IU) full dose 3

• Suspected large fetomaternal hemorrhage:

  • If more than 15 mL of fetal red blood cells is suspected, additional dosing may be required 2
  • Testing for the volume of fetomaternal hemorrhage should be performed using an approved laboratory technique (e.g., modified Kleihauer-Betke acid elution stain) 2

Clinical Considerations

• Fetal red blood cells display RhD antigens from as early as 6 weeks of gestation, creating potential for maternal sensitization even in early pregnancy 1, 4
• Only unsensitized Rh-negative women (those with a negative antibody screen) are eligible for Rho(D) immune globulin 1
• Rh-positive women do not require Rho(D) immune globulin 1

Important Caveats

• The gluteal region should not be used as an injection site due to risk of injury to the sciatic nerve 2
• In cases of supply shortages, prioritize postpartum patients and antenatal patients at later gestational ages 1
• While some guidelines (Society of Family Planning, WHO) recommend against RhD testing and RhIg administration for spontaneous and induced abortion at <12 weeks' gestation, the Society for Maternal-Fetal Medicine (SMFM) and American College of Obstetricians and Gynecologists (ACOG) still recommend administration to prevent potential alloimmunization 4, 1
• The evidence supporting use in first trimester is limited but the theoretical risk and minimal harm from administration generally favors its use 5, 6