The difference between screening and diagnostic testing: 

• Screening gives you an increased or low risk result of any complications but does not give a definitive diagnosis 
• Diagnostic tests confirm if the condition being tested for is present 

At your first antenatal visit you will be offered information regarding these tests. For well women with no pre existing medical conditions and well babies the expected tests during pregnancy include: 

• Blood tests At booking, 28 weeks and 36 weeks, and as clinically indicated at any stage. 
• Ultrasound scans NT scan for chromosomal abnormalities at 11-13 weeks + 6 days, Anatomy scan at 18-20 weeks and as clinically indicated at any stage.

Women with pre-existing medical conditions, or who develop pregnancy related conditions, or who are exposed to some illnesses or toxins or who are pregnant with twins/triplets may require additional blood tests or scans. You must be informed with regards to all testing during pregnancy and give consent for these tests. You may choose not to have some tests/screening but remember that these assist your LMC to provide appropriate care for you and your baby. They help ensure you have appropriate information from which to make informed choices regarding the health of you and your baby. 

First AN bloods include: 

• Blood group and rhesus factor (negative or positive blood group) 
• Screening for antibodies 
• Full blood count including Haemoglobin count (a test for anaemia) and Platelet count (clotting factor) 
• Tests for Syphilis, immunity to Rubella, immunity or carrier status of Hepatitis B, HIV (this is a screening for HIV and may be followed by diagnostic HIV blood tests) and may include screening for Hepatitis C 
• HbA 1c test is a screening test for glucose levels 

First trimester combined screening 

Between 9 and 13 weeks + 6 days, you may choose to have combined screening for chromosomal abnormalities, including Down syndrome. This is a combined scan and blood test which gives a more accurate screening result than a scan on its own. It includes information such as age, weight, ethnicity, gestation, previous pregnancies with chromosomal abnormalities and if this pregnancy involves assisted reproduction. 

• Blood test MSS1 blood test between 9 and 13 weeks + 6 days measures the pregnancy associated plasma protein-A (PAPP-A) and beta human chorionic gonadotrophin (BhCG). 
• Ultrasound scan between 11 and 13 weeks, 6 days measures the thickness of the fluid filled space at the base of baby’s neck (nuchal translucency - NT). Your screening results will be low or increased risk. Your LMC will discuss these with you and offer further tests if the result suggests an increased chance. 

For more information about screening see www.nsu.govt.nz. 

Second trimester maternal serum screening (MSS2) 

If you did not have the NT scan or MSS1 bloods and are past 14 weeks in your pregnancy you may have this screening blood test instead. It tests four different substances in your blood and includes additional information as in MSS1 bloods. More about this on page 62. 

Additional tests during pregnancy may include: 

Blood tests for 

• Gestational Diabetes- HbA1C, Polycose or Glucose Tolerance Test at any stage (especially if you have a family history of diabetes, certain ethnicities and women with higher BMI’s) but most frequently GTT at 28 weeks 
• Ferritin- a test for anemia which tests your body’s stored iron levels. These may drop as baby grows and may mean you need to increase your iron consumption through diet or supplementation 
• B12 
• TORCH screen-testing for exposure to some infections such as Toxoplasmosis, Rubella, Cytomegalovirus, Herpes or other infections 
• Extra blood tests for other reasons 

Diagnostic tests such as 

• Chorionic Villus Sampling (CVS)
• Amniocentesis  

(More info below)

Ultrasound scans for 

• Growth of baby 
• Placental position 
• Amniotic fluid levels 
• Extra scans for other reasons 

Non-invasive prenatal screening (NIPS) 

NIPS is a blood test that screens pregnancies chromosomal abnormalities including Down syndrome, Edwards syndrome and Patau syndrome. NIPS has the highest accuracy for Down syndrome among the prenatal screening tests and can be performed anytime from 10 weeks pregnancy onwards.

Gestational Diabetes testing 

A test for gestational diabetes mellitus (GDM) is often offered at this time. The Polycose test is a 1 hour, non fasting (must have eaten within 3 hours) screening test and if the result is high you may be asked to have a Glucose Tolerance Test (GTT). The GTT takes 2 hours and you will be required to fast. Some women may have the GTT instead of the Polycose, especially if you have risk factors for GDM. Your LMC will discuss this with you.