When is Rho(D) immune globulin (Rhogam) administered during pregnancy?

When to Administer Rhogam (Rho(D) Immune Globulin) in Pregnancy

Rh-negative pregnant women should receive RhIg at 28 weeks gestation and within 72 hours after delivery of an Rh-positive infant, with additional doses required for any potentially sensitizing event throughout pregnancy. 1

Standard Prophylaxis Protocol

Routine Antenatal Administration

• Administer 300 mcg (1500 IU) RhIg at 28 weeks gestation to all unsensitized Rh-negative women when fetal blood type is unknown or known to be Rh-positive 1, 2
• Alternative dosing: 100-120 mcg at both 28 weeks and 34 weeks gestation 3
• This two-dose protocol reduces alloimmunization rates from 1.8% to 0.1-0.2% 1

Postpartum Administration

• Give 300 mcg RhIg within 72 hours of delivery if the infant is Rh-positive 1, 2
• If not given within 72 hours, administer as soon as recognized up to 28 days after delivery 3
• Postpartum RhIg alone reduces alloimmunization from 13-17% to 1-2% 1
• If delivery occurs within 3 weeks of the last antenatal dose, postpartum dose may be withheld unless fetomaternal hemorrhage exceeds 15 mL of fetal red blood cells 2

Pregnancy Complications Requiring RhIg

Early Pregnancy Loss (<12 weeks)

• Administer 50 mcg (minimum dose) within 72 hours for spontaneous or induced abortion, miscarriage, or ectopic pregnancy 1, 4
• If 50 mcg dose unavailable, use standard 300 mcg dose 1
• Fetal RBCs display Rh antigens from as early as 6 weeks gestation, making sensitization possible even in early pregnancy 1, 4

Late First Trimester and Beyond (≥12 weeks)

• Give 300 mcg RhIg for miscarriage, abortion, or ectopic pregnancy at or beyond 13 weeks 2, 3
• For molar pregnancy, administer RhIg unless complete mole is certain 3

Bleeding Episodes

• Administer RhIg for any placental or vaginal bleeding at any gestational age in unsensitized Rh-negative women 1
• For threatened abortion with heavy bleeding, abdominal pain, or events near 12 weeks, give RhIg 1
• Dose: 50 mcg before 12 weeks, 300 mcg at or after 12 weeks 1

Invasive Procedures

• Amniocentesis (15-18 weeks or third trimester): 300 mcg RhIg 2, 3
• Chorionic villus sampling: 120 mcg before 12 weeks, 300 mcg after 12 weeks 3
• Cordocentesis: 300 mcg RhIg 3
• External cephalic version: 300 mcg RhIg 3

Trauma and High-Risk Events

• Give 300 mcg RhIg for abdominal trauma in second or third trimester, as 28% of pregnant patients with minor trauma have fetomaternal hemorrhage 1
• Consider for placental abruption, placenta previa with bleeding, or any event with potential placental trauma 3
• Perform quantitative fetomaternal hemorrhage testing for these high-risk events to determine if additional doses needed 1, 3

Dosing Adjustments for Large Fetomaternal Hemorrhage

• Standard 300 mcg dose covers up to 15 mL of fetal red blood cells (30 mL whole blood) 2
• If fetomaternal hemorrhage exceeds 15 mL of fetal RBCs: divide the volume by 15 mL to calculate number of 300 mcg doses needed 2
• Give additional 10 mcg for every 0.5 mL of fetal red blood cells beyond the amount covered 3
• If calculation results in a fraction, round up to next whole number of doses 2

Critical Timing Considerations

• Optimal window: within 72 hours of any potentially sensitizing event 1, 2
• If multiple events occur requiring RhIg at 13-18 weeks, give another full dose at 26-28 weeks 2
• Repeat antenatal dose generally not required at 40 weeks if given at 28 weeks 3
• IgG half-life is 23-26 days; maintain adequate anti-D levels throughout pregnancy 2

Important Caveats

• Never administer RhIg intravenously (for IM preparations) or to the neonate 2
• Women with "weak D" (Du-positive) should NOT receive anti-D 3
• Women with molecularly defined weak D types 1,2,3,4.0,4.1, or Asian-type DEL do not require RhIg 5
• Obtain verbal or written informed consent before administration 3
• During supply shortages, prioritize postpartum patients and those at later gestational ages 1