What is the recommended Rhogam (Rho(D) immune globulin) schedule for preventing Rh sensitization during pregnancy?

Rhogam Schedule for Rh-Negative Pregnant Women

All Rh-negative, unsensitized pregnant women should receive RhIg 300 μg at 28 weeks gestation and again within 72 hours after delivery of an Rh-positive infant, which reduces alloimmunization rates from 1.8% to 0.1-0.2%. 1

Standard Antepartum and Postpartum Protocol

Routine Prophylaxis During Pregnancy

• Administer RhIg 300 μg (1500 IU) intramuscularly at 28 weeks gestation to all Rh-negative women when fetal blood type is unknown or Rh-positive 1, 2
• An alternative two-dose regimen of 100-120 μg at both 28 weeks and 34 weeks may be used, though the single 300 μg dose at 28 weeks is standard 3
• A repeat antepartum dose at 40 weeks is generally not required if the 28-week dose was given on schedule 3

Postpartum Administration

• Give RhIg 300 μg within 72 hours of delivery if the infant is confirmed Rh-positive 1, 2
• If RhIg is not given within 72 hours, administer as soon as recognized up to 28 days after delivery 3
• The postpartum dose may be withheld only if delivery occurs within 3 weeks of the last antenatal dose AND there is no excessive fetomaternal hemorrhage (>15 mL fetal RBCs) 2
• This two-dose protocol (antepartum plus postpartum) decreases alloimmunization from 13-17% down to 0.1-0.2% 1

Dosing for Pregnancy Complications and Events

First Trimester Events (<12 weeks)

• For spontaneous or induced abortion, ectopic pregnancy, or threatened abortion before 12 weeks: administer 50 μg (250 IU) within 72 hours 4, 1
• If the 50 μg dose is unavailable, use the standard 300 μg dose 1, 2
• Fetal RBCs display Rh antigens from as early as 6 weeks gestation, making sensitization possible even in very early pregnancy 1

Second and Third Trimester Events (≥12 weeks)

• For miscarriage, abortion, or ectopic pregnancy at or beyond 12 weeks: give 300 μg 2, 3
• For amniocentesis (at 15-18 weeks or third trimester): administer 300 μg 2, 3
• For chorionic villus sampling: give 120 μg before 12 weeks or 300 μg after 12 weeks 3
• For cordocentesis: administer 300 μg 3

Bleeding and Trauma

• For vaginal or placental bleeding at any gestational age: give RhIg to prevent alloimmunization 1
• For threatened abortion with heavy bleeding or abdominal pain, especially near 12 weeks: administer RhIg 1
• For abdominal trauma in second or third trimester: give 300 μg 2
• Consider RhIg for minor trauma, as 28% of pregnant patients with minor trauma demonstrate fetomaternal hemorrhage 1

Management of Large Fetomaternal Hemorrhage

When to Test for Excess Hemorrhage

• Consider quantitative testing (modified Kleihauer-Betke or flow cytometry) following events with potential placental trauma: placental abruption, significant abdominal trauma, external cephalic version, placenta previa with bleeding, or cordocentesis 3, 2

Additional Dosing Algorithm

• Standard 300 μg dose covers up to 15 mL of fetal RBCs (approximately 30 mL whole fetal blood) 2
• If fetomaternal hemorrhage exceeds 15 mL of fetal RBCs, calculate additional doses: divide the total volume of fetal RBCs by 15 mL to determine number of 300 μg doses needed 2
• If calculation results in a fraction, round up to the next whole number (e.g., if 1.4, give 2 doses) 2
• Alternatively, give an additional 10 μg for every 0.5 mL of fetal RBCs beyond the amount covered 3

Administration Guidelines

Route and Timing

• Administer intramuscularly, preferably in the deltoid muscle of the upper arm or lateral thigh 2
• Do NOT use the gluteal region due to risk of sciatic nerve injury 2
• Do NOT inject intravenously or into the neonate 2
• Optimal timing is within 72 hours of the sensitizing event, though some protection persists if given later 2

Multiple Dose Administration

• When multiple doses are required, the total volume may be divided and given at different sites simultaneously, or divided over intervals, provided the total is given within 72 hours 2

Essential Screening and Testing

Initial and Follow-up Testing

• Type and screen all pregnant women (Rh-negative or Rh-positive) at the first prenatal visit and again at 28 weeks 1, 3
• When paternity is certain, offer Rh testing of the father to Rh-negative women to potentially eliminate unnecessary RhIg administration 3
• Women with "weak D" (Du-positive) should NOT receive RhIg 3

Postpartum Confirmation

• Confirm infant's Rh status after delivery before administering postpartum dose 2
• The infant should have a negative direct antiglobulin test 2

Critical Considerations

Supply Shortages

• During RhIg shortages, prioritize postpartum patients and antenatal patients at later gestational ages 1
• If the typically used brand is unavailable, an equivalent RhIg product may be substituted 1

Common Pitfalls to Avoid

• Do not withhold RhIg based on early gestational age alone - fetal RBCs express Rh antigens from 6 weeks onward 1
• Do not assume low risk without evidence - while alloimmunization after first-trimester events is uncommon, existing data do not convincingly demonstrate safety of withholding RhIg 4, 1
• The consequences of alloimmunization are severe (fetal transfusion, hydrops, stillbirth, preterm delivery, hemolytic disease of newborn) and increase with each subsequent pregnancy 4

Informed Consent

• Obtain verbal or written informed consent prior to administering RhIg, as it is a blood product 3