What is Prenatal Diagnosis?




Lorene A Temming, George A Macones  

Patients and providers are faced with a wide array of choices to screen for structural abnormalities, aneuploidy, and genetic diseases in the prenatal period. It is important to consider the features of the diseases being screened for, the characteristics of the screening tests used, and the population being screened when evaluating prenatal screening techniques. 

 This link provides the latest information on prenatal screening – www.prenatalscreening.org.au


What is Prenatal screening? 

Prenatal screening, which includes blood tests and ultrasounds may show that a baby has a chance of being born with a congenital anomaly.  

Congenital refers to something that is there before or at birth, and anomaly means ‘a difference’. An unborn baby may be diagnosed with a congenital anomaly when there is something unexpected about their development, health or genetics. 

Prenatal screening is available to all pregnant women. These tests estimate the chance that your baby has a chromosomal or physical condition. Most babies are born healthy. 

 There are different types of tests available. They vary in how exact they are and what information they can give you. No single test checks for all conditions. 

 It is your choice whether you have prenatal screening. Your healthcare provider will be able to give you more information to help you decide.  

What prenatal screening tests are available? 

Screening tests are used to identify the chance of a baby having a chromosomal condition such as Down syndrome. They do not provide a definitive diagnosis. Where a high chance result is returned on a screening test, a diagnostic test should be offered. 

Combined first trimester screening  

Combined first trimester screening (CFTS) adds the results from different tests. Together these results make an estimate about the likelihood of the baby having: 

  • Down syndrome (trisomy 21) 
  • Edwards syndrome (trisomy 18) 
  • Patau syndrome (trisomy 13) 

These tests are: 

  • maternal blood test which looks at different proteins in your blood. 
  • a nuchal translucency (NT) screening ultrasound measures the thickness of the fluid behind the baby’s neck 
  • presence or absence of your baby’s nasal bone – this test happens between 9-13 weeks of pregnancy.  
  • your age and weight 
  • pregnancy age 


Second trimester maternal serum screening 

Second trimester maternal serum screening calculates the risk that your baby has: 

  • Down syndrome 
  • Edwards syndrome 
  • neural tube defects (for example spina bifida)

The test involves: 

  • a blood test 
  • your age and weight 
  • pregnancy age

This test happens between 15 and 17 weeks of pregnancy. It can happen up to 20 weeks. 

Non-invasive prenatal test 

NIPT stands for non-invasive prenatal testing. It involves a blood test taken from a pregnant woman, at least 10 weeks into the pregnancy. It looks at fragments of cells (DNA) found in placental blood. The woman’s blood contains a mixture of her own cell fragments and those from the placenta. Therefore, NIPT screens for fragments of placental cells, NOT the baby’s cells/DNA 


These links provides more information on the NIPT tests 



What is Diagnostic Testing? 


Where screening results indicate a higher chance of Down syndrome or another chromosomal difference, pregnant woman should be offered diagnostic testing. 


Where a pregnant woman chooses to have a diagnostic test, the choice of test should be based on gestational age, the preference of the person and the suitability of the test for individuals. Health care providers should not presume that confirmation of a diagnosis would lead to a decision to terminate the pregnancy. 


There are options when undertaking further testing with diagnostic tests. This is YOUR choice whether or not to undertake diagnostic testing. A specialist referral is recommended to provide you with the information required about what is most appropriate in the clinical circumstances. 


What diagnostic tests are available? 

Chorionic villus sampling (CVS) 

CVS is done between weeks 11 and 14. It can tell you if your baby has Down's syndrome or other conditions such as sickle cell anaemia and thalassaemia. 

The doctor will take a sample from the placenta using a thin needle that is inserted through your tummy. This is done under local anaesthetic and using ultrasound as a guide to make sure the needle is in the right place. Occasionally CVS is done by passing a fine set of forceps through your cervix instead. 

More information on CVS can be found here: https://ranzcog.edu.au/wp-content/uploads/2022/06/Chorionic-villus-sampling-CVS.pdf


Amniocentesis is done after 15 weeks and will diagnose Down's syndrome and other conditions in your baby. 

In this test, the doctor will take a sample of the amniotic fluid that surrounds your baby. As with CVS, this is done with a thin needle inserted into your tummy and the doctor will use ultrasound as a guide. 

More information can be found here: 




 If you have received unexpected news about the development of your baby, firstly, know that you are not alone. One in twenty-two women and their partners will find out that their baby has a major congenital anomaly. 

For many parents, prenatal screening can feel like just a routine appointment. Ultrasounds are often viewed as a chance to see and bond with their growing baby. This means that parents are often unprepared and feel shocked when given unexpected news. 

After the initial shock, expectant parents commonly describe experiencing a roller coaster of emotions and thoughts. Other experiences can include: 

  • Profound sadness and lots of crying 
  • Guilt and worry whether they caused the anomaly 
  • Difficulties or changes in their sleep 
  • A want to avoid people 
  • Anger, frustration, and irritability 
  • Feeling loss of the typical pregnancy and expectations 
  • Feeling unsure of what will come

For some parents, the intensity of emotions eases quickly, and they find a place of hope and acceptance, while others may experience these symptoms for the rest of their pregnancy or into the postnatal period. 

Strategies to help you cope with unexpected news 

There is no single way to cope with unexpected news. Parents are individuals with their own stories, histories, and values. While there are common experiences, how each person moves through their journey is unique, and therefore not all coping strategies will help all parents. 

Parents who have moved through the experience of receiving a prenatal diagnosis often describe these strategies are helpful.  

Finding information 

Most expectant parent find it helpful to learn what they can about their baby’s anomaly. The information helps parents feel like they are more in control and prepared, and this information can be helpful when considering options regarding the pregnancy. Some parents avoid the internet due to concerns whether the information is correct and they prefer to rely on the information offered by their health care team. If you do wish to look for information, it may be helpful to stick to websites of organisations you can trust or ask your care team for guidance to reliable information. 

Talking to loved ones 

Family and friends can be very helpful for some parents who feel they can talk openly and who appreciate the distraction that their loved ones provide. Other parents prefer not to share the unexpected news with their families or friends until they feel ready or until they have more information to answer questions that their families may ask. Talking with a counsellor or other professional may be helpful for all parents and especially important for those who do not feel ready to share the news with family. 

Connecting with others 

Reaching out to other expectant parents who are also going through a complicated pregnancy is often described as helpful. Connecting with condition-specific support groups can provide a way to gain a greater understanding of the lives of people with a particular condition. It may be helpful to remember that due to the nature of support groups, they often attract people at times when support is needed. Therefore, they may also show some of the more challenging sides of life with a condition. 

Planning the next stages 

Being active in the planning and decision making can help women regain some control and autonomy. Planning may include decisions about what tests to undertake or to make plans for the birth or delivery following a termination for medical reasons.  

Turning to religion or spirituality 

Prayer and connection with their religion or spirituality has helped some couples move through the period of prenatal diagnosis. Women report feeling comforted by the thought that God wouldn’t have presented a situation that they couldn’t get through. 

Decision making 

The diagnosis of a congenital anomaly often means that parents are presented with options that they might not have considered earlier, to continue or end their wanted pregnancy. The decision-making time, to continue or end a wanted pregnancy has been described by some women as the hardest stage of the prenatal diagnosis, while for other women, the decision is straightforward. 

The option to end a wanted pregnancy will depend on the anomaly, the stage of pregnancy, and the law. Parents who have made the heartbreaking decision to end their wanted pregnancy often do so to avoid their baby experiencing any suffering, or due to their personal and family needs. 

For parents who continue their pregnancy there are several options available after birth. Many parents will plan to care for their newest family member, while some parents may consider adoption or foster care. Perinatal palliative care teams may be available to support families when birth may also bring limited time with their baby with a life-limiting condition. 

The decision that you make is deeply personal, you will make the right decision for your baby and family. While no one can make this decision for you, non-directive pregnancy support counselling is available to help you explore your options and help you come to your own decision. 

Useful Links 

Through the Unexpected – Prenatal Diagnosis 


Panda - Perinatal Mental Health 


Beyond Blue - Mental Health Support  


 Black Dog Institute - Mental Health Support 


Special thanks for Cope – Centre for Perinatal Excellence for content sharing and providing support for families. 


Confirmation Content

Disclaimer: This publication by Miracle Babies Foundation is intended solely for general education and assistance and it is it is not medical advice or a healthcare recommendation. It should not be used for the purpose of medical diagnosis or treatment for any individual condition. This publication has been developed by our Parent Advisory Team (all who are parents of premature and sick babies) and has been reviewed and approved by a Clinical Advisory Team. This publication is not a substitute for professional medical advice. Miracle Babies Foundation recommends that professional medical advice and services be sought out from a qualified healthcare provider familiar with your personal circumstances. To the extent permitted by law, Miracle Babies Foundation excludes and disclaims any liability of any kind (directly or indirectly arising) to any reader of this publication who acts or does not act in reliance wholly or partly on the content of this general publication. If you would like to provide any feedback on the information please email [email protected].