An Rh-negative, previously unsensitized G2P1 woman undergoes suction evacuation for a missed miscarriage at 9 weeks of gestation. What is the recommended dose of anti-D immunoglobulin?

• A 150 microgram IM
• B 50 microgram IM ✓
• C 300 microgram IM
• D Anti-D is not required before 12 weeks

Explanation

For first-trimester abortions, ectopic pregnancies and chorionic villus sampling, fetomaternal hemorrhage is small and 50 micrograms of anti-D given intramuscularly is sufficient to cover up to about 5 mL of fetal blood. The 300 microgram dose used at 28 weeks and after delivery covers 30 mL of fetal whole blood, so option C overstates the need. Anti-D is still required even in early gestation because sensitization can occur with very small volumes of fetal cells.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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