Non Invasive Prenatal Diagnosis (NIPD)

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Non Invasive Prenatal Diagnosis (NIPD) is developing as a result of several new techniques studying free fetal nucleic acidswhich may allow a diagnosis of certain fetal conditions by taking blood from the mother. Some are used already in the NHS in special circumstances such as:

• determining Rhesus status of the fetus in rhesus disease
• determination of fetal sex in sex-linked conditions

Others will be much more difficult including diagnosing certain genetic and chromosomal conditions in the fetus, one of them being Down's syndrome (Trisomy 21). The advantage of these approaches is the hope that invasive procedures such as an amniocentesis or chorionic villus sampling (CVS) and the associated miscarriage risk could be avoided.

A National Screening statement suggests that "..The preliminary results, although promising, are very much still in development and certainly not at a stage where we would consider using this as a NHS population screening programme. However this will be kept under constant review .." (1)

Notes:

• cell free fetal DNA (cffDNA) can be detected in the mothers blood from 5 weeks of pregnancy and stays in the maternal blood foronly up to an hour after delivery and therefore is not detectable in a subsequent pregnancy
  • there is already a possibility of cffDNA being used for determining fetal sexing and Rhesus status in the UK, but the more complicated use for diagnosing whole chromosomal status such as Down's syndrome is not well established scientifically (1)

Reference:

• 1. NHS Fetal Anomaly Screening Programme (December 2008). Non Invasive Prenatal Diagnosis - the present state of the technology and its use in the NHS.