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How we monitor the health of your baby

CollapseScreening and diagnostic tests

Screening tests are used to assess the chance of your baby having a chromosomal or structural condition. If a screening test suggests an increased chance of a particular condition, a diagnostic test is performed to find out if the condition is actually present. Around 2% of all babies are born with some kind of abnormality. Most are minor, such as fused toes or skin tags. However, a very few babies will have more major problems, such as heart defects, spina bifida and chromosomal irregularities. In most cases, screening tests provide reassurance that everything is OK. The National Screening Unit oversees pregnancy and newborn screening in New Zealand

ExpandMaternal serum screening and nuchal translucency ultrasound scan

This is a blood test performed between 9 and 14 weeks of pregnancy, combined with a special scan performed between 11 and 14 weeks. The results of these two screening tests are combined to calculate the risk of the baby being affected by Down syndrome and other rarer related syndromes.

The blood test measures the amounts of certain substances in the mothers blood (serum), which are found in differing levels in pregnancies where the baby has Down syndrome. The scan looks specifically for increased swelling at the back of the baby's neck - a characteristic of babies with Down syndrome.

The final result divides women into two groups - those who are at higher risk of having a baby with Down syndrome, and those with a lower risk. Women in the higher risk category are offered a diagnostic test to confirm or exclude Down syndrome and other related syndromes.

This combined testing as known as MSS1 (maternal serum screening 1st trimester).

Some women may have missed the cut-off time of 14 weeks to undertake the MSS1 testing. In this case, a different bood test can be performed between 14 and 20 weeks of pregnancy to calculate the risks in the same manner as the MSS1 testing. This test is known as MSS2 (maternal serum screening 2nd trimester).

ExpandCell free DNA screening test

Origins is the first obstetric practice in New Zealand to offer this latest test to our patients. It is a more sensitive test for chromosomal abnormality than the MSS1 test described above. A sample of the mother’s blood is taken and sent to a laboratory in California, where it is analysed for genetic abnormalities which may be present in the baby. Cell free DNA testing incurs an extra charge as it is not funded by the New Zealand government. Please discuss this with your Origins obstetrician if you’d like to know more.

ExpandDiagnostic test: chorionic villus sampling

Women may wish or be advised to undergo chorionic villus sampling (CVS), a test performed between 11 and 13 weeks that can detect more than 200 genetic disorders. It involves removing a small piece of tissue from the developing placenta. The advantage of CVS is that it can be performed early in pregnancy. However, there is a small associated risk of miscarriage of about 1%.

ExpandDiagnostic test: amniocentesis

If your screening tests results show an increased risk of chromosomal problems in the baby, we will discuss and offer amniocentesis. Amniocentesis is usually performed at or beyond 14 weeks. It involves removing a small samplearound 18mL of the amniotic fluid that surrounds the baby. Cells from the baby found in the fluid are cultured to grow the baby's chromosomes. Amniocentesis has a miscarriage rate of less than 1%. A disadvantage of amniocentesis is that it can't be performed as early as CVS.

ExpandAnatomy ultrasound scan

We recommend all our patients have an anatomy ultrasound scan. This is performed between 18 and 20 weeks, when the baby is big enough to allow accurate identification of all major organs. During this scan you are usually able to find out the sex of the baby, but only if you want to know! This scan is able to detect nearly all major birth defects if they are present, and is important in assessing the development of the placenta too.

ExpandFetal Growth Scans

During the final three months of pregnancy, your baby is fully formed but still needs to grow well to be healthy. Your Origins obstetrician may suggest detailed scans to carefully monitor your baby’s growth, in addition to the scans that he does at each consultation. If your pregnancy is complicated by conditions such as high blood pressure or diabetes, these scans are especially important.

ExpandDay Assessment Unit

Should your pregnancy become particularly complicated, you may require medical checks up to three times per week. In these cases, we may make use of the Day Assessment Unit at National Women’s Hospital, to keep you and your baby under close and frequent observation.