Poor Growth in Womb
May Delay Maturation

Infants whose growth was restricted in the womb may show slower maturation of certain basic body functions, new research suggests.

Investigators at the University of Leicester in the UK say their findings could help explain why fetal growth restriction has been tied to high blood pressure and cardiovascular disease in adulthood.

The study of 192 infants found that those diagnosed with intrauterine growth retardation (IUGR) had higher nighttime heart rates and higher levels of the stress hormone cortisol than healthy infants did by the age of 21 weeks.

In IUGR infants, heart rate and cortisol patterns appeared to be slower to mature toward adult-like rhythms, Dr. J.A. Jackson and colleagues report in the Archives of Disease in Childhood.

The researchers speculate that these early differences in physiological development could help explain why some studies have found high blood pressure and heart disease to be more common among adults who were growth retarded as infants.

It's possible, they note, that the heart rate and cortisol differences seen in IUGR infants are the result of "fetal programing" that persists into adulthood.

IUGR is diagnosed when a newborn is significantly small for gestational age, the time-point in pregnancy when the baby is born. So a premature newborn, while typically small, would not necessarily be considered growth restricted.

Fetal growth restriction can result from a number of factors, such as poor maternal nutrition, certain medical conditions or infections in the mother, and defects related to the placenta or umbilical cord that hinder the supply of blood, oxygen and nutrients to the fetus.

A number of studies have suggested that factors in the womb may have long-term health effects. There's evidence, for example, tying low birth weight to a higher risk of cardiovascular disease decades later.

It's been suggested, Jackson's team notes, that adults who were growth-restricted infants may be at increased risk of high blood pressure and cardiovascular disease, and may have persistently high levels of cortisol.

"We speculate," they write, "that the early physiological changes seen in this study may well be the result of early fetal programing which persists into adulthood."

SOURCE: Archives of Disease in Childhood, January 2004.