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Question 748
Obstetric infection → Viral
Classification
Question
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Timing of amniocentesis after maternal chickenpox
Question Stem
A woman develops chickenpox during pregnancy and, following counselling, elects to undergo amniocentesis for VZV DNA PCR. Which condition should be satisfied before the procedure is performed?
Options
A
The maternal rash must have been present for less than 24 hours
B
Maternal VZV IgG must have become undetectable
C
The fetal ultrasound must be abnormal
D
The maternal skin lesions must have completely healed
E
Delivery must be planned within 7 days
Explanation
Women considering amniocentesis for VZV DNA PCR should be counselled regarding its risks and limitations. Amniocentesis should not be performed before the maternal skin lesions have completely healed. PCR has a strong negative predictive value but a poor positive predictive value for fetal damage, so a positive result does not by itself establish fetal varicella syndrome.
Option Validity
A) the procedure should not be undertaken during the early active-rash period.
B) disappearance of maternal VZV IgG is not a prerequisite for amniocentesis.
C) an abnormal ultrasound is not stated as a mandatory prerequisite for considering VZV PCR.
E) planned delivery timing is unrelated to the prerequisite for amniocentesis.
Further Reading
RCOG Green-top Guideline No. 13, Chickenpox in Pregnancy, section 6.2.