screening of congenital diseases

[docrupali]

hello everyone.i am Dr.Rupali.
can someone plz let me know which screening tests like amniocentesis & chorionic villus sampling are preffered & when in screening conditions such as downs & haemoglobinopathies?

Both can be used

Amniocentesis :

* 16 weeks of gestation
* foetal loss rate : 0.5-1%
* cell culture takes 3 weeks ( abnormal pregnancy terminated in late stage )
* can also be used to measure protein levels in the amniotic fluid - for example, AFP and acetyl- cholinesterase in suspected cases of neural tube defects
* 17-alpha-hydroxyprogesterone levels can be measured in suspected cases of adrenogenital syndrome

Chorionic villus sampling :

* 10 weeks of gestation
* karyotyping takes 2 days
* gene probe analysis takes 3 weeks ( termination can be earlier and safer ).
* fetal loss : 4%
* may cause fetal malformation
* it does not detect neural tube defects

[dr-mex]

Down screening
The triple test assesses the risk of having a Down's baby based on:

maternal age
maternal serum markers - alpha feta protein, unconjugated oestriol and total human chorionic gonadotrophin.
Serum is taken from 15-20 weeks gestation, ideally 16 weeks. A high hCG, low AFP and low oestriol suggest a Down's child. Results are expressed in terms of the risk of having a Down's child eg. 1 / 145. Detection rates range from 45-65% with a 5% false positive rate. Those with a risk greater than 1 in 200 are offered amniocentesis.

Other risks may also be detected eg. a high AFP suggests a neural tube defect.

Patients need to be counselled:

it is not universally available on the NHS
the value of the test needs explanation