OBGYN BOARD REVIEW, Ob-Gyn Board Review Practice Questions, Obstetrics Practice Questions, Obstetrics Board Review, Obstetrics and Gynecology Board Review, Ob/Gyn Written Board Exam Practice Questions and Study Materials (Obstetrics and Gynecology)

Obstetrics and Gynecology Board Review Practice Questions
Book 1 - 2004
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QUESTION
A 25-year-old schoolteacher at 19-weeks estimated gestational age reports one of her students being diagnosed with fifths disease. Serum testing shows positive IgM titer and negative IgG titer.

The MOST appropriate action would be:

A) Vaccine for parvovirus B19
B) Oral immunoglobulin
C) Termination of pregnancy
D) Serial ultrasound evaluation
E) Amniocentesis for delta 450

ANSWER
D Serial ultrasound evaluation

This scenario is consistent with acute maternal infection with parvovirus B19 (Fifth disease). In this setting approximately 30% of fetuses will develop viremia. This viremia can subsequently lead to erythropoietic derangement and ultimately fetal hydrops secondary to severe anemia. Fetal loss rates vary from 2-10% with maternal infection so not all infected fetuses manifest severe anemia. Routine termination with documented infection is therefore unwarranted. Since this patient is already infected and has mounted a primary immune response, vaccination would not be of benefit (currently no vaccine is available for parvovirus B19). Immunoglobin therapy is not readily available and if it were it would be given parenterally to avoid GI breakdown.

Adverse fetal effects typically occur within 3-6 weeks of maternal infection. Serial ultrasound over this period to look for early signs of anemia (skin edema, organomegaly, effusions, ascites) is the recommended evaluation. If evidence of severe anemia is found, fetal survival can be markedly improved by intrauterine transfusion. Fetal survival of 60-80% is seen with transfusion while only 15-30% survive without treatment.

1. Murphy, J., Jones, D. Managing the Gravida with Parvovirus in OBG Management, Dowden, Volume 12, Nov. 2000:55-64

QUESTION
A patient with idiopathic thrombocytopenic purpura (ITP) is MOST likely to have which of the following laboratory abnormalities?

A) Decreased megalokaryocytes on bone marrow biopsy
B) Elevated partial thromboplastin time
C) Decreased percentage of large platelets on peripheral blood smear
D) Increased levels of platelet-associated immune globulin
E) Decreased hemoglobin levels

ANSWER
D Increased levels of platelet-associated immune globulin

ITP is an autoimmune phenomenon with increased platelet destruction due to the presence of anti-platelet antibodies. Patients with ITP are found to have high levels of either platelet-associated immune globulin, complement, or both. In addition to the presence of these antibodies, the diagnosis of ITP relies on meeting the following criteria:

normal blood count except for decreased platelets
normal bone marrow biopsy with normal or increased megalokaryocytes
increased percentage of large platelets on a peripheral smear
normal coagulation studies
no other obvious cause of thrombocytopenia

These criteria are easy to remember if one keeps in mind that ITP is a disease of platelet destruction, not of platelet production.

1. Kilpatrick SJ, Laros RK. Maternal hematologic disorders. Creasy RW, Resnik R.. Maternal-Fetal Medicine: Principles and Practice, 4th ed. WB Saunders & Co, Philadelphia, PA: 1999:935-963.

QUESTION
A 32-year-old, G2 P1, at 39-weeks estimated gestational age presents with abdominal pain and lack of fetal cardiac activity. She is type 0 negative and an indirect Coombs test is negative. A Kleihauer-Betke test gives an estimate of 25cc of fetal RBC (50cc fetal blood) being present.

How many standard vials of RhoGAM SHOULD be given in this setting?

A) 0
B) 1
C) 3
D) 5
E) 10

ANSWER
C 3

RhoGAM (immunoglobulin G towards Rh-D antigen) is very effective in preventing isoimmunization to Rh-D. Its exact mechanism of action is unknown but its use is based on the principle of passive immunity preventing an immune response. A standard dose is 300 ug/vial which provides protection against maternal exposure to up to 30cc of fetal Rh(+) blood, this is equivalent to 15cc of fetal RBC’s.

A Kleihauer-Betke test allows identification of the number of fetal cells present in a given volume of maternal blood. Calculation of the total amount of fetal cells present in the maternal system can then be performed. Following this calculation RhoGAM is administered by giving a standard vial for each 15cc of fetal RBC (30cc blood) plus one additional vial to ensure complete coverage in case of any misjudgment in calculation.

1. Cunningham, FG, et al. Diseases and Injuries of the Fetus and Newborn in Williams Obstetrics, 20th Edition, Appleton & Lange, 1997:982-991

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