There is significant under-reporting of maternal death rates in the Republic by the Central Statistics Office (CSO), an examination of data from Dublin's three main maternity hospitals has found.
Data from the annual clinical reports of the National Maternity Hospital, the Coombe Women's Hospital and the Rotunda Hospital shows that in five of the 15 years from 1990 to 2004 more maternal deaths occurred in the hospitals than were reported in CSO figures.
For example, in 1995 there were three deaths reported in the hospitals' annual clinical reports but none reported in CSO figures.
In 1999 there were five deaths recorded in the hospitals' annual clinical reports but only one recorded in official CSO figures.
Again in 2003 there were two deaths reported by the hospitals and none recorded by the CSO for that year. In 2004, there were two deaths reported by the hospitals in their annual reports but only one in CSO statistics.
However, there were also years when the CSO figures for maternal deaths in the Dublin area were higher than those reported by the maternity hospitals.
For example, in 2002 the CSO figures put the number of deaths at five while the total reported by the three maternity hospitals was three.
In a letter to the latest edition of the Irish Medical Journal, two doctors - Dr Cliona Murphy, assistant master of the National Maternity Hospital, and Prof Colm O'Herlihy, professor of obstetrics and gynaecology at University College Dublin and the National Maternity Hospital - state that these repeated discrepancies are consistent with "persistently defective case ascertainment by the current mechanisms used by the CSO".
They say "this should be addressed as a matter of priority".
They acknowledge that Ireland has experienced a decline in maternal deaths for more than 60 years but say rates cited by the CSO and taken up by the media suggest that this is one of the safest countries in the world in which to deliver a baby.
"Nevertheless, closer inspection of maternal death rates in the Republic indicate significant under-reporting by the CSO, thus casting considerable doubt on any comparative conclusions, and, in fact, on the overall reliability of figures in recent years," they write.
Joseph Keating, a statistician with the CSO, said yesterday that the CSO collected its figures from death certificates, whereas the hospitals worked from knowing what happened in each case.
If it was obvious from a death certificate that a woman died while pregnant or shortly after childbirth, the CSO would record her passing as a maternal death, but if the death certificate cited the main cause of death as something which anyone could have died of, the death may not be recorded as a maternal death, he said.
"We would like to work more closely with the hospitals to get the figures more correct," Mr Keating said.
He added that it was difficult to collect maternal mortality figures because there were so few of them. Other countries had similar difficulties, he said.
But Dr Murphy said the UK had a much more robust system for collating data on maternal deaths and the Republic should seek to emulate it. Maternal deaths would include deaths of women while pregnant or within six weeks of giving birth.