Premature Birth 'Should Be New Risk Factor' for Cardiovascular Disease

December 10, 2012

OXFORD, United Kingdom— Young adults who were born preterm--on average at 30 weeks' gestation--have unique, adverse structural alterations to their heart that could put them at risk of cardiac problems, new research shows [1]. The study--which employed cardiac MRI--is the first of its kind to demonstrate such sequelae, say Adam J Lewandowski (John Radcliffe Hospital, Oxford, UK) and colleagues, who report their findings online December 5, 2012 in Circulation.

In an accompanying editorial [2], Dr Mikael Norman (Karolinska Institutet and University Hospital, Stockholm, Sweden) says the new findings are "pioneering [and] point at multiple, systemic, and long-standing effects after preterm birth that all may affect cardiovascular function, aging, and disease risk in later life."

Norman told heartwire : "A few generations ago, all people born preterm died. Now we have young adults born preterm--there are not yet any middle-aged people--whose parents would have been told by doctors, when the children were discharged in infancy, 'You don't have to worry anymore. Your baby was born preterm but is now perfectly healthy.' " This new research shows otherwise, he says. "I think there should be a recommendation that preterm birth is a new risk factor for cardiovascular events."

The implications of this work are that young adults born prematurely, particularly those born very preterm--defined as less than 32 weeks' gestation--should now be followed up into adulthood, Norman says. For those born moderately preterm (32 to <37 weeks' gestation), more research is required, he says, noting that this population is much larger, currently standing at around 13 million children each year worldwide.

Severity of Cardiac Structural Changes Graded According to Prematurity

Lewandowski and colleagues performed cardiac MRI on 234 individuals aged 20 to 39 years, 102 of whom had been followed prospectively since preterm birth (mean gestational age 30.3 weeks, birth weight 1.3 kg) and 132 of whom were born at term to uncomplicated pregnancies.

Those born preterm had significantly increased LV mass (66.5 g/m2 compared with 55.45 g/m2, p<0.001) with greater prematurity associated with greater mass. Preterm-born people also had short left ventricles with small internal diameters and a displaced apex. Ejection fraction was preserved, but both longitudinal systolic and diastolic function, as well as rotational movement, were significantly reduced among the premature individuals.

They also investigated whether key perinatal factors associated with preterm birth, such as maternal preeclampsia, growth restriction, and variation in postnatal weight gain, had additional impacts on the left ventricle relevant to adult cardiovascular health. They found that one, maternal preeclampsia, was associated with further reductions in LV systolic strain.

"This study demonstrates for the first time that young adults born preterm have a unique adverse LV structure and function," they observe. Furthermore, the severity of changes graded according to prematurity, they point out.

"Significant" Changes Could Cause Cardiac Events and HF in Middle Age

Norman told heartwire that the changes in the heart of the premature-born adults in this study "correspond to those seen in young adults who have an increase in body-mass index [BMI] of 9 to 10, so that is like going from a BMI of 25 to 35; it's quite a significant change. The worry is that this will have clinical significance later on in middle age, in the form of cardiac events and heart failure."

It's quite a significant change. The worry is that this will have clinical significance later on in middle age, in the form of cardiac events and heart failure.

He says other groups, including his own, have already demonstrated that people born prematurely have vascular problems--for example, "the vascular tree is not fully developed; it's smaller and narrower if you are born preterm." And hypertension is already known to be a problem in such people too, he adds, noting that BP is the most extensively studied outcome in relation to preterm birth.

"The combination of hypertension, smaller and narrower arteries and a heart that is remodeled is not a good one," he observed.

At present, says Norman, there are recommendations from the American Pediatric Society that children born preterm or small for birthdate should have their blood pressure checked during childhood, "but there is no recommendation about cardiac follow-up."

Could Perinatal Interventions to Limit Variations in LV Modeling Work?

Lewandowski et al say their results likely have far-reaching clinical implications. "With the first generation of very preterm-born survivors now reaching young adulthood, our findings are of considerable public-health interest," they state.

The combination of hypertension, smaller and narrower arteries and a heart that is remodeled is not a good one.

Norman concurs. "The most obvious clinical implication of this new knowledge is that young people born very preterm need continued and tailored follow-up, taking the total CV risk factor burden into account." Coming studies will disclose whether this recommendation is also valid for the four- to five-times larger group of adults born moderately preterm, he adds.

Both Norman and Lewandowski et al say that there could be selected perinatal interventions that could improve cardiovascular outcomes in young adults born prematurely. For example, improved neonatal nutrition or lifestyle intervention in young adulthood might help optimize cardiac health, they say.

Lewandowski et al have no conflicts of interest, nor does Norman.