Altogether we found 26 direct or indirect maternal deaths, giving a maternal death ratio of 8.7/100 000. This is twice as high as reported in official statistics. Hypertension during pregnancy was the main cause of death, followed by thromboembolism and mental illness. Our assessment is that suboptimal factors in medical care may possibly have contributed to half of the direct maternal deaths. In addition, suboptimal factors in medical care may have contributed to one-third of the indirect deaths.
Similar death patterns are reported by several European countries (3, 4, 6, 7). The results also correlate with previous studies in Norway (3, 8). Andersgaard and colleagues found a high rate of caesarian section among the direct deaths. Contrary to the results of our study, several deaths were attributed to complications arising during the operation and not to the underlying reason for the surgical procedure. In theory the majority of direct maternal deaths are unavoidable. Our study reveals that there is still a preponderance of direct deaths.
In line with Andersgaard and colleagues, we assessed that suboptimal factors in medical care may have contributed to a large proportion of the direct maternal deaths. In five of six deaths due to hypertensive disorders during pregnancy our assessment was that level 3 suboptimal factors were present, i.e. suboptimal factors may have contributed to the deaths, and different care or organisation could have prevented them.
Improving treatment of blood pressure is important. In 2006 the Royal College of Obstetricians and Gynaecologists recommended treating pregnant women with systolic blood pressure of > 150 – 160 mm Hg (9). These recommendations now also apply in Norway (10). Women with life-threatening high blood pressure must receive immediate help to reduce their blood pressure as fast as possible, and their response to the medication must be monitored.
In two out of four deaths due to thromboembolism we assessed suboptimal factors at level 3. More active screening to exclude pulmonary embolism in the case of breathing difficulties and chest pains in pregnancy or the postpartum period appears to be important. Postpartum haemorrhaging was a direct cause of death. In such cases adequate and timely treatment is decisive.
As far as we know, our study is the first to give an overview of indirect maternal deaths in Norway. Experience from the UK shows that the proportion of indirect deaths due to the aggravation of pre-existing diseases in women is increasing (4). There is much to indicate that we will experience the same development in Norway.
Mental illness was the most important indirect cause of death in our material, and this correlates with UK results (4). The finding gives food for thought and underlines a need to direct attention to mental disorders in pregnant women (11). In our view, deficient follow-up may have contributed to the deaths in our material. Previous experience of depression is a risk factor for postpartum depression, and as a rule depression already occurs during the pregnancy (12).
Experience from other countries shows that indirect deaths caused by cardiac diseases are on the increase (4). This type of disease was also one of the causes of death in our material, and suboptimal medical care may have contributed. However, we found no deaths attributable to complications resulting from congenital heart disorders – a factor which plays a key role in other countries (4).
Our results indicate that maternal mortality in Norway is on the same level as that reported in Denmark (9.4/100 000), somewhat higher than in Sweden (6.5/100 000), but lower than in the UK (11.3/100 000) and the Netherlands (10.8/100 000) (2, 4, 6, 7). In comparison the official maternal mortality ratio Norway reported to WHO was 4.7/100 000 for the same period.
In countries where the reporting of maternal deaths is based on the death certificate alone, WHO automatically multiplies the ratio by 1.5. However, our findings suggest that this is insufficient. The matching of registers in our study traced 11 of 12 deaths that did not appear in the official statistics. Similar findings have been made in other countries (1, 2, 4).
This shows that routine linking of birth and death registers combined with direct reporting from hospitals is a method that can give a more exact estimate of maternal mortality in Norway. We are of the opinion that linking registers combined with the introduction of a rubric in the death certificate where pregnancy in the previous year can be indicated will contribute to more accurate official statistics, particularly in the case of indirect maternal deaths.
Making the exact registration and auditing of maternal deaths possible should be a public administration responsibility. The regional ethics committee has given the Norwegian audit group for maternal deaths permission to continue the work as a research project up to 2025. Routine reviews will also facilitate the follow-up of the development over time.
Classifying causes of death is challenging. The professional expertise and broad composition of the audit group and its cooperation with other Nordic countries is a strength. Tracing cases by matching the Cause of Death register and the Medical Birth register has also proved to be a key factor. Both of these registers are almost complete.
Nevertheless we cannot rule out that some cases have not been registered. We can easily imagine that the risk of inadequate reporting of births increases when dramatic events occur. Incomplete death certificates may also have contributed to deficient registration. The relatively low number of deaths may have affected the cause of death pattern, but the finding that hypertensive complications are the main cause of death appears to be stable (3).