Cardiovascular disease (CVD)
describes any disease that affects the heart or blood vessels, and is
currently the leading cause of death in women world-wide. Now complications
during pregnancy can be used as an early indicator to identify women at high
risk of future cardiovascular disease. Pregnancy provides a window into early
adult female health, which can flag women at high risk of future ill health and
may allow treatments to be targeted early to those who need it most. In this
way CVD could be delayed or even prevented, suggest researchers who have looked
at the relationship between pregnancy complications and future disease.

Earlier studies support a link between common
complications during pregnancy and increased risk of CVD in later life. Women
with a history of pregnancy
related diabetes or pregnancy hypertension, pre-term
delivery (i.e. before 37 weeks), or those bearing a low or high birth weight child, are more likely to
develop future CVD. But whether
these four complications independently predict risk of future disease, or
whether one or a combination of pregnancy complications are better predictors
of future health is unclear. For example, are a mother’s chances of developing
future heart disease best predicted by a history of a specific complication,
say pregnancy diabetes, or by a combination of complications, such as pregnancy
diabetes and hypertension? This is important to figure out in order to establish
whether similar pathways to CVD exist, which may provide opportunities to treat
and stop disease.

Paths
to disease
Debbie Lawlor and colleagues at the University
of Bristol and University of Glasgow
got around these pitfalls by studying the effects of all four pregnancy
complications together on a range of CVD risk factors. CVD risk factors are
known indicators of future increased CVD risk and include high blood glucose,
insulin and fatty materials. Lawlor’s team looked at the pregnancy history of a
large population of 3,416 mothers who also had key CVD risk factors measured an
average of 18 years after pregnancy. Using statistical tools, a range of
factors, or confounders, that could be alternative explanations for the link
between pregnancy complications and CVD risk were also taken into account by
Lawlor’s team; namely smoking, a mother’s education level and body mass. For
example, smoking during pregnancy can increase CVD risk and also lead to a low
birth weight child. So, taking smoking and other important confounders into
account, allows true associations to be separated from those that are false.

Of the four pregnancy complications examined, pregnancy diabetes and
hypertension were the best independent predictors of future CVD risk. Mothers with
a history of pregnancy diabetes, were more likely to have raised blood glucose
and insulin compared to healthy mothers some 18 years after pregnancy. Women
with a history of pregnancy hypertension had a higher chance of having
increased insulin and unhealthy fat (cholesterol and triglycerides) later in
life, compared to their healthy counterparts. These associations did not change
when statistical tools took account of all pregnancy complications and
important confounders together, suggesting both pregnancy diabetes and
hypertension are independent risk factors for CVD. The fact that different CVD
risk factors associated with pregnancy diabetes as against hypertension, also
suggests that there are different disease pathways linking these two pregnancy
complications to CVD.

What about
the effect of pregnancy complications on future CVD, rather than simply CVD
risk factor levels? As the actual rate of CVD in this population was low,
reflecting the relatively young age of the women, a well known ‘scoring system’
was used to estimate future CVD risk based on all the measured CVD risk factors
combined. Using this approach Lawlor’s team found that, compared to healthy
women, those suffering from pregnancy diabetes or pregnancy hypertension are
23% and 27% more likely to have a CVD event in the next 10 years, respectively.
These findings held even when all pregnancy complications and confounders were
taken into account together, further supporting a role for both complications
as important predictors of future CVD risk.

Pregnant promises
“The
stress test of pregnancy provides a glimpse into the otherwise silent early
adult years in which chronic disease trajectories are set”, says Ellen Seely¹
who specialises in cardiovascular diseases in women at Harvard. She says
further investigation into the contribution of pregnancy complications to CVD
is needed to fully understand, and benefit from, the early warning system
pregnancy provides for predicting future health. Opportunities to screen during
pregnancy and intervene in high risk women early to slow or stop disease
progression could be on the horizon.

1Rich-Edwards, J. W., McElrath, T., McElrath, T., Karumanchi, A. and Seely, E. W. Breathing life into the lifecourse approach:Pregnancy history and cardiovascular disease in women. Hypertension (2010) 56(3), 331–334

This entry describes research published in the following article, selected by the Medical Research Council:

Associations of pregnancy complications with calculated CVD risk and cardiovascular risk factors in middle age: The Avon Longitudinal Study of Parents and Children