Anti-D Rh immunoglobulin is indicated in which of the following situations?

Question

Accepted Answer

Rh positive father, Rh negative mother. **Explanation:**

The primary objective of administering **Anti-D Rh immunoglobulin** is to prevent **Rh isoimmunization** (Rh sensitization). This condition occurs when an Rh-negative mother is exposed to Rh-positive fetal red blood cells, leading to the production of maternal antibodies that can cause Hemolytic Disease of the Fetus and Newborn (HDFN) in subsequent pregnancies.

**Why Option D is Correct:**
For Rh isoimmunization to occur, there must be **Rh feto-maternal incompatibility**. This is only possible if the **mother is Rh-negative** and the **father is Rh-positive**. If the father is Rh-positive, the fetus has a high probability (50-100%) of being Rh-positive. If fetal Rh-positive blood enters the maternal circulation (e.g., during delivery, miscarriage, or amniocentesis), the mother’s immune system recognizes the D-antigen as foreign and produces antibodies. Anti-D immunoglobulin neutralizes these fetal cells before sensitization occurs.

**Why Other Options are Incorrect:**
*   **Options A & B:** If the **mother is Rh-positive**, she already possesses the D-antigen. Her immune system will not produce antibodies against it; therefore, there is no risk of isoimmunization.
*   **Option C:** If **both parents are Rh-negative**, the fetus will inevitably be Rh-negative. Since there is no D-antigen present in either the mother or the fetus, no immune response can be triggered.

**High-Yield Clinical Pearls for NEET-PG:**
*   **Standard Dose:** 300 µg (1500 IU) is the standard dose, which can neutralize up to **30 ml** of fetal whole blood (or 15 ml of packed RBCs).
*   **Routine Timing:** In an unsensitized Rh-negative mother, Anti-D is typically given at **28 weeks** of gestation and again within **72 hours of delivery** (if the neonate is confirmed Rh-positive).
*   **Kleihauer-Betke Test:** Used to quantify the volume of feto-maternal hemorrhage to determine if additional doses of Anti-D are required.
*   **Indirect Coombs Test (ICT):** Must be **negative** in the mother before administering Anti-D; a positive ICT indicates that sensitization has already occurred, making Anti-D ineffective. [Practice more Obstetrics and Gynecology questions on OnCourse]

Obstetrics and Gynecology Questions

Topics

Prenatal Care

Labor and Delivery

Postpartum Care

Neonatology and Perinatology

Gynecological Disorders

Menstrual Disorders

Fertility and Infertility

Contraception and Family Planning

Menopause

Gynecologic Oncology

Urogynecology

Endocrinology of Pregnancy

Operative Obstetrics

Maternal-Fetal Medicine

Reproductive Endocrinology

Sexual Dysfunction

Pelvic Pain Syndromes

Gender-Affirming Care

Reproductive Ethics

About Obstetrics and Gynecology Questions