What is the management plan for a pregnant woman with Rh negative blood type?

Management of Rh Negative Pregnancy

All Rh-negative pregnant women should receive RhD immune globulin (RhIg) at 28 weeks gestation and within 72 hours after delivery of an Rh-positive infant, which reduces alloimmunization rates from 12-13% to 0.1-0.2% with the two-dose protocol. 1, 2, 3

Standard Prophylaxis Protocol

Routine Antenatal and Postpartum Administration

• Administer RhIg 300 μg at 28 weeks gestation to all unsensitized Rh-negative women when fetal blood type is unknown or known to be Rh-positive 1, 2, 4
• Administer RhIg 300 μg within 72 hours after delivery if the infant is Rh-positive 1, 2, 3
• If RhIg is not given within 72 hours, administer as soon as recognized up to 28 days post-delivery, as delayed administration still provides benefit 1, 4
• The two-dose protocol (antenatal + postpartum) is the gold standard, reducing alloimmunization from approximately 1.8% (with postpartum dose alone) to 0.1-0.2% 1, 2

Initial Prenatal Testing

• Type and screen all pregnant women at the first prenatal visit and again at 28 weeks with an indirect antiglobulin test 4
• Consider paternal Rh testing when paternity is certain to eliminate unnecessary RhIg administration if the father is Rh-negative 4
• Women with "weak D" (Du-positive) should NOT receive RhIg 4

RhIg Administration for Pregnancy Complications

First Trimester Events (Before 12 Weeks)

• Administer 50 μg RhIg within 72 hours for spontaneous abortion, induced abortion, threatened abortion with heavy bleeding/abdominal pain, or ectopic pregnancy 1, 3, 4, 5
• If 50 μg dose is unavailable, use the standard 300 μg dose 1
• Critical pitfall to avoid: Do not withhold RhIg based on early gestational age alone—fetal RBCs display D antigen from as early as 6 weeks gestation, making maternal sensitization possible even in very early pregnancy 1, 2
• Fetomaternal hemorrhage occurs in 48% of threatened abortions, 36% of complete abortions, and 22% of incomplete abortions 1

Second and Third Trimester Events (After 12 Weeks)

• Administer 300 μg RhIg within 72 hours for spontaneous or induced abortion, ectopic pregnancy, intrauterine fetal death, or molar pregnancy (unless complete mole is certain) 3, 4, 5
• For invasive procedures: amniocentesis, chorionic villus sampling (CVS), cordocentesis, or external cephalic version, administer 300 μg RhIg 4, 5
• For CVS specifically: 120 μg before 12 weeks, 300 μg after 12 weeks 4

Placental Trauma and Bleeding Events

• Administer RhIg for any placental or vaginal bleeding at any gestational age to prevent alloimmunization 1
• For events with significant placental trauma (placental abruption, blunt abdominal trauma, placenta previa with bleeding), administer 300 μg RhIg AND consider quantitative testing for fetomaternal hemorrhage 1, 4, 5
• Critical consideration: 28% of pregnant patients with minor trauma have fetomaternal hemorrhage 1
• If fetomaternal hemorrhage exceeds 15 mL of fetal RBCs (approximately 30 mL of whole fetal blood), administer additional RhIg at 10 μg per 0.5 mL of fetal RBCs 4, 5

Special Clinical Scenarios

Unknown Blood Type

• If blood type is unknown and testing is unavailable or would delay care (particularly for abortion), counsel the patient on risks but prioritize completing the procedure 1
• Administer RhIg if clinically indicated, as the risks of administration are minimal compared to potential sensitization consequences 1, 2

Determining Need for Postpartum RhIg

• Cell-free fetal DNA testing from maternal plasma can determine fetal RHD status with 97.2% sensitivity and 96.8% specificity, or exceeding 99% accuracy when performed after 11 weeks gestation 1
• This allows for targeted antenatal RhIg administration only when the fetus is Rh-positive 1

Repeat Antepartum Dosing

• A repeat antepartum dose at 40 weeks is generally not required if the initial dose was given at 28 weeks or later 4

Critical Timing and Dosing Summary

Clinical Scenario	Timing	Dose
Routine antenatal prophylaxis	28 weeks gestation	300 μg
Postpartum (Rh+ infant)	Within 72 hours of delivery	300 μg
First trimester events (<12 weeks)	Within 72 hours	50 μg (or 300 μg if unavailable)
Second/third trimester events (≥12 weeks)	Within 72 hours	300 μg
Invasive procedures	Within 72 hours	300 μg
Large fetomaternal hemorrhage	As soon as identified	Additional 10 μg per 0.5 mL fetal RBCs

Common Pitfalls to Avoid

• Do not assume early gestational age eliminates risk—fetal RBCs with D-antigen are present from 6 weeks onward 1, 2
• Do not withhold RhIg for "minimal" bleeding—even small amounts of fetomaternal hemorrhage can cause sensitization, and bleeding severity does not reliably predict hemorrhage volume 1
• Do not miss the 72-hour window without attempting late administration—RhIg given up to 28 days post-event still provides some benefit 1, 4
• Do not forget the postpartum dose if antenatal RhIg was given—both doses are essential for optimal protection 1, 2, 3
• Verify the infant's blood type before withholding postpartum RhIg—if unknown, assume Rh-positive and administer 3

Product Shortage Considerations

• 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

Informed Consent

• Verbal or written informed consent must be obtained prior to administration of RhIg, as it is a blood product 4