A 32-year-old woman is 9 weeks pregnant and has a 10 year old Down's syndrome child. What test would you recommend for the mother so that she can know about her chances of getting a Down's syndrome baby is this present pregnancy. How will you assure the mother about the chances of Down's syndrome in the present pregnancy?
(A) Blood test (B) USG (C) Chorionic villus sampling (D) Assure her there is no chance since she is less than 35 years of age
(C) Friends – In Patients with previous H/O Down’s syndrome the only confirmatory test, which tells us with 100% reliability of the chances of Down’s syndrome in present pregnancy is “Karyotyping”.
The sample for karyotyping can be obtained in first-trimester by – chorionic villi sampling and in 2nd trimester by amniocentesis.
So obviously we will think of marking option ‘c’ i.e. chorionic villi sampling as the correct answer but, The Question specifically mentions that patient is 9 weeks pregnant and we all know that if CVS is done before 10 weeks– it can lead to limb reduction defects and oromandibular defects in the fetus \Some people argue CVS is not the correct thing to do at this stage.
Read for yourself what Williams has to say on this issue.
“Early reports of an association between CVS and limb. Reduction defects and oromandibular limb hypogenesis caused a great deal of concern (Burton, 1992; Firth, 1991, 1994; Hsieh, 1995, and all their colleagues). Subsequently, it was shown that limb-reduction defects were associated with CVS performed earlier in gestation—typically around 7 weeks”
Williams Obs 23/e, p 300