EMQ — Extended Matching Question · Review
Question 29
Feto-maternal medicine → Perinatology
Classification
Question
EEMQAnswer Bank
Correct Answer
Explanation
Chorionic villus sampling provides placental villi for definitive prenatal diagnosis and is usually performed between 11+0 and 13+6 weeks. RCOG advises that CVS should not be performed before 10+0 weeks and, where possible, should be performed from 11+0 weeks. Amniocentesis should not be performed before 15+0 weeks because earlier amniocentesis is associated with increased pregnancy loss and fetal talipes. Therefore, for a woman seeking definitive invasive diagnosis at 11+3 weeks, CVS is the most appropriate procedure. CVS at 9+5 weeks is too early, while performing it at 10+2 weeks is above the absolute minimum but earlier than the gestation recommended where possible. Amniocentesis at 13+6 or 14+4 weeks would also be too early. Waiting until 20 weeks is unnecessary when an appropriate diagnostic procedure is already available.
Option Validity
A) CVS should not be performed before 10+0 weeks.
B) Although CVS may be performed from 10+0 weeks, RCOG recommends performing it from 11+0 weeks where possible.
D) Amniocentesis should not be performed before 15+0 weeks.
E) Amniocentesis at 14+4 weeks remains earlier than the recommended minimum gestation of 15+0 weeks.
F) Amniocentesis at 15+2 weeks is an appropriate diagnostic procedure at that gestation, but CVS at 11+3 weeks permits appropriate definitive diagnosis earlier in this scenario.
G) There is no need to defer invasive diagnosis until 20 weeks when CVS can appropriately be performed from 11+0 weeks.
H) An invasive diagnostic procedure is appropriate; CVS at 11+3 weeks meets the recommended timing.
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.