Prenatalsafe® 3 Test

Most of us have a normal complement of chromosomes, this being 46 in total, made up of 23 pairs. In trisomy, there is an additional copy of a particular chromosome, resulting in a total of 47 chromosomes. The most frequently occurring trisomy is trisomy 21, more commonly known as Down syndrome. Other trisomies include trisomy 18 and trisomy 13, known more commonly as Edwards’s and Patau Syndrome, respectively.

• Trisomy 21 is found in around 1 in 700 births and the risk of having a baby affected by trisomy 21 increases with advancing maternal age. The condition is associated with learning disability and some structural problems within the baby’s major organs, most commonly heart abnormalities. The life expectancy is around 60 years.
• Trisomies 18 and 13 are found in around 1 in 7,000 births and the risk of having a baby affected by one of these trisomies also increases with advancing maternal age. These conditions are associated with severe learning disability and multiple physical abnormalities. Most affected babies die before or soon after birth, and rarely survive beyond the first year of life.

• Pregnant women from a gestational age 10 +0 weeks.
• Both singleton and twin pregnancies
• Natural conception or assisted conception e.g. In vitro fertilization (IVF).

The Prenatalsafe® 3 test will not be offered:

• If the expectant mother has not had ultrasound scan (to determine gestational age and pregnancy type – singleton/twins/triplets/etc.,)
• To expectant mothers below 10 weeks gestation
• For pregnancies greater than twins (e.g., Triplets)
• If the mother has Down’s syndrome, or balanced translocation or mosaicism of Down’s syndrome, Edwards’ syndrome or Patau’s syndrome
• If the mother received an organ transplantation
• If the mother received a blood transfusion within a period of < 4months
• If the mother received allogeneic stem cell therapy
• If the mother has been diagnosed with a malignancy
• If the mother has received immunotherapy, excluding intravenous immunoglobulin (IVIg) treatment

During pregnancy, the placenta sheds the baby’s (fetal) DNA into the mother’s blood. A blood sample is taken from the expectant mother. The circulating fetal DNA is isolated from the plasma component of the maternal blood and is then evaluated to determine the chance of having a baby with a chromosomal abnormality (e.g., Trisomy 21, 18 or 13).

It is important to note, that the Prenatalsafe® 3 test is a screening test and is not a diagnostic test. If a high- chance result is obtained, the fetal medicine consultant will call you to discuss your options including diagnostic testing (chorionic villus sampling or amniocentesis).

DETECTED (High Probability/Chance)

Aneuploidy detected: indicates that the test has produced a result consistent with an aneuploidy of one (or more) of the chromosomes investigated. However, this result is not diagnostic and therefore does not guarantee that the fetus has the condition. Your consultant will call you to discuss the results in detail. The recommended follow-up is an invasive prenatal diagnosis test, such as chorionic villus sampling (CVS) or amniocentesis.

NOT-DETECTED (Low Probability/Chance)

Aneuploidy not detected: indicates that the test did not detect any aneuploidies for the chromosomes investigated. One of the major strengths of NIPT is the very high negative predictive value – which means that if you get a low chance result it is very unlikely that your baby will have one of the trisomies screened for. However, this result does not guarantee that the fetus does not carry these abnormalities.

INCONCLUSIVE RESULT (approximately 1%)

In certain cases where the sample did not pass the quality parameter thresholds, an inconclusive result is issued. In such cases, the expectant mother will likely be asked for a new blood sample in order to repeat the test. The re-test might still produce an “Inconclusive result” (in about half the cases) and a discussion with our specialist consultants is needed to determine the next steps.

Prenatalsafe® 3 has sensitivity and specificity higher than 99.9% with a very low incidence of false positives and false negatives, below the 0.1% of cases. For more information you can check the journal studies below:

Sensitivity, specificity, and limitations: Pertile et al., 2021. Concordance of the test for trisomy 13, trisomy 18 and trisomy 21 is 99.9% for singleton pregnancies (Pertile et al., 2021). For fetal sex, concordance was 100% for both ‘female’ and ‘male’ (based on newborn physical exam) and for XX and XY (based on cytogenetic results). Pertile et al. 2021 – DOI: 10.1093/clinchem/hvab067

The test is performed in the UK and it therefore we will call you with your results within 5 working days. We will also email a copy of the report after we have called you.

If you wish to have more extensive NIPT testing, you should consider Prenatalsafe® Complete Plus and you can find more information on this test by clicking here.