Obstetrics Pg No 413 -407

Immune Hydrops Fetalis

• Occurs in Rh-negative pregnancies, often associated with low fetal hemoglobin.

Rh Negative Pregnancy

• Dose: 300 mcg of anti-D (Low dose).
• Neutralizes 30 mL of FMH/15 mL of fetal RBC.
• Does not cause hemolysis even on crossing placenta.

### Indirect Coombs Test (ICT)

• Used to determine if an Rh-negative pregnant woman is sensitized.
• Performed during the first antenatal care visit and repeated at 28 weeks.
• Blood sample taken from the mother.

Rh Unsensitized

• Antepartum prophylaxis: 300 µg/1500 IU of anti-D given.
• Remains negative.

Unsensitized Rh-negative Females

• Anti-D: To protect the current pregnancy.
• Delivery:
  • Time: 39-40 weeks.
  • Mode: Vaginal delivery.
  • Early cord clamping: To prevent sensitization during delivery.

Post Delivery

• If the newborn is Rh-positive, a direct Coombs test (DCT) is performed on the newborn's blood.
  • If negative, the mother receives 300 µg anti-D (postpartum prophylaxis).
• If the newborn is Rh-negative, postpartum prophylaxis is not required.

Postpartum Prophylaxis

• Indication: Rh-positive newborn + DCT-negative.
• Aim: To protect the next pregnancy.
• Ideal time: Within 72 hours of vaginal delivery/C-section (can be given up to 28 days).
• Anti-D: Given even if postpartum sterilization is to be done.

Management of Rh-negative Sensitized Pregnancy

• Check Antibody Titre: To determine if anti-D antibodies are present in sufficient amounts to cross the placenta and cause hemolysis.
  • Critical Titre: 1:16 (mother's blood is serially diluted). If antibodies are present at ≥ 1:16, it is considered significant.
  • Maternal Antibody Titre is used to guide management.

Cordocentesis (Blood from umbilical cord)

• Hb of fetus < 2 SD or Hematocrit < 30%:
  • Mild anemia: Repeat Hb and hematocrit weekly, fetal surveillance from 32 weeks, delivery at 37-38 weeks.
• Hb of fetus ≥ 2 SD or Hematocrit ≥30%:
  • Severe anemia: If ≥ 35 weeks, delivery. If < 35 weeks: Intra-uterine blood transfusion.

Intrapartum Mx

• Mode of delivery: Vaginal delivery + delayed cord clamping if the mother is already sensitized.
• Cord clamping:
  • ICT status not measured:
    • Rh-negative, ICT-negative: Early cord clamping.
    • Rh-negative, ICT-positive: Delayed cord clamping.

Fetomaternal Hemorrhage & Other Indications of Anti-D

• FETOMATERNAL HEMORRHAGE (FMH)
  • Normal FMH: 30 mL (15 mL fetal RBC)
  • Kleihauer Betke test: Used to quantify FMH.

Anti-D Immunoglobulin

• Dose: 300 µg per 30 mL of FMH.

Tests

• Rosette test: A screening test for FMH.
• Kleihauer Betke test: A quantitative test to estimate the exact volume of FMH.
• Singer Alkali Denaturation test: A qualitative test to distinguish between vasa previa and placenta previa, and also helps detect FMH.

Other Indications for Anti-D

• First Trimester:
  • After abortion, ectopic pregnancy, molar pregnancy, chorionic villi sampling.
• Dosage (less than 12 weeks):
  • ACOG: 50 µg intramuscular.
  • RCOG: 300 µg intramuscular.
• Second/Third Trimester:
  • After amniocentesis, external cephalic/Internal podalic version, unexplained bleeding, antepartum hemorrhage, fetal death, abdominal trauma.
• Dosage (more than 12 weeks): 300 µg intramuscular.

Important Note

• Anti-D immunoglobulin has no role in cordocentesis when sensitization has already occurred (ICT+ve).
• Delivery should occur within 28 days of Anti-D administration.

Miscellaneous Topics

• Minor Antigens
  • High Risk of Sensitization: Kell, Kidd, Duffy-A.
  • No Risk of Sensitization: Lewis, 1-antigen, Duffy-B.

This quiz covers essential topics related to Rh-negative pregnancies, including immune hydrops fetalis, prophylaxis measures, and the roles of anti-D antibodies. Test your knowledge on the indirect and direct Coombs tests, and understand the management protocols for unsensitized Rh-negative females. Ensure you are well-informed on maternal-fetal Rh incompatibility issues.