What are the screening tests for aneuploidy?
Combined first trimester screening test (FTS) is recommended in the first trimester between 11 and 13wks and 6 days period of gestation, when the CRL measures between 45 and 84mm.
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Ultrasound examination of the baby is performed at pregnancy scanning centers in Vijayawada prior to screening test to rule out major structural abnormalities and make a note of nuchal translucency measurement. Mother’s blood is withdrawn to analyse 2 biochemical markers (PAPP-A and b Hcg). Risk for aneuploidy is calculated by a software using maternal age, CRL, NT and biochemical marker values.
Cut off level used to divide high and low risk pregnancies is 1in 250. This test has a detection rate of 90% at a false positive rate of 5% for Trisomy 21.
High risk report of screening test does not mean that the baby is affected, it only implies that the chance of baby having aneuploidy is high and further test is required to confirm the presence or absence of Down syndrome. Confirmatory test is either chorionic villous sampling or amniocentesis.
No further test is recommended for women with low risk for aneuploidy. TIFFA scan at 20 weeks is advised.
Consult Dr. P. Madhavi Latha who is the best obstetrician in Vijayawada
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