Master the board step 3

Obstetrics
Third Trimester
A 38-year-old woman (G2 P1) is at 27 weeks’ gestation. She weighs 227 pounds.
She has gained 30 pounds during her pregnancy but reports that most of this is
“fluid retention.” She was diagnosed with gestational diabetes during her last
pregnancy. Which of the following is the next step in management?
a. Begin insulin therapy
b. Begin glipizide therapy
c. Obtain 1-hr 50 g OGTT
d. Obtain 3-hr 75 g OGTT
e. Obtain 3-hr 100 g OGTT
Answer: C. The first step in evaluating for gestational diabetes is with the 1 hr 50 g
OGTT in weeks 24–28. When this is positive, the patient must then undergo the confirmatory
3 h 100 g OGTT.
Screening Test Diagnostic Significance Next Step in Management
THIRD TRIMESTER ROUTINE TESTS
Diabetes
1 hr 50 g
OGTT given
between
weeks 24–28.
• Abnormal result:
1hr blood glucose > 140 mg/dL
• (+) screening: perform 3-hr
100 g OGTT (the definitive
test for glucose intolerance in
pregnancy). Requires overnight
fast.
Anemia
CBC
Measured at
weeks 24–28.
• Hemoglobin < 10 g/dL = anemia.
• The most common cause is iron
deficiency (even if not present in
1st trimester).
• Give iron supplementation for
iron deficiency.
Atypical
antibodies
Indirect
Coombs test
• Performed in Rh-negative women
to look for atypical antibodies
(anti-D Ab) before giving
RhoGAM.
• RhoGAM is not indicated in
Rh negative women who have
developed anti-D antibodies.
GBS screening
Vaginal and
rectal culture
for group B
streptococci
at 35–37
weeks
• (+) GBS is a high risk for sepsis in
newborn.
• Treat with intrapartum IV
antibiotics.
• Intrapartum antibiotic
– IV penicillin G
– IV clindamycin or erythromycin
in penicillin-allergic patient
GBS = Group B Streptococcus; IV = intravenous; OGTT = oral glucose tolerance test
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