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Screening Tests

What is a screening test?

Screening tests look for signs of possible problems with your wellbeing and the way that your baby is developing.

What do they tell us?

Screening tests have limitations; they are unable to detect all conditions. Tests for you are usually to detect the presence of health conditions and diseases that might affect your pregnancy. Tests for your developing baby can determine whether there is an increased chance that the baby has a particular problem. Your LMC can help you to work out what tests are helpful to you and your pregnancy. You will be able to make choices based on the best evidence available.

First antenatal blood screen

This blood test provides a baseline of your iron level, any infections present, your blood type and your rhesus factor (positive or negative).

Polycose/ GTT

This is a routine test recommended for all women between 24-28 weeks gestation. It identifies whether you have become diabetic during pregnancy. If you have gestational diabetes, the results of this test will help to define a treatment plan.

HIV screening

HIV screening is offered as a routine screening test in New Zealand. This infection remains on the increase and greater numbers of women are becoming infected. By routinely offering this screening and identifying HIV positive mothers, there is evidence to show that transmission to the unborn baby is significantly reduced with the use of appropriate medications given to the mother. Being aware of your HIV status has health benefits for both you and your baby.

Ultrasound screening

Ultrasound screening is offered for a variety of reasons. If you can’t remember the date of your last menstrual period, ultrasound can be used to determine when your baby is due. It can also be used to see if you’re expecting twins or more. And at 18-20 weeks, an ultrasound screen can check if your baby is developing normally. There could be other reasons to have an ultrasound scan as your pregnancy progresses, such as monitoring the growth of your baby and the position of the placenta.

Nuchal screening

The foetal nuchal translucency test is a special type of ultrasound scan that will be offered to you between weeks 11 and 14 of your pregnancy. It is used to assess whether your baby might have a chromosomal abnormality, such as Down syndrome. Your LMC will discuss your risk factors with you and provide you with information about the scan. The scan by itself can’t diagnose a chromosomal abnormality, but can indicate whether further investigation is needed. If there are any concerns, a follow-up amniocentesis will be offered to you at 15+ weeks.You can read more about this in our patient leaflets on Antenatal testing and screening for Downs syndrome in pregnancy. 

Combined test

Taken between 10-14 weeks, this is the nuchal translucency screening plus a blood test that measures two specific biochemical markers that are present in your blood. It is the preferred method to assist in early diagnosis of Down syndrome. You can read more about this in our patient leaflets on Antenatal testing and screening for Downs syndrome in pregnancy. 

Your LMC will explain how you will be informed of these results.

Vaginal swabs

Low and high vaginal swabs help to diagnose infections - such as Group B strep, trichomonas, gonorrhoea, syphilis and bacterial vaginosis. Identification and treatment of infections is important for the health of your unborn baby.

Cervical Smear test

It’s important to know that your cervix is healthy. If you are due for a smear test, this will be offered to you at your first antenatal appointment. You can read more about Cervical Smear Tests in our patient leaflets.

Amniocentesis

This procedure has fewer risks when performed between 15 and 20 weeks. A fine needle is inserted through your abdomen into your womb and a sample of amniotic fluid is taken. The chromosomes in amniotic fluid can be used to diagnose chromosomal problems, such as Down syndrome (Trisomy 21), a mental and physical defect. Alpha-fetoprotein in amniotic fluid can also show whether a fetus has problems affecting the spine, lungs or other areas of the body. You can read more about testing through our Amniocetesis and Chorionic Villus Sampling (CVS) patient leaflet.

Chorionic villus sampling (CVS)

Chorionic villus sampling (CVS) is used to detect chromosomal abnormalities such as Down syndrome, as well as various other genetic disorders. Cells are taken from tiny fingerlike projections on the placenta (called chorionic villi) and sent to a lab for genetic analysis. The main advantage of CVS over amniocentesis is that you can have it done earlier - usually around week 10 of your pregnancy. You can read more about testing through our Amniocetesis and Chorionic Villus Sampling (CVS) patient leaflet.

Family violence screening

Pregnancy is a particularly at-risk time for women. Antenatal appointments have been identified as a unique window of opportunity for asking questions relating to family violence and offering support to women.

Urine screening

Urine screening is offered routinely throughout pregnancy. Its aim is to detect proteinuria a marker for pre-eclampsia (a rare complication of pregnancy), urinary tract infections (easily treated with antibiotics) and glycosuria (a marker for diabetes). Your midwife will advise you on the appropriate management.

Sexually transmitted diseases

All women are routinely screened for sexually transmitted infections during their blood tests. If you test positive, your LMC will discuss the results with you and provide the appropriate treatment. There may be reason to involve your partner in the treatment programme to prevent re-infection.
National Women's Health
Phone: 09 307 4949
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