Show me the complete screening algorithm and management plan for rhesu

Show me the complete screening algorithm and management plan for rhesus negative mothers from booking visit

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Rh-Negative Mothers: Complete Screening Algorithm & Management Plan

Background: Why This Matters

The D antigen of the Rh blood group system is the primary cause of Rh incompatibility. An Rh-negative mother carrying an Rh-positive fetus can have fetal red cells cross the placenta into her circulation, triggering maternal IgG anti-D antibody formation. In subsequent pregnancies, these antibodies cross the placenta and destroy fetal red cells, causing hemolytic disease of the fetus and newborn (HDFN) — manifesting as erythroblastosis fetalis, hydrops fetalis, jaundice, and kernicterus.

First pregnancies are usually safe because the primary immune response generates IgM (which cannot cross the placenta). The danger escalates with subsequent pregnancies: ~3% of 2nd babies are affected, ~10% of 3rd babies, and rising thereafter. — Guyton and Hall Textbook of Medical Physiology

Pathogenesis of Rh sensitization and immune hydrops fetalis

Pathogenesis of immune hydrops fetalis — Robbins, Cotran & Kumar Pathologic Basis of Disease

Screening Algorithm from Booking Visit

STEP 1 — Booking Visit (First Antenatal Visit, ~8–12 weeks)

Action	Detail
Blood group & Rh typing	ABO and RhD status must be determined for ALL pregnant women
Indirect Coombs Test (ICT) / Antibody Screen	Test for pre-existing anti-D (or other) antibodies in maternal serum
Partner blood grouping	Determine if father is Rh-positive (if Rh-negative father → fetus must be Rh-negative → no risk)

Interpret the antibody screen:

Antibody screen NEGATIVE + Rh-negative → Unsensitized → proceed with prophylaxis protocol below
Antibody screen POSITIVE (anti-D detected) → Already sensitized → escalate to alloimmunized pregnancy management

STEP 2 — Antenatal Monitoring (Unsensitized Rh-Negative)

Timing	Action
~20 weeks	Repeat ICT/antibody screen
28 weeks	Repeat ICT — if still negative, administer routine antenatal anti-D prophylaxis
34–36 weeks	Repeat antibody screen before second dose (where two-dose regimen used)

STEP 3 — Routine Antenatal Anti-D Prophylaxis (RAADP)

Who: All unsensitized (antibody screen negative) Rh-D-negative pregnant women

Dose & Timing:

Standard regimen: Anti-D immunoglobulin 300 mcg IM at 28 weeks (single-dose protocol — ACOG-endorsed)
Alternative two-dose: 100–125 mcg at 28 weeks AND 34 weeks

The anti-D antibody is given antepartum at 28–30 weeks of gestation. The mechanism involves clearing Rh-positive fetal cells from maternal circulation before B-lymphocyte sensitization can occur — thereby preventing formation of memory B cells that would activate in future pregnancies. — Guyton and Hall Textbook of Medical Physiology

Rh(D) immune globulin (300 mcg IM) is a concentrated solution of human IgG with high-titer anti-Rh(D) antibodies. For this prophylaxis to succeed, the mother must be Rh-D-negative and not already immunized. — Katzung's Basic and Clinical Pharmacology, 16th Edition

STEP 4 — Sensitizing Events Requiring Additional Anti-D Doses

Anti-D must be given within 72 hours of any potential fetomaternal hemorrhage (FMH), regardless of gestational age:

Sensitizing Event	Anti-D Dose
Miscarriage / threatened miscarriage	50 mcg if <12 weeks; 300 mcg if ≥12 weeks
Ectopic pregnancy	50 mcg (<12 weeks); 300 mcg acceptable
Chorionic villus sampling (CVS)	300 mcg
Amniocentesis	300 mcg
External cephalic version (ECV)	300 mcg
Antepartum hemorrhage (APH)	300 mcg; repeat if continued bleeding
Abdominal trauma	300 mcg — "If as little as 0.1 μL of Rh-positive fetal blood enters an Rh-negative mother's circulation, the mother can develop Rh antibodies" — Tintinalli's Emergency Medicine
Intrauterine procedures	300 mcg
Delivery of Rh-positive baby	300 mcg within 72 hours of delivery

ACOG and ACEP both recommend 50 mcg for procedures/events before 12 weeks (due to small fetoplacental blood volume ~4.2 mL at 12 weeks); 300 mcg for events at ≥12 weeks. — Tintinalli's Emergency Medicine

Kleihauer-Betke (KB) test / Flow cytometry: Performed when large FMH is suspected (e.g., trauma, significant APH, abruption after 12 weeks). Quantifies fetal cells in maternal blood — additional anti-D vials are given if FMH exceeds the coverage of 300 mcg (~30 mL fetal whole blood).

STEP 5 — Postnatal Management

Neonatal result	Action
Baby Rh-positive, mother still unsensitized	Give anti-D 300 mcg IM within 72 hours of delivery
Baby Rh-negative	No anti-D required
Large FMH on KB test	Additional anti-D doses proportional to estimated hemorrhage

Management of the Sensitized (Alloimmunized) Rh-Negative Mother

When anti-D antibodies are already present at booking or develop during pregnancy, prophylaxis is futile and management shifts to fetal surveillance:

Monitoring Protocol for Alloimmunized Pregnancy

Anti-D Titer	Management
Low titre (<1:4–1:8)	Serial antibody titres every 4 weeks; fetal surveillance with growth scans
Rising titre (≥1:16 or critical titre)	Doppler assessment of fetal middle cerebral artery peak systolic velocity (MCA-PSV) every 1–2 weeks
MCA-PSV >1.5 MoM	Strongly predictive of fetal anemia → proceed to fetal blood sampling (FBS)

Fetal Blood Sampling (FBS) & Intrauterine Transfusion (IUT)

FBS via cordocentesis (umbilical vein) confirms fetal hemoglobin
If fetal Hb <2 SD below mean for gestational age → Intrauterine intravascular transfusion (IVT) with O-negative, CMV-negative, irradiated, leukodepleted blood
May be repeated every 2–4 weeks until fetus is mature enough for delivery

Delivery Timing

Unaffected or mildly affected fetuses: Deliver at 37–38 weeks
Severely affected or post-IUT: Deliver at 34–37 weeks depending on fetal condition
Post-delivery: neonatal exchange transfusion and/or phototherapy for jaundice/hyperbilirubinemia; monitor for kernicterus

Antenatal identification and management of the at-risk fetus have been greatly facilitated by amniocentesis and chorionic villus and fetal blood sampling. Severe intrauterine hemolysis may be treated by fetal intravascular transfusions via the umbilical cord and early delivery. — Robbins, Cotran & Kumar Pathologic Basis of Disease

Complete Algorithm Summary

BOOKING VISIT
    │
    ▼
Blood group + Rh typing + ICT (antibody screen)
    │
    ├─── Rh POSITIVE ──────────────────► Standard antenatal care
    │
    └─── Rh NEGATIVE
              │
              ├─── ICT POSITIVE (anti-D present)
              │         │
              │         └─► ALLOIMMUNIZED pathway:
              │              • Serial titres q4 weeks
              │              • MCA-PSV Doppler if titre ≥ critical level
              │              • FBS + IUT if MCA-PSV >1.5 MoM
              │              • Planned delivery 34–38 wks
              │
              └─── ICT NEGATIVE (unsensitized)
                        │
                        ▼
              Check partner Rh type
                        │
                        ├─ Partner Rh-NEGATIVE → Fetus must be Rh-negative
                        │                          → No anti-D needed; routine care
                        │
                        └─ Partner Rh-POSITIVE or unknown
                                   │
                                   ▼
                        PROPHYLAXIS PROTOCOL:
                        • Repeat ICT at 20 wks
                        • Anti-D 300 mcg IM at 28 wks (± 34 wks)
                        • Anti-D at ANY sensitizing event within 72 hrs
                        • Post-delivery: check baby's Rh type
                                   │
                                   ├─ Baby Rh-POSITIVE → Anti-D 300 mcg within 72 hrs
                                   │                      ± KB test if large FMH suspected
                                   └─ Baby Rh-NEGATIVE → No anti-D needed

Key Points to Remember

Point	Detail
Window for anti-D	Must be given within 72 hours of sensitizing event (ideally within 24 hrs)
First pregnancy risk	Usually safe — initial IgM response doesn't cross placenta; danger is in subsequent pregnancies
ABO protection	Concurrent ABO incompatibility partially protects the mother (fetal cells cleared by anti-A/B IgM before sensitization occurs)
Rh-negative = homozygous deletion	Rh-negative individuals lack the RHD gene entirely — so no "d" antibody exists
Weak D / partial D	Some women type as Rh-positive but have partial D antigens — may still be at risk; management is institution-specific
Non-D antigens	Anti-Kell (K), anti-c, anti-E can also cause HDFN — detected by ICT; managed similarly to anti-D alloimmunization

Sources:

Robbins, Cotran & Kumar Pathologic Basis of Disease — Immune Hydrops / Etiology & Pathogenesis
Guyton and Hall Textbook of Medical Physiology — Erythroblastosis Fetalis & Prevention
Katzung's Basic and Clinical Pharmacology, 16th Edition — Rh(D) Immune Globulin
Tintinalli's Emergency Medicine — Rh Seroconversion & Anti-D Indications
Emery's Elements of Medical Genetics and Genomics — Rhesus Hemolytic Disease of the Newborn

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