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Question 18
Feto-maternal medicine → Perinatology
Classification
Question
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Timing of chorionic villus sampling
Question Stem
A pregnant woman at 9+5 weeks of gestation has an indication for definitive prenatal diagnosis and requests chorionic villus sampling as soon as possible. What is the most appropriate advice regarding timing of the procedure?
Options
A
Perform chorionic villus sampling immediately at 9+5 weeks
B
Perform chorionic villus sampling at exactly 10+0 weeks whenever possible
C
Wait until 15+0 weeks and perform chorionic villus sampling
D
Do not perform chorionic villus sampling before 10+0 weeks and, where possible, perform it from 11+0 weeks
E
Chorionic villus sampling should only be performed after 14+0 weeks
Explanation
RCOG recommends that chorionic villus sampling should not be performed before 10+0 weeks of gestation. Where possible, the procedure should be performed from 11+0 weeks onwards because procedures at earlier gestations may be technically more challenging. CVS performed before 10+0 weeks has also been associated with concerns regarding fetal oromandibular and limb abnormalities. Therefore, at 9+5 weeks the procedure should be deferred. Although 10+0 weeks is the minimum gestation, performing CVS from 11+0 weeks is preferred where circumstances allow.
Option Validity
A) CVS should not be performed before 10+0 weeks.
B) Although 10+0 weeks is the minimum gestation, RCOG advises performing CVS from 11+0 weeks where possible.
C) There is no requirement to delay CVS until 15+0 weeks; this gestational threshold applies to amniocentesis.
E) CVS is normally performed considerably earlier and does not need to be deferred until after 14+0 weeks.
Further Reading
Navaratnam K, Alfirevic Z; Royal College of Obstetricians and Gynaecologists. Amniocentesis and chorionic villus sampling: Green-top Guideline No. 8. BJOG. 2022;129:e1-e15. doi:10.1111/1471-0528.16821.