**Question:** Best time to give Rh anti-D prophylaxis is:

A. immediately after delivery of the baby
B. during the first trimester of the next pregnancy
C. immediately after the first trimester ultrasound
D. just before the baby is born

**Correct Answer:** A. immediately after delivery of the baby

**Core Concept:** Rh anti-D prophylaxis is a preventive measure given to pregnant women who are Rh-negative to protect against Rh isoimmunization, a complication that can arise during pregnancy with an Rh-positive partner.

**Why the Correct Answer is Right:** Rh anti-D prophylaxis should be administered **immediately after delivery of the baby** because the primary goal is to prevent the mother's immune system from producing anti-D antibodies in response to Rh-positive fetal cells entering the maternal circulation during childbirth. If administered later, the antibodies may still form and lead to Rh isoimmunization, which can cause severe hemolysis in the next pregnancy.

**Why Each Wrong Option is Incorrect:**

A. **During the first trimester of the next pregnancy**: Administering anti-D prophylaxis too early can lead to false reassurance, as the antibodies may not develop in time to prevent Rh isoimmunization during childbirth.

B. **Just before the baby is born**: This timing is too late, as the antibodies may have already formed by the time of delivery, causing Rh isoimmunization.

C. **Immediately after the first trimester ultrasound**: The ultrasound assessment occurs too early, potentially leading to misguided decisions regarding the timing of anti-D prophylaxis administration.

**Clinical Pearl:** Timing is crucial when administering Rh anti-D prophylaxis. Misjudging the timing can result in ineffective prevention of Rh isoimmunization and subsequent complications in future pregnancies. In summary, administering prophylactic anti-D immediately after delivery of the baby is the optimal timing for effective prevention.