A 19-year-old woman, gravida 1 para 0, comes to the office at 28 weeks gestation for a routine prenatal visit. Her prenatal course was complicated by vaginal bleeding at 8 weeks gestation due to a subchorionic hematoma. At that time, laboratory evaluation in the emergency department showed that she was Rh(D) negative, and she received anti-D immune globulin. The vaginal bleeding resolved, and the patient has had no other problems during this pregnancy. She has no chronic medical problems or previous surgeries. The patient does not use tobacco, alcohol, or illicit drugs. Blood pressure is 110/70 mm Hg and heart rate is 80/min. Fundal height is 28 cm and fetal heart rate is 145/min. Laboratory evaluation today shows a negative anti-D antibody screen. The patient is no longer in contact with the father of her child, and his Rh(D) status is unknown. Which of the following is the best next step concerning Rh(D) alloimmunization in this patient?

Question

A 19-year-old woman, gravida 1 para 0, comes to the office at 28 weeks gestation for a routine prenatal visit.  Her prenatal course was complicated by vaginal bleeding at 8 weeks gestation due to a subchorionic hematoma.  At that time, laboratory evaluation in the emergency department showed that she was Rh(D) negative, and she received anti-D immune globulin.  The vaginal bleeding resolved, and the patient has had no other problems during this pregnancy.  She has no chronic medical problems or previous surgeries.  The patient does not use tobacco, alcohol, or illicit drugs.  Blood pressure is 110/70 mm Hg and heart rate is 80/min.  Fundal height is 28 cm and fetal heart rate is 145/min.  Laboratory evaluation today shows a negative anti-D antibody screen.  The patient is no longer in contact with the father of her child, and his Rh(D) status is unknown.  Which of the following is the best next step concerning Rh(D) alloimmunization in this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c19e_e878_8f63_f1da1bfb06b1_MD0005_00 Rh(D) alloimmunization occurs when an Rh(D)-negative mother develops antibodies against Rh(D) antigen. Alloimmunization can lead to hemolytic disease of an Rh(D)-positive newborn and/or fetus; maternal IgG anti-D antibodies cross the placenta and destroy fetal red blood cells. When severe anemia develops in the fetus, it can lead to heart failure and subsequent hydrops fetalis (eg, pleural or pericardial effusion, ascites). Rh(D) alloimmunization Therefore, antibody screening is performed in all pregnant women at the first prenatal visit and at 28 weeks gestation to identify antibodies that increase the risk of hemolytic disease (typically anti-D). Positive antibody screening indicates that alloimmunization has already occurred, and anti-D immune globulin is not administered. Negative anti-D antibody screening confirms a lack of antigen exposure and is an indication to proceed with anti-D immune globulin prophylaxis at 28 weeks gestation (Choice E). This prophylactic anti-D immune globulin neutralizes any occult Rh(D) antigen exposure that may occur between the third trimester and delivery. The postpartum dose of anti-D immune globulin, administered <72 hours after delivery, reduces the risk of alloimmunization from fetomaternal hemorrhage associated with delivery. The postpartum dose, with the addition of the antenatal dose at 28 weeks gestation, reduces the risk of alloimmunization to <1% (Choice B). (Choice C) Anti-D immune globulin has a short half-life, and the dose administered at 8 weeks gestation is no longer effective after 28 weeks gestation. Therefore, even when an early dose of anti-D immune globulin has been given, another dose is still indicated to protect against possible fetomaternal hemorrhage that may occur between 28 weeks gestation and delivery. (Choice D) Anti-D immune globulin is not required in patients with an Rh(D)-negative partner because there is no risk of Rh incompatibility; anti-D immune globulin should be given when paternal Rh(D) status is unknown. Educational objective: Anti-D immune globulin is administered at 28 weeks gestation to all Rh(D)-negative women with a negative anti-D antibody screen; a repeat dose is given <72 hours after delivery if the infant is Rh(D) positive. References: Appropriate provision of anti-D prophylaxis to RhD negative pregnant women: a scoping review. (http://www.ncbi.nlm.nih.gov/pubmed/25491600)

A 19-Year-Old Woman, Gravida 1 Para 0, Comes to the Office