The World Health Organization estimates there are 140 million births per year. Each represents a unique pregnancy that requires careful medical monitoring of both mother and baby. Pregnancy complications can have serious immediate medical consequences, and some impact the health of both mother and baby in the long term.
Medical professionals want to learn how different pregnancy complications impact long-term heart health in mothers, so they can provide better healthcare after birth. For example, a previous study found women who gave birth to a baby born before 37 weeks of pregnancy had higher chances of developing heart disease. Researchers are particularly interested in heart disease, as it is a major cause of death in women worldwide.
A recent study by researchers in the USA investigated whether different pregnancy complications were linked to increased risk of heart disease. Specifically, the authors were interested in heart problems caused by narrowing or blockage of blood vessels, known as ischemic heart disease, which can cause life-threatening heart attacks.
The researchers wanted to follow the long-term heart health of mothers who had experienced pregnancy complications. However, beginning a study to monitor health over a lifetime would take a lifetime in itself. Instead, the authors studied anonymised medical records of over 2 million women in Sweden who had given birth between 1973 and 2015. This approach meant the researchers could search the records for pregnancy complications and any cases of ischemic heart disease.
The authors searched for 5 different pregnancy complications. The first two related to birth, including preterm delivery and low birth weight, defined as birth weight under the 10th percentile for gestational age. The last three concerned the health of the mother during pregnancy, including high blood sugar, known as gestational diabetes, high blood pressure, known as pre-eclampsia, and other blood pressure issues unrelated to pre-eclampsia.
Alongside pregnancy complications and ischemic heart problems, the authors noted other factors that could link to heart disease, including smoking and body mass index. The researchers used their compiled data to predict how each pregnancy complication impacted risk of ischemic heart disease, in comparison to women with healthy births. They used a statistical analysis called a Cox regression to build a model of incidences of ischemic heart disease over time depending on the presence of each pregnancy complication.
The researchers found 30% of women had experienced pregnancy complications, and nearly 4% of all women in the study had been diagnosed with ischemic heart disease later in life. The analysis showed all 5 complications were linked to a greater risk of heart disease, even when factors like smoking and body mass index were accounted for. Of all complications, women with blood pressure issues unrelated to pre-eclampsia showed the highest risk of ischemic heart disease. Women who had these blood pressure issues during pregnancy were twice as likely to develop ischemic heart disease within 10 years of delivery than those without pregnancy complications. Moreover, increased risk of heart disease was still detected even up to 46 years after delivery for all complications.
The researchers also investigated if women with more than one pregnancy complication had higher chances of developing heart disease. They found women who had given birth to a preterm baby and had experienced pre-eclampsia, gestational diabetes, or other blood pressure issues during pregnancy had an even greater risk of ischemic heart disease than those with only one complication.
The authors suggested two different ways to interpret a link between each of the 5 pregnancy complications and ischemic heart disease. First, they proposed pregnancy complications could cause bodily damage and contribute to the development of ischemic heart disease. Alternatively, they considered there could be a pre-existing risk for some women that predisposes them to both pregnancy complications and ischemic heart disease. The researchers stated further research into the genetics behind pregnancy complications and heart disease would help answer this question.
The authors also admitted the study had some limitations. For example, the medical records did not contain any information on diet and exercise, which are both strongly linked to heart disease. Nevertheless, the researchers argued the results of this study stressed that women who have experienced pregnancy complications should have regular medical check-ups to monitor heart health.