Doctors are to be issued with new guidelines today to help prevent serious risks to babies experiencing slow growth in the womb.
It follows Irish research at seven hospitals on 1,100 babies experiencing growth restriction in the womb.
Distinguishing between small but normally-developing babies and small at-risk babies in the womb has been a major problem in maternity care.
Standard practice has been to consider babies at the bottom of 10% by weight at highest risk.
But the Irish team found that the highest risk is for babies in the bottom 3% by weight, who have an abnormal reading on a particular ultrasound.
A consultant obstetrician has said new guidelines are a hugely efficient development for Irish obstetrics.
Speaking on RTÉ's Morning Ireland, Professor Fergal Malone, Consultant Obstetrician and Gynaecologist at the Rotunda, and Chair of Perinatal Ireland, said the research would also change the practice of obstetrics internationally.
Prof Malone said the research, which redefines what a small baby is in the womb, would allow for focus on where the limited resources in obstetric ultrasounds should be placed.
He said the new practice would be much more efficient and would allow for reassurance for patients having what he described as a "normally small baby".
Prof Malone said Ireland was punching above its weight with this research.
The new guidelines are being issued today to obstetricians, trainees and midwives.
Doctors say they will also be useful to women and their partners.
The research was conducted by Perinatal Ireland, a multi-centre all-Ireland consortium and the initiative was coordinated by the Royal College of Surgeons in Ireland.
It was funded by the Health Research Board.