Is there any risk?
No, The testing is non-invasive: it involves taking a blood sample from the mother. The pregnancy is not put at risk of miscarriage, or from other adverse outcomes that are associated with invasive testing procedures such as amniocentesis.
What is the Accuracy?
Clinical studies have shown that the Non-Invasive Prenatal Testing procedure has exceptional accuracy for assessing fetal trisomy risk. A ‘high risk’ result is indicative of a high risk for a trisomy. The test identifies in singleton pregnancies more than 99% of fetuses with trisomy 21, 98% of fetuses with trisomy 18, and 80% of fetuses with trisomy 13, and 96% of fetuses with Turner Syndrome.
X and Y analysis provides >99% accuracy for fetal sex. Accuracy for detecting other sex chromosome anomalies varies by condition. After the test, the number of women required to have a CVS or an amniocentesis is less than 1%. It is important to note that if the test results show there is a high risk that the fetus has trisomy 21, 18, 13 or sex chromosome conditions, it does not mean that the fetus definitely has one of these conditions, although it is highly likely.
For this reason, in the event of a ‘high risk’ (or positive) result, follow-up testing by an invasive procedure is recommended. In the same way if the test results show that there is a’low risk’ that the fetus has trisomy 21, 18, 13 or sex chromosome conditions, it is unlikely that the fetus has one of these conditions. However, there is a very small risk that not all trisomy fetuses will be detected.
All results should be interpreted by a clinician in the context of clinical and familial data. Patients should continue with their usual scan appointments following testing.
Who can have the test done?
The Non-Invasive Prenatal Testing procedure can be performed for any woman with a pregnancy of at least 9 weeks’ gestational age. It can also be ordered for all IVF singleton pregnancies, including those with egg donors. Samples from pregnant women with twins naturally conceived, or those conceived using the patient’s own egg, are also accepted. This test does not assess risk for mosaicism, partial trisomies or translocations.
The results will be ready in approximately one to two weeks, at which time most women can have their 12-week scan for a detailed examination of the fetal anatomy, including measurement of nuchal translucency, nasal bone and other important factors. In this visit, patients can discuss the DNA and ultrasound results with their obstetricians.
On the basis of the NIPT result and the ultrasound findings, a patient can decide whether or not she wants to have an invasive procedure (for example, CVS or amniocentesis).
Will I need to repeat the test?
There needs to be enough fetal DNA in the maternal blood to be able to provide a result. If there is insufficient fetal DNA in the sample (occurring in 3% of cases), another blood sample from the mother may be required. This will be processed in the laboratory at no extra charge.
What is the process?
Once the mother has taken an independent personal decision that she wants to have the non-invasive prenatal test performed, she will be asked to sign a consent form and her blood sample can be taken from a vein in her arm.
Who carries out the analysis of the test?
The sample and completed request form will be sent to the relevant laboratory, where the fetal DNA will be extracted from the blood sample, and a result will be provided.
Will the mother need to have any other tests?
Non-Invasive Prenatal Testing does not provide information on other rare chromosomal abnormalities. If the ultrasound scan shows a high nuchal translucency or other major physical defects such as brain abnormalities, heart abnormalities, the risk for some rare chromosomal defects may be high. In such cases, the mother may choose to have a CVS or an amniocentesis.
The Non-invasive prenatal test does not provide information on other physical defects such as spina bifida, or information on fetal growth. It is therefore advisable that the mother has all the usual ultrasound scans during her pregnancy
Transfer of the mother’s information outside the European Union
For the purposes of carrying out NIPT, the mother’s personal information may be transferred outside of the European Union, for example to the USA. Please be aware that the laws applicable to her personal data in the USA are different from those operating in the UK and Ireland.