Saving Mothers' Lives: - Public Health Agency for Northern Ireland

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9 Cardiac disease
Interpreting trends in deaths from myocardial infarction
There appears to have been an increase over the past three triennia in rates of death from ischaemic
heart disease. In 2003-5 eight women died from myocardial infarction due to ischaemic heart disease and
another four from ischaemic heart disease without demonstrable myocardial infarction. From the table it
appears that increasing deaths from ischaemic heart disease have contributed to this, although numbers
are small.
Table 9.3
Deaths from myocardial infarction, numbers and rates per 100,000 maternities; United Kingdom: 1985-2005.
Triennium Ischaemic Dissection Embolism Undetermined Total Rate 95 per cent CI
1997-1999 5 0 0 0 5 0.24 0.10 0.55
2000-2002 3 5 0 0 8 0.40 0.20 0.79
2003-2005 8 1 1 2 12 0.57 0.32 0.99
In considering factors which may have contributed to this rise, it is relevant to consider death rates among
women in the general population, shown in Table 9.4.
Table 9.4
Death rates per 100,000 population from myocardial infarction among women of childbearing age;
United Kingdom: 2000-05.
Age, years
15-24 25-34 35-44
2000-02 0.11 0.44 2.42
2003-05 0.05 0.38 1.98
Source: ONS, General Register Offi ce Scotland, General Register Offi ce Northern Ireland.
Although age specifi c rates have declined slightly between the past two triennia, the most striking feature
is the higher mortality among older women of childbearing age. As shown in Chapter 1, the percentage of
maternities in the United Kingdom which were women aged 35-39, rose from 12.3 per cent in 1997-1999
to 15.9 per cent in 2003-05 and the percentages of maternities to women aged 40 and over rose from 2.1
per cent to 3.2 per cent. The mean age of the women dying from ischaemic heart disease associated with
pregnancy in 2003-5 in the UK was 35. Similar patterns were shown in two studies of myocardial infarction
in pregnancy in the United States.
A study of 151 women with acute myocardial infarction in association with pregnancy from California
has demonstrated an overall incidence rate of 1 in 35,700 but the incidence of myocardial infarction in
pregnancy increased throughout the 1990s 6 . The maternal mortality rate was 7.3% in this group of women.
This study also demonstrated an increased risk related to maternal age. Women with an acute myocardial
infarction associated with pregnancy were more likely to be older compared with women who did not have
an acute myocardial infarction. Thirty per cent of those with an acute myocardial infarction were older than
35 years compared to ten per cent without.
A recent nationwide series of 859 cases of myocardial infarction in pregnancy from the US 7 found a rate of
6.2 per 100,000 deliveries (95% confi dence interval 3.0, 9.4). Although acute myocardial infarction is a rare
event in women of reproductive age, this study found pregnancy to increase the risk three- to four-fold. The
case fatality rate was 5.1%. The odds of acute myocardial infarction were 30-fold higher for women aged 40
years and older than for women less than 20 years of age. Other signifi cant risk factors were pre-existing
hypertension, thrombophilia, diabetes mellitus, smoking, blood transfusion and postpartum infection.