In a new study, scientists have found that women who gave birth before the 37th week of pregnancy are at an increased risk of developing ischemic heart disease over the course of their life independent of other risk factors such as BMI or smoking. These findings were published in the Journal of the American College of Cardiology.
These new findings suggest that women undergoing assessment for cardiovascular diseases should include their reproductive history when asked about related factors that might influence the assessment.
According to statistics, preterm delivery occurs in about 9.6 percent of births in the United States annually and is usually just like a normal birth that happens before the ideal period of gestation.
Previous research shows that preterm labor experienced by women can increase the chance of them developing hypertension, diabetes and hyperlipidemia. These factors in themselves are also risk factors for heart disease.
Though previous studies have shown associations between preterm delivery and future risks of heart disease, they have not shined a light on the long-term risks of heart disease for women across their life course and its variance by pregnancy duration.
— March of Dimes (@MarchofDimes) June 30, 2017
This is the first study to measure the potential influence of unmeasured familial (genetic and environmental) factors on associations between preterm delivery and future maternal risk of heart disease.
In order to conduct this research, the scientists took data from the Swedish Medical Birth Registry. This registry contains all prenatal and birth information for deliveries in Sweden. They collected all the data between 1973-2015. Then they studied 2,189,190 women who had single-birth deliveries during the assessment period.
Women with other women who had single-birth deliveries were also included in the assessment. Among all 1,188,730 women (54.3%) with at least one sister who had a single-birth delivery were included.
The pregnancy duration observed included six groups: extremely preterm (22-27 weeks), very preterm (28-33 weeks), late preterm (34-36 weeks), early term (37-38 weeks), full-term (39-41 weeks) and post-term (42 weeks or more). The first three groups were combined to provide summary risk estimates for preterm delivery during the study.
The data revealed that out of all, 49,955 (2.3%) women were diagnosed with heart disease. In the 10 years following delivery, women who delivered preterm or extremely preterm had 2.5 and 4-fold risks of heart disease, compared with those who delivered full-term, after taking out other factors of the equation like preeclampsia, diabetes, high BMI and smoking.
Early-term delivery also was associated with an increased risk of heart disease at 1.4-fold. Another observation showed that these risks subsequently declined but remained significantly elevated even 30-43 years after delivery.
When scientists analyzed data of women who were sisters, they found out that these findings were not attributable to shared genetic or environmental factors in families.
There are several aspects of the study that were limitations inhibiting its widescale adoption. These included the unavailability of detailed clinical data to verify heart disease diagnoses, the possibility that not all the co-factors could properly controlled like smoking, BMI etc., the data was only related to Swedish population and not many other ethnicities were involved, and the fact that heart disease diagnosis information used for the study wasn’t available until 2001, resulting in underreporting of the heart disease.
According to the experts, these study findings however do suggest that preterm delivery should now be recognized as an independent risk factor for heart disease across the life course of a woman.
Ischemic heart disease (IHD) is a condition of recurring chest pain or discomfort that occurs when a part of the heart does not receive enough blood. This condition occurs most often during exertion or excitement, when the heart requires greater blood flow. IHD can lead to a heart attack and stroke and increase chances of death from these events in women.