A 25-year-old woman, gravida 2 para 1, comes to the office at 28 weeks gestation for her initial prenatal visit. She is known to be Rh(D)-negative, and her husband is Rh(D)-positive. Her previous pregnancy was uncomplicated, with no episodes of bleeding prior to delivery. The patient's labor was complicated by a significant intrapartum abruptio placentae, although she ultimately had a vaginal delivery. She received the same standard dose of anti-D immune globulin at 28 weeks gestation and immediately postpartum. She did not require a blood transfusion and recovered with iron supplementation. Prior to this visit, the patient came to the emergency department due to cramping without bleeding, and a transvaginal ultrasound at that time was consistent with 8 weeks gestation. Today, she has no vaginal bleeding, leakage of fluid, or contractions; fetal movements are occasional. She has no chronic medical problems and no surgical history. Temperature is 36.7 C (98 F), blood pressure is 100/70 mm Hg, and pulse is 80/min. Fundal height is 30 cm. Fetal heart rate is 145/min. Routine blood work shows that anti-D antibody titers are 1:32. Which is the most likely explanation for the positive antibody results in this patient?

Question

A 25-year-old woman, gravida 2 para 1, comes to the office at 28 weeks gestation for her initial prenatal visit.  She is known to be Rh(D)-negative, and her husband is Rh(D)-positive.  Her previous pregnancy was uncomplicated, with no episodes of bleeding prior to delivery.  The patient's labor was complicated by a significant intrapartum abruptio placentae, although she ultimately had a vaginal delivery.  She received the same standard dose of anti-D immune globulin at 28 weeks gestation and immediately postpartum.  She did not require a blood transfusion and recovered with iron supplementation.  Prior to this visit, the patient came to the emergency department due to cramping without bleeding, and a transvaginal ultrasound at that time was consistent with 8 weeks gestation.  Today, she has no vaginal bleeding, leakage of fluid, or contractions; fetal movements are occasional.  She has no chronic medical problems and no surgical history.  Temperature is 36.7 C (98 F), blood pressure is 100/70 mm Hg, and pulse is 80/min.  Fundal height is 30 cm.  Fetal heart rate is 145/min.  Routine blood work shows that anti-D antibody titers are 1:32.  Which is the most likely explanation for the positive antibody results in this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c19e_7347_8f63_1b8fae5170db_MD0005_00 An inadequate dose of anti-D immune globulin postpartum is the most likely cause of anti-D alloimmunization (eg, positive antibody screen) in this patient. Typically, a standard 300 µg anti-D immune globulin dose is administered at 28 weeks gestation and again <72 hours postpartum in an Rh(D)-negative mother with a Rh(D)-positive infant. However, pregnancies complicated by massive fetomaternal hemorrhage (eg, abruptio placentae) may require adjustments in the anti-D immune globulin dose, as the standard dose of anti-D immune globulin prevents maternal sensitization only up to 30 mL of fetal blood. In cases of fetomaternal hemorrhage, the amount of fetomaternal transfusion is calculated, so that an adequate dose of anti-D immune globulin can be administered within the 72-hour timeframe. The rosette test is a qualitative screening that determines the presence of fetomaternal hemorrhage. If negative, the standard dose of anti-D immune globulin is administered. If positive, the amount of hemorrhage can be determined using a Kleihauer-Betke test or flow cytometry, and the dose of anti-D immune globulin is increased based on the percentage of fetal red blood cells in the maternal circulation. Kleihauer-Betke test (Choice A) A standard dose of anti-D immune globulin is administered at 28 weeks gestation in uncomplicated pregnancies to neutralize occult fetomaternal hemorrhage. This patient's first pregnancy was uncomplicated at 28 weeks gestation and did not require an adjusted anti-D immune globulin dose. (Choice C) Early prophylaxis with anti-D immune globulin is indicated in patients with vaginal bleeding or trauma prior to 28 weeks gestation, conditions not seen in this patient. (Choice D) Prophylaxis between pregnancies is rarely indicated (eg, after accidental transfusion of Rh-positive blood). (Choice E) Delayed administration (eg, >72 hours postpartum), as opposed to early administration, of anti-D immune globulin postpartum may result in failure of effective anti-D immune globulin prophylaxis. Educational objective: Failure to adjust the dose of anti-D immune globulin after massive fetomaternal hemorrhage (eg, abruptio placentae) may result in maternal alloimmunization. References: Detection of fetomaternal hemorrhage. (http://www.ncbi.nlm.nih.gov/pubmed/22231030)

A 25-Year-Old Woman, Gravida 2 Para 1, Comes to the Office