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Frequently asked questions

Down syndrome is a lifelong condition that causes varying degrees of delay in learning and development. It is a genetic condition that usually happens by chance, but may be inherited in some instances.

Babies with Down syndrome may have many or only some of the features associated with the condition. They tend to have reduced muscle tone and may have heart, bowel or other medical issues.

While most people have 23 pairs of chromosomes in each cell of their body, people with Down syndrome have an extra copy of chromosome 21. This is why Down syndrome is sometimes called trisomy 21.

Down syndrome is the most common condition indicated by screening. Other conditions that may be indicated include trisomy 13, trisomy 18, neural tube defects or some rare metabolic or genetic disorders. These may be more or less severe than Down syndrome.

Other sources of information include:

Frequently Asked Questions 

Should I have screening for Down syndrome and other conditions?

Only you can make the decision about whether to have screening or not. Some women want to know about possible conditions and some do not. Your maternity care provider or GP can provide you with resources and details of relevant organisations for additional information to help inform your decision. Women who choose not to be screened will be supported in their decision.

What is the difference between screening and diagnostic testing?

Screening provides an indication of the chance of a baby having the condition screened for. Screening does not give a definite diagnosis and does not identify all babies who have the condition, but it gives an indication of risk. A low risk result means there is very little chance that the baby has the condition screened for. An increased risk result means there is a higher chance that the baby has the condition. 

Diagnostic testing is offered to women with an increased risk result. Only diagnostic testing can determine if a baby actually has the condition.

When should I have the test?

First Trimester Combined Screening combines a blood test result and a nuchal translucency scan result. The blood test is taken between 9 weeks and 13 weeks 6 days of pregnancy. The nuchal translucency scan is an ultrasound scan which is done between 11 weeks and 13 weeks 6 days of pregnancy. Both the blood test and the nuchal translucency scan need to be completed to obtain a result for this screening.

Second Trimester Maternal Serum Screening is a single blood test best taken between 14 and 18 weeks of pregnancy, but can be taken up to 20 weeks.

How does it work?

Antenatal screening for Down syndrome and other conditions measures levels of specific hormones and proteins in your blood. Combined with your age, weight, due date, and other information, the tests calculate how likely you are to be carrying a baby with Down syndrome or another condition screened for. The test will return either a low or an increased chance result.

Who will give me my result?

Your maternity care provider, or the person who referred you for screening (this might be your doctor), will give you your result. They will tell you whether the result is low chance or increased chance.

What do my results mean?

Your maternity care provider will have the results of your screening in about a week to 10 days. They will be able to tell you whether you have a low or increased chance of having a baby with Down syndrome or another condition. They will discuss what this might mean for you.

  • a low risk result means there is very little chance that your baby has any of the conditions screened for. It does not entirely rule out the possibility.

  • an increased risk result means there is a higher chance that your baby has Down syndrome or another condition. This does not mean your baby has the condition.

What is offered to me if my result is increased chance?

If your result is increased chance, diagnostic testing and referral to a specialist obstetrician for more information are available to you. Your maternity care provider will discuss your options and offer to refer you to a specialist. The specialist will give you more information to help you decide whether or not to have diagnostic testing.

Only diagnostic testing can confirm whether or not your baby has a condition before he or she is born. Diagnostic testing looks at the chromosomes from the baby’s cells to find out whether the baby has Down syndrome or another condition.

The diagnostic tests that may be offered are:

  • before 14 weeks: chorionic villus sampling – a sample of the developing placenta (whenua) is taken and sent to the laboratory for analysis
  • from 14 weeks: amniocentesis – a sample of amniotic fluid (waters around the baby) is taken and sent to the laboratory for analysis.

Amniocentesis and CVS have some risks, including a 1-2% chance of miscarriage. Your specialist will talk to you about the risks.