The Central Statistics Office (CSO) has only recorded one sixth of the known maternal deaths in Ireland last year.

According to the CSO's latest statistical report published at the weekend, there was only one maternal death in 2012, in the final quarter of the year, occurring in a woman aged between 25 and 34, in the final quarter.

This is believed to refer to the death of Savita Halappanavar in University Hospital Galway on October 28 last. The CSO refers to maternal deaths under the heading 'complications of pregnancy, childbirth and puerperium'.

However, at least five other maternal deaths are known to have taken place in 2012, none of which are recorded in the CSO report.

Cork University Maternity Hospital (CUMH) has already confirmed that it recorded three maternal deaths last year.

In addition, the Coombe Hospital in Dublin has confirmed that two mothers died in its care within 48 hours of each other last September.

In CUMH last year, one woman died in early pregnancy, another in late pregnancy, and a third post-natally. Two of the deaths are reported to have been the result of a pre-existing disease or a disease that developed during pregnancy, while the third was believed to have been due to direct obstetric complications.

At the Coombe, the two mothers died shortly after they had delivered their children by Caesarean section.

Statistics produced by the CSO on maternal deaths in Ireland rely on the official registration of deaths, which experts believe limits the definition of a maternal death, and has led to an under-reporting of the true maternal death rate.

Statistics published recently for the first time by the Maternal Death Enquiry-MDE Ireland system use wider criteria to define maternal death, These statistics showed that 25 pregnant women attending maternity units died between 2009 and 2011.

However, CSO statistics report that only six mothers died during this period.

While the CSO statistics claim only two maternal deaths took place nationally in 2011, the three Dublin maternity hospitals alone between them recorded six deaths during that year.

In the wake of the death of Savita Halappanavar last year, assurances were made by health authorities and the medical profession that in spite of this tragedy, Ireland still had one of the lowest maternal death rates in the world.

However, these assurances appear to have been based on the CSO statistics, which use more limited criteria for defining maternal mortality than the MDE Ireland stats.

The latter statistics show that while our maternal death rate is still low by international standards, it is higher than had previously been reported.

According to the latest MDE Ireland stats for 2009-11, our maternal death rate is 8 per 100,000 births, while the CSO stats record a figure of 4 per 100,000.

The MDE Ireland system for recording maternal deaths includes direct deaths from obstetric complications; 'indirect' deaths from previous existing diseases or diseases developing during pregnancy where the condition was aggravated by pregnancy; 'coincidental' deaths from unrelated causes that occurred during pregnancy; and 'late' deaths between 42 days and one year after termination, miscarriage or delivery that were the result of direct or indirect obstetric causes.

The MDE Ireland system is based on a similar system used in England and Wales, which is regarded as the 'gold standard' for maternal death reporting.