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Nursing QUESTION #9136
Question 1
A 28-year-old woman at 12 weeks gestation is found to have blood group O Rh-negative with no antibodies. Her husband is Rh-positive. What is the MOST important preventive intervention during this pregnancy?
  • Administer Anti-D immunoglobulin 300 mcg IM at 28 weeks only
  • Administer Anti-D immunoglobulin at 28 weeks, and within 72 hours of any sensitizing event and after delivery✔️
  • No intervention needed as antibodies are absent currently
  • Monthly blood transfusion to maintain maternal iron levels
Correct Answer Explanation

Rhesus (Rh) Isoimmunization Prevention is critical in Rh-negative pregnant women:

Sensitizing events requiring Anti-D administration:

  • Amniocentesis, CVS, cordocentesis
  • Antepartum hemorrhage (APH)
  • External cephalic version (ECV)
  • Abdominal trauma
  • Miscarriage/termination
  • Ectopic pregnancy
  • Delivery (within 72 hours)

Routine prophylaxis: Anti-D 300 mcg IM at 28 weeks (and some protocols: 28 + 34 weeks).

Dose:

  • First trimester sensitizing event: \(250\,\text{IU}\) (50 mcg)
  • After 20 weeks / delivery: \(500\,\text{IU}\) (100 mcg) or \(300\,\text{mcg}\) (1500 IU)

The Kleihauer-Betke test estimates fetal-maternal hemorrhage volume to calculate additional Anti-D dose needed:

\[\text{Additional dose} = \frac{\% \text{fetal cells} \times \text{maternal blood volume}}{30} \times 300\,\mu\text{g}\]

Without prophylaxis, risk of sensitization after delivery = 16%. With Anti-D = reduced to <0.1%.