Detection of autosomal trisomies in second trimester of pregnancy

Trisomy is a type of polysomy.
In which instead of normal two instances, three instances of particular chromosome can be seen.
 The trisomies that can commonly affect the intrauterine fetus are
trisomy 21 ( Down syndrome), trisomy 18 (Edwards syndrome),
 trisomy 13 Patau syndrome.
The chances of having babies with trisomies increases with maternal age.
The possible risk of these trisomies can be detected during pregnancy by screening tests.
In second trimester:
-Quadruple test:
It is a blood test.
It should be done between 16 to 22 weeks.
In which levels of
AFP (Alfa feto protein)
hCG (Human chorionic gonadotropin)
uE3 (unconjugated estradiol)
Inhibin A are analyzed.

High HCG, inhibin A levels, low AFP and uE3 levels indicate high risk for trisomies especially Down syndrome.
Triple test measures first three and Inhibin A is not included in it.

Amniocentesis:
It is a invasive test and can be used as a diagnostic test.
Can be performed between 16 to 21 weeks.
By this amniotic fluid is collected and possible fetal cells in it are analyzed for chromosomal abnormalities.
It is having little bit higher risk for miscarriage and infections.

TIFFA scan (Targeted imaging for fetal anomalies):
It is a ultrasound examination to detect fetal anomalies.

It should be performed between 18 to 22 weeks.

By combined result of all these investigations one conclusion can be drawn regarding the possibility of trisomies.


Detection of autosomal trisomies in first trimester:
detection-of-autosomal-trisomies-in first trimester