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Developmental Biology - Heart Development
Predicting Heart Health In Infants
Birthweight and height determine future heart health...
A baby's proportionality at birth - measures of both birthweight and length - may tell doctors whether a child is born with a risk for heart problems later in life.
Birthweight only tells part of the story for potential fetal growth. The additional measure of infant length, gives a deeper picture of growth trajectory, explains Brian Stansfield MD, neonatologist, Medical College of Georgia (MCG) and Children's Hospital of Georgia at Augusta University. A measure called the 'ponderal index', PI, along with the more widely used body mass index, BMI, provide a more accurate indication of fetal growth and what's ahead for the baby, explains Stansfield who is the corresponding author of the study published in the journal Early Human Development.
The new study also indicates that a low PI or low BMI at birth, should be considered risk factors needing attention and intervention.
Historically, birthweight has been the focus of studies connecting early life to later health consequences. "When you look at birthweight alone, you are looking at a measure of a single point in time, which is a big problem when it comes to projections," explains Stansfield. It's known that perinatal growth is affected by numerous factors from genetics to environment. A mother's health and her smoking habit, nutrition and gestational diabetes — each has implications on her neonate's development. Animal and human studies have also associated low birthweight and heart problems with fetal death as well. So MCG investigators hypothesized a baby's PI or BMI at birth could provide much better indicators on heart development and future function than just birthweight.
Researchers found in a group of 379 healthy adolescents with a low 'ponderal index', that increases in infant height and/or weight were out of sync during development. These 2 measurements were associated with an increase in the size of the infant's main pumping chamber of the heart — the left ventricle, and considered a risk for future cardiovascular disease.
"What we are trying to do is understand how do we categorize these children at birth so that we know who to watch more closely and ideally intervene earlier to help offset some of these risks. We believe our findings are a call to pediatricians to be even more diligent in measuring and noting birthweight and length parameters," says Stansfield. But, they also are a call to adult primary care providers to be aware that this very early measure of height and weight can provide lifelong insight into an individual's risk of heart and other disease. Digital health records should help doctors and patients alike find and keep up with these early statistics — to ideally intervene before trouble begins.
Records tracking smoking, alcohol and drugs; eating habits; and safe exercise during pregnancy, collectively help to ensure a healthy environment for the developing fetus, Stansfield notes. Even the genetics a baby inherits can be altered for better or worse throughout its development.
In what appears to be the first study to do so, researchers looked at relationships between birthweight and birth BMI and PI and the structure and function of the left ventricle in the children born. Other measures such as the Tanner scale, which looks specifically at pubertal development; socioeconomic status; physical activity, with children wearing monitors to track physical movement for seven days, were all measured to establish child health.
Children with an upward trajectory in blood pressure had about a 30% likelihood they would become obese versus those with a downward trajectory, who have about a 5% likelihood.
There was also about a 40% increase in visceral adiposity - fat around the stomach and other organs inside the abdominal cavity, which is considered particularly unhealthy in adolescents with an upward versus a downward BMI trajectory. These children were also much more likely to have a higher systolic pressure - the top number of a blood pressure which indicates the pressure inside arteries when the heart is contracting.
While more work is needed, proportionality also may help identify babies who appear, at least at birth, to be headed toward good heart health, Stansfield adds.
Lab animal studies indicate that cardiac mass is mostly determined at birth. Production of heart cells or the cardiomyocytes that make up the heart, rapidly diminishes after birth. This indicates that to get larger, the heart cells you are born with have to enlarge — hypertrophy — which is not considered normal growth. Enlargement of the left ventricle typically results from the heart having to work too hard against, for example, high pressure inside blood vessels, and can result in heart failure.
MCG investigators reported last year in the journal Pediatric Research that fetal growth restriction in Guinea pigs suppresses production of cardiomyocytes and increased death of these cells, which leads to hypertrophy of cardiomyocytes and disruptions of other normal heart architecture. The risk of other chronic diseases like obesity and diabetes, also are linked to low birthweight. But, the cardiovascular system seems particularly impacted by perinatal growth.
By fetal week five, the baby's heart has begun to develop, and it's during this critical period of development that the heart is most at risk for birth defects from factors like alcohol consumption by the mother, and even some of her medicines.
Abstract
Highlights
• Poor in utero growth is positively associated with cardiovascular mortality.
• Proportionality, rather than birth weight, accurately reflects fetal growth.
• Low Ponderal index (PI) associates with intermediate risk factors for heart failure.
Background
Perinatal growth has important implications for cardiac development. Low birth weight is associated with cardiovascular (CV) events and mortality, and animal studies have shown that fetal growth restriction is associated with cardiac remodeling in the perinatal period leading to a permanent loss of cardiomyocyte endowment and compensatory hypertrophy.
Aims
To determine associations of birthweight (BW) and multiple proportionality indexes (body mass index (BMI); weight/length2 and Ponderal index (PI); weight/length3) at birth on one hand, with left ventricular (LV) structure and function during adolescence.
Subjects
379 healthy adolescents aged 14–18?years in Augusta, Georgia.
Outcome Measures
LV structure and function parameters, including intraventricular septal thickness in diastole (IVSd), LV internal dimension in diastole (LVIDd), LV internal diameter in systole (LVIDs), LV posterior wall thickness in diastole (LVPWd), relative wall thickness (RWT), midwall fractional shortening (MFS), and ejection fraction, were assessed by echocardiography.
Results
When associations of birthweight, birth BMI, and birth PI with LV structure and function parameters were separately evaluated with linear regression adjusting for age, sex, race, Tanner stage, socioeconomic status, and physical activity, significant positive associations of BW with LVIDd (P?=?0.004), birth BMI with LV mass index (P?=?0.01), and birth PI with IVSd (P?=?0.02), LVPWd (P?=?0.03), and LV mass index (P?=?0.002) were identified. When LV structure and function parameters were compared across PI tertiles, a significant U-shaped trend for LV mass index (Pquadratic?=?0.04) was identified.
Conclusions
Our adolescent data suggest that proportionality at birth may identify associations between perinatal growth and cardiac remodeling independent of birthweight alone.
Authors
Alexandra A. Sawyer, Norman K. Pollock, Bernard Gutin, Neal L. Weintraub and Brian K.Stansfield.
Acknowledgements
The research was supported by the National Institutes of Health, the American Heart Association and the U.S. Department of Defense.
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Aug 5 2019 Fetal Timeline Maternal Timeline News
 A new study indicates a low PI or low BMI at birth, should be considered a risk that needs attention and intervention. CREDIT Public Domain.
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Commons License.