From the FDA Drug Label
For antenatal prophylaxis, one full dose syringe of HyperRHO S/D Full Dose (1500 IU; 300 mcg) is administered at approximately 28 weeks’ gestation. If pregnancy is terminated prior to 13 weeks’ gestation, where licensed, a single dose of HyperRHO® S/D Mini-Dose (250 IU; 50mcg) may be used instead of HyperRHO S/D Full Dose (1500 IU; 300 mcg) Following threatened abortion at any stage of gestation with continuation of pregnancy, it is recommended that a full dose of HyperRHO S/D Full Dose (1500 IU; 300 mcg) be given. Following miscarriage, abortion, or termination of ectopic pregnancy at or beyond 13 weeks’ gestation, it is recommended that a HyperRHO S/D Full Dose (1500 IU; 300 mcg) be given. If abdominal trauma, amniocentesis, or other adverse event requires the administration of HyperRHO S/D Full Dose (1500 IU; 300 mcg) at 13 to 18 weeks’ gestation, another full dose should be given at 26 to 28 weeks
The Rh immune globulin (RhIg) dose based on gestational age in weeks is as follows:
- Before 13 weeks: 250 IU (50 mcg) if pregnancy is terminated
- 13-18 weeks: 1500 IU (300 mcg) for events like abdominal trauma or amniocentesis, with another dose at 26-28 weeks
- 28 weeks: 1500 IU (300 mcg) for antenatal prophylaxis
- Beyond 28 weeks: 1500 IU (300 mcg) for events like miscarriage, abortion, or termination of ectopic pregnancy 1
From the Research
The standard dose of Rh immunoglobulin (RhIg) varies based on gestational age, with a dose of 50 mcg (250 IU) typically administered for pregnancies less than 12 weeks, and a full 300 mcg (1500 IU) dose recommended for pregnancies at or beyond 12 weeks, including postpartum administration, as stated in the most recent guideline 2. The administration of RhIg is crucial in preventing the development of antibodies that could harm future pregnancies in Rh-negative women who may be exposed to Rh-positive blood from their fetus. Key considerations for RhIg administration include:
- Gestational age: The dose of RhIg varies based on gestational age, with higher doses recommended for later pregnancy due to the increased potential volume of fetal-maternal hemorrhage.
- Sensitizing events: RhIg should be administered after potential sensitizing events, such as miscarriage, abortion, or trauma, to prevent the development of antibodies.
- Routine prophylaxis: RhIg should be administered at 28 weeks gestation for routine prophylaxis, and within 72 hours after delivery if the baby is Rh-positive.
- Additional doses: Additional doses of RhIg may be needed for significant bleeding events, with dosing calculated based on the estimated volume of fetal blood exposure. The most recent guideline 2 recommends a dose of 300 μg IM or IV for non-isoimmunized pregnant women, and emphasizes the importance of administering RhIg within the first 72 hours after a sensitizing event, or up to 4 weeks after the event if it was not given initially. It is essential to follow the recommended guidelines for RhIg administration to prevent Rh alloimmunization and ensure the best possible outcomes for Rh-negative women and their babies.