A 28-year-old primigravida with Rh-negative blood group is at 28 weeks gestation. Regarding prevention of Rh isoimmunisation, all of the following statements are TRUE EXCEPT:

Question

Accepted Answer

B. Anti-D immunoglobulin is contraindicated in the first trimester because it causes teratogenicity and increases the risk of congenital anomalies. ## Rh Isoimmunisation Prevention: Antenatal & Postnatal Prophylaxis

### Key Principles of Anti-D Administration

**Key Point:** Anti-D immunoglobulin (human) is safe throughout pregnancy and is NOT teratogenic — it does not cause congenital anomalies and is not contraindicated in the first trimester.

**High-Yield:** The standard dosing schedule for anti-D prophylaxis in non-sensitised Rh-negative mothers:
- **28 weeks gestation:** 100 IU/kg IM (or 500 IU in the UK regimen)
- **34 weeks gestation:** 100 IU/kg IM (if two-dose regimen used)
- **Postpartum:** 500 IU/kg IM within 72 hours of delivery (if baby is Rh-positive or group unknown)

### Fetal-Maternal Haemorrhage Assessment

**Clinical Pearl:** After delivery, the Kleihauer-Betke test (or flow cytometry) quantifies fetal red cells in maternal circulation to detect excessive fetomaternal haemorrhage (FMH). If FMH exceeds 4 mL fetal red cells (8 mL fetal blood), additional anti-D is required: 100 IU per mL of fetal red cells.

### Safety Profile of Anti-D

**Key Point:** Anti-D immunoglobulin is a blood product derived from human plasma and is safe in all trimesters. It:
- Does NOT cross the placenta in significant amounts
- Does NOT cause teratogenicity
- Is NOT contraindicated in pregnancy
- Is indicated even in early pregnancy after sensitising events (miscarriage, termination, ectopic pregnancy, molar pregnancy)

### Sensitising Events Requiring Anti-D Prophylaxis

| Event | Gestation | Anti-D Dose |
|-------|-----------|-------------|
| Spontaneous/induced abortion | Any | 100 IU/kg (minimum 500 IU) |
| Ectopic pregnancy | Any | 100 IU/kg |
| Molar pregnancy | Any | 100 IU/kg |
| Amniocentesis/CVS | Any | 100 IU/kg |
| External cephalic version | Any | 100 IU/kg |
| Antepartum haemorrhage | Any | 100 IU/kg |
| Fetal death | Any | 100 IU/kg |

**Warning:** The misconception that anti-D is teratogenic or contraindicated in early pregnancy is a common trap — this is FALSE and dangerous, as withholding anti-D in the first trimester after a sensitising event increases the risk of isoimmunisation.

Answer

A. A Kleihauer-Betke test or flow cytometry should be performed after delivery to quantify fetal-maternal haemorrhage and determine the need for additional anti-D

Answer

C. Anti-D immunoglobulin 500 IU/kg body weight should be administered within 72 hours of delivery if the baby is Rh-positive or blood group unknown

Answer

D. Anti-D prophylaxis at 28 weeks gestation requires 100 IU/kg body weight intramuscularly in a non-sensitised mother

A 28-year-old primigravida with Rh-negative blood group is at 28 weeks gestation. Regarding prevention of Rh isoimmunisation, all of the following statements are TRUE EXCEPT:

Explanation

Practice similar questions