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Pregnancy Screening Tests

22nd Sep 2016

The Harmony Pre-natal test has exceptional accuracy and is growing in popularity as a primary screen in pregnant women of any age or risk category.


A maternal blood sample can be analysed as early as 10 weeks gestation and at any time throughout pregnancy. The test analyses small fragments of DNA from the fetus and placenta present in the maternal circulation. It tests for Trisomies 21,18 and 13, and studies have shown that it shows detection rates for Trisomy 21 (Down Syndrome) greater than 99%.


The Harmony test is also able to reduce false-positives results. This means that referral to an amniocentesis can be avoided, but it is important to remember that it is not a diagnostic test, but rather a very accurate screening test. A mother with a high-risk result should be told that the pregnancy may be affected and diagnostic testing is required for diagnosis.


During your pregnancy, you will also be offered a blood test to see if you have three infectious diseases, Hepatitis B, human immunodeficiency virus (HIV), or syphilis. This are offered at your booking appointment with a midwife when you are around 8-12 weeks pregnant.


All pregnant women in England are offered a blood test to find out if they carry a gene for thalassaemia and sickle cell disease. These are inherited blood disorders. If you are a carrier of sickle cell or thalassaemia you can pass these conditions on to your baby.


If the mother is found to be a carrier, screening is also offered to the father. This test should be offered before you are 10 weeks pregnant. It is important that the test is done early as if you find out you are a carrier, you and your partner will have the option of further tests to know if your baby will be affected.


The 20 week scan is also a screening test as it checks for major physical abnormalities in your baby, although it can not pick up every problem. The scan looks in detail at your baby’s bones, heart, brain, spinal cord, face, kidneys and abdomen. It allows the sonographer to look specifically for 11 conditions, some of which are vary rare.


It is important to remember that scans can not find all problems, and there is always a chance that a baby may be born with a health problem that scans could not have seen. Having a test to make sure you and your unborn baby is healthy sounds like a sensible idea. If everything is fine, you will feel reassured, but remember that even the best screening tests may not be 100% accurate.





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