Screening tests can give a very accurate amount of information without necessarily being definitive, and may lead to further test being required, such as follow up ultrasound or invasive testing such as amniocentesis or chorionic villus sampling. There's quite a lot of things that a baby can be born with that cannot be detected by blood tests or ultrasound E.G autism, some forms of cerebral palsy, allergic disorders such as asthma, eczema, etc. A common test that should be offered to all women i