Several tests are performed throughout the pregnancy to ensure that both you the mother and your baby are doing well.
Early in the pregnancy, screening tests are available to see what the chances are that your baby may have one of the more common genetic problems like Down Syndrome (Trisomy 21).
Whether or not you would like to do genetic screening is an individual decision, and Trent will discuss the options with you at your first visit. Testing can be perfomed as early as 10 weeks pregnant.
'Genetic screening' means assessing what the likelihood is of having a baby with a common genetic problem. A good results provides lots of reassurance and significantly reduces the chances of common genetic problems. An abnormal screening result does not say for certian whether there is a problem but indicates that further testing is required.
There are 2 types of genetic screening tests available.
Firstly, a nuchal translucency ultrasound. This is an ultrasound and a blood test performed at about 12-13 weeks of the pregnancy. It is a combination of a blood test looking at several hormones, and the development of the baby on ultrasound. It gives an estimation of the chances of having a baby with some of the more common genetic problems such as Down Syndrome. It also is a good opportunity to assess the basics of the baby's development. It is mainly targetted at testing for Down Syndrome and similar conditions, but sometimes less common genetic problems can also be suggested at this ultrasound. If there are any abnormalities, then further testing is usually required which might consist of 'non-invasive prenatal screening' or a 'CVS' or 'amniocentesis' (see below). The nuchal translucency ultrasound is the standard, traditional way of doing genetic screening, and is still the recommended option for initial genetic screening for the baby.
Secondly, non-invasive prenatal screening (NIPS) is a blood test that you have from about 10 weeks of the pregnancy. There are several different brands available, common ones are 'Harmony', 'Nest' and 'Generation'. This is a new DNA test where we can detect traces of the baby's DNA in your blood, extract this and work out what the chances are of the baby having some of the common genetic problems. It tests for Down Syndrome and also the next most common genetic problems (trisomy 13, trisomy 18, and sex chromosome problems). It is important to say that it does not test for all genetic abnormalities. The gender of the baby can also be determined with this testing. A normal result with this test is 99.9% reliable for not having a baby with Down Syndrome. An abnormal result usually means there is about an 80 to 90% chance of having a baby with Down Syndrome, and we would always confirm this by doing an amniocentesis or CVS.
NIPS is a bit more accurate than the NT ultrasound at testing for Down Syndrome and a few other genetic conditions, but the NT ultrasound can sometimes suggest other problems that NIPS does not test for. Current advice is to do the NT scan, and use NIPS as an 'optional extra' or to get further information if an abnormality is seen at the NT ultrasound.