| Understanding pregnancy tests
The most common tests offered are:
Before you can make any decisions about which antenatal tests to have (or whether to have any at all), the first thing to understand is the difference between a screening test and a diagnostic test. Screening test - tells you what your risk is of having a baby with a particular health problem. Diagnostic test - tells you whether your baby has or has not got a particular health problem. Screening testsA screening test estimates your risk of having a baby with a serious health problem such as Down’s syndrome or spina bifida or some rarer condition such as Edward’s syndrome. It can’t tell you for certain whether your baby has or has not got one of these conditions. So, for example, you might have a blood test when you are 16 weeks pregnant and be told that your risk of Down’s syndrome is 1 in 140. This means that there is only one chance in 140 that your baby will have Down’s syndrome. Or, to look at it another way, you are far more likely to have a normal, healthy baby than a baby with a severe disability.
Screen negativeThe result of your screening test may simply be described as screen negative. This means that your risk of having a baby with a problem is less than 1 in 250. Your risk is so small that it’s not even quantified. Nonetheless, a screen negative result does not mean that you definitely have a healthy baby. Screen positiveIf your test result is screen positive (ie, greater than 1 in 250) you will be quoted a figure such as 1 in 100 or 1 in 40. Only you can decide whether you are prepared to accept that risk or whether you want to have a diagnostic test to get more information - there’s more about making these difficult decisions later on. Diagnostic testsA diagnostic test can tell you for certain whether your baby has Down’s syndrome or spina bifida or some other major health problem. The result is conclusive: it’s a yes/no situation.
Where to next?
|
