Preterm delivery is one of the five pregnancy complications that have been linked with an increased risk of ischaemic heart disease for the mother decades after delivery. — Filepic
Women who experience any of five major pregnancy complications, e.g. preterm birth and pre-eclampsia, show an increased risk of ischaemic heart disease up to 46 years after delivery, finds a study from Sweden published by The BMJ on Feb 1 (2023).
The researchers say all major adverse pregnancy outcomes should be recognised as lifelong risk factors for ischaemic heart disease and women should be offered appropriate care to help prevent its development.
Heart disease is a serious condition where the blood vessels supplying the heart are narrowed or blocked, and is the leading cause of death among women worldwide.
Adverse pregnancy outcomes have been linked with higher future risks of heart disease.
But although nearly a third of women experience an adverse pregnancy outcome during their reproductive years, few studies have examined more than one outcome in the same group of women, preventing any firm conclusions from being drawn.
To address this, researchers based in the United States and Sweden set out to examine the associations between five major adverse pregnancy outcomes and long-term risks of ischaemic heart disease in mothers.
They identified 2,195,266 women in Sweden with no history of heart disease who gave birth to a single live infant between 1973 and 2015 at an average age of 27.
Using nationwide medical records, they then tracked cases of ischaemic heart disease from delivery date to December 2018 (average follow-up time of 25 years, up to a maximum of 46 years).
The five major adverse pregnancy outcomes of interest were:
- Preterm delivery (less than 37 weeks gestation)
- Baby who was small for gestational age at birth
- Pre-eclampsia
- Other blood pressure disorders of pregnancy, and
- Gestational diabetes.
Other important factors were taken into account, such as the mother’s age, number of children, education level, income, body mass index (BMI), smoking habit, and history of high blood pressure, diabetes or high cholesterol.
Overall, ischaemic heart disease was diagnosed in 83,881 (3.8%) women at an average age of 58 years.
The results show that women who experienced any of the five major adverse pregnancy outcomes showed an increased risk of subsequent ischaemic heart disease.
For example, in the 10 years after delivery, after adjusting for all other factors, relative rates of ischaemic heart disease were increased by:
- Twofold in women with other hypertensive disorders of pregnancy (46 extra cases per 100,000 person years)
- 1.7-fold in those with preterm delivery (19 extra cases per 100,000)
- 1.5-fold in those with pre-eclampsia (12 extra cases per 100,000)
- 1.3-fold in those with gestational diabetes, and
- 1.1-fold in those who delivered a small-for-gestational age infant.
Women who experienced several adverse pregnancy outcomes showed further increases in risk.
In the 10 years after delivery, rates of ischaemic heart disease were:
- 1.3-fold with one adverse pregnancy outcome (20 extra cases per 100,000 person years)
- 1.8-fold with two adverse pregnancy outcomes (34 extra cases per 100,000), and
- 2.3-fold with three or more adverse pregnancy outcomes (58 extra cases per 100,000).
Most relative rates decreased over time, but remained significantly increased (1.1-fold to 1.5-fold) even 30-46 years after delivery, and were only partially explained by shared genetic or environmental factors within families.
This is an observational study, so it can’t establish cause, and the researchers can’t rule out the possibility that ischaemic heart disease was underreported or that unreported maternal smoking, obesity or other risk factors during pregnancy may have affected their results.
However, the large sample size based on highly complete nationwide birth and medical registry data and long-term follow-up prompt the researchers to say that all major adverse pregnancy outcomes should be recognised as lifelong risk factors for ischaemic heart disease.
“Women with adverse pregnancy outcomes should be considered for early preventive evaluation and long-term risk reduction to help prevent the development of ischaemic heart disease,” they conclude.
