The Institute of Obstetricians and Gynaecologists says it's highly unlikely that Down Syndrome will be diagnosed within the proposed 12 week limit for abortions.
The Cabinet is this evening expected to formally approve holding a referendum on the 8th amendment later this year.
It follows an Oireachtas committee recommendation that the amendment is repealed, and abortion without restriction be allowed for up to 12 weeks into the pregnancy.
The issue of disabilities have become one of the most controversial points in the debate about potential reform of Ireland's abortion laws.
In a statement, the Institute of Obstetricians and Gynaecologists has moved to provide 'factual background' to the debate.
They say that women typically first access ante-natal care when they are between 12 and 20 weeks pregnant, with private patients sometimes having access to scans a few weeks earlier.
According to the institute, the initial basic scan and blood tests do not specifically screen for abnormalities, although abnormalities can be observed 'in very rare cases'.
Screening tests, meanwhile, are either requested by the woman or offered to them by their doctor. However, the results of those tests are rarely available within the first three months of a pregnancy.
The institute concludes: "It is clear [...] that diagnosis of chromosomal abnormality, while technically possible, can rarely or realistically be achieved before twelve weeks. To suggest therefore that disability will be eliminated by enacting legislation in line with the recommendations of the Oireachtas committee is misleading."
Chair of the Institute of Obstetricians and Gynaecologists, Dr Peter Boylan, says diagnosing Down Syndrome is a complex process.
Speaking on The Pat Kenny Show, Dr Boylan observed: "It's not straightforward, and it's not realistic to suggest that Down Syndrome can easily be diagnosed at less than 12 weeks.
"That's why people should take comfort from the Oireachtas committee recommendations, that termination will not be allowed for children with disability."
You can read the institute's full explanation of screening for chromosomal abnormalities below:
"Much of the recent debate has focused on Trisomy 21 (Down syndrome), a chromosomal abnormality. There are two ways to screen for Trisomy 21. Firstly, an abdominal or transvaginal ultrasound is performed to measure the thickness of translucent tissue in the fetal neck (nuchal translucency) and to confirm the duration of the pregnancy. This may be performed from 11 to just less than 14 weeks. In parallel a blood test between 10 and 13 weeks measures particular proteins in the mother’s blood. The combined results of the blood test and the scan will give assessment of the degree of risk of a chromosomal abnormality, (for example 1:600 or a 1 in 600 chance). It is important to state that this is not a diagnosis.
"A second method of screening is a blood test to analyse free fetal DNA in the mother’s blood stream. This test (e.g. Harmony, Panorama) can be performed from nine weeks onwards. These tests cost upwards of €500 and are not funded by the State which is an obvious limiting factor for many women. If organised through the public system women still have to pay for it. There is no facility in Ireland to analyse the samples so they have to be sent to the UK or the USA for analysis. Results are generally available within two weeks. These tests are not 100% reliable, and so a further, diagnostic, test must be performed to confirm or refute the diagnosis."