Master the board step 3

Obstetrics
Screening Test Diagnostic Significance Next Step in Management
Infection: HIV ELISA • Confirm (+) ELISA screen with
Western blot test (presence of
HIV core and envelope antigens).
Infection:
Chlamydia/
Gonorrhea
Cervical culture
FIRST TRIMESTER OPTIONAL TESTS
• Gram stain
• Chlamydia and gonorrhea culture
• Also treat Trichomonas vaginalis
(can cause premature labor).
• Chlamydia trachomatis is an
obligate intracellular parasite: It
needs a host cell to survive.
• Neisseria gonorrhea is a gramnegative
diplococcus that grows
on chocolate agar. NAAT is the
test of choice.
Tuberculosis PPD • Test for exposure to TB in high
risk mothers.
Trisomy 21: Early
testing
β-hCG
Pregnancyassociated
plasma protein
A (PAPP-A)
Fetal nuchal
translucency
• (+) test is induration, not
erythema.
• Offered to high-risk pregnancies
(females above the age of 35 at
delivery, women with a history of
prior trisomy 21).
• Always get consent for HIV testing.
• All babies born to HIV (+) women
will be HIV antibody (+) (passive
transport of maternal Ab’s). (+)
Ab’s do not indicate infection in
infant.
• Antiretrovirals are not
contraindicated in pregnancy.
• See Perinatal Infections for further
treatment.
(+) Chlamydia/gonorrhea
• PO azithromycin + IM ceftriaxone
(treatment of choice)
• Alternative: PO amoxicillin
(+) Bacterial vaginitis
• PO metronidazole or clindamycin
PO
(+) Trichomonas vaginalis
• PO metronidazole
• (−) PPD: No further follow-up is
needed.
• (+) PPD: Order chest x-ray to rule
out active disease.
Treatment for positive screen:
• (+) PPD/ (−) CXR: INH and B6 for
9 months.
• (+) PPD/ (+) CXR (+) sputum:
Begin triple therapy
antituberculosis Rx if sputum
stain positive. Obtain sputum for
culture.
• Avoid streptomycin in pregnancy
because of the risk of ototoxicity
in the fetus.
• (+) screening test is confirmed
with chorionic villus sampling in
the first trimester.
MHATP: microhemagglutination assay for antibodies to T. pallidum; FTA: fluorescent treponema antibody absorption;
NAAT: nuclear acid amplification
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