An unsensitized Rh-negative woman undergoes genetic amniocentesis at 17 weeks. The procedure is uncomplicated and the fetus is subsequently confirmed to be Rh-positive. What is the appropriate anti-D immunoglobulin dose for this sensitizing event?

• A No dose required because the gestation is below 28 weeks
• B 300 microgram intramuscularly as a single dose ✓
• C 100 microgram intramuscularly repeated weekly for 4 weeks
• D 50 microgram intramuscularly

Explanation

Amniocentesis, chorionic villus sampling, cordocentesis, and second or third trimester miscarriage all warrant a full standard prophylactic dose of 300 microgram anti-B regardless of gestational age, because fetomaternal haemorrhage volume cannot be predicted from gestation alone. The reduced 50 microgram dose applies only to first trimester events such as early miscarriage or termination below 12 weeks, which kills option D.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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