Screening tests in the second 3 months of pregnancy
Screening tests in your second trimester (your second three months of pregnancy) are valuable if you were too late for the first trimester screening or if it is not available where you live. The test can be done between weeks 14 to 18 of your pregnancy, but is ideally done between 15 to 17 weeks. This test is also called the maternal serum screen (MSS) or the triple test.
How is the test done?
A sample of your blood is taken at a pathology collection centre and tested for 3 hormones (estriol, free B-hCG and alpha fetoprotein). The levels of these hormones provide information on your risk of having a baby with Down syndrome or a neural tube defect like spina bifida.
Results should be available within a week and will be given to you by your doctor.
Understanding the results
The results are given as the risk or chance your baby will be affected:
- ‘Not at increased risk’ means the chance of your baby having Down syndrome or a neural tube defect is very low (less than 1 in 300, or 0.0033 per cent). A different birth defect could still be present but this risk is also low.
- ‘At increased risk’ means the risk of your baby having:
- Down syndrome or another chromosome abnormality is greater than 1 in 300 (between 1 in 10 and 1 in 300)
- a neural tube defect lies between 1 in 12 and 1 in 128.
If you are at increased risk additional diagnostic tests will be offered to confirm whether or not your baby has Down syndrome (using chorionic villus sampling or amniocentesis tests) or spina bifida (using ultrasound).
Limitations of the test
One in every 20 women tested will be told they are at increased risk. This does not mean there is definitely something wrong but you might want to consider having further diagnostic tests.
There may be costs for these screening tests. You may be able to claim part of this cost from Medicare (external site). Please ask when you book your appointment about the costs and any rebates available for the screening tests.
- Screening tests are routinely done in the first trimester (first 3 months of pregnancy) or second trimester (second 3 months of pregnancy).
- If your screening test results shows your baby is at increased risk you may wish to have diagnostic tests. Diagnostic tests confirm the presence of a condition and are very accurate.
- Some diagnostic tests can increase the risk of pregnancy loss (miscarriage).
- Screening and diagnostic tests during pregnancy cannot detect all health conditions.
Office of Population Health Genomics
This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.