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What is Chorionic villous sampling is needed in all except and explain in detail?
Chorionic villous sampling(CVS) is done at the 10 - 13 week of gestation to diagnose conditions which could be debilitating or life threatening for the unborn fetus. Neural tube defects are best assessed at a later gestation around 20 weeks though the earliest to be picked up is ANENCEPHALY which can be picked up by 10-12 weeks with USG. The most specific indicator for Neural tube defects is the acetylcholinesterase