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Results of Antenatal screening
Most screening tests are carried out in early pregnancy. It’s very important to remember that a screening test is not diagnostic. The results of a screening test are either ‘screen positive’ or ‘screen negative’. A screen positive result means that the risk of the baby developing an abnormality is high enough to consider having prenatal diagnosis. It doesn’t mean that the baby is definitely affected, and most women with screen positive will have healthy babies. A screen negative result means that there isn’t a high risk of abnormality. However, it doesn’t mean that all possible problems can be ruled out.
The reliability of the results is based on the 'detection rate' compared with the 'false-positive rate'. The detection rate is the percentage of affected pregnancies that are rightly identified as high risk, and the false-positive rate is the percentage of unaffected pregnancies that are wrongly identified as high risk.
Even if the screening result is positive, you will not necessarily be offered a prenatal diagnosis. This because the tests are invasive and some carry a slight risk of miscarriage. Instead, doctors may recommend certain women have further tests based on other risk factors, including their age, medical history and family history.
You do not have to have to have prenatal diagnosis if you don’t want to. For many parents-to-be it is a very difficult decision, and it’s important to think about what the results would mean if they were positive.
