Abstract 092: Low Birth Weight per se Is Not a Determinant of Vascular Dysfunction and Presumably Future Cardiovascular Risk in Humans

Abstract

Background: Epidemiological studies suggest that low birth weight (BW) is associated with systemic vascular dysfunction and premature cardiovascular morbidity and mortality later in life. However, this association could be due to confounding factors associated with low BW, such as genetic factors, pathological events during intrauterine life, and maternal or early-life environmental insults. Studies of monozygotic twins born with significantly different BW provide a unique opportunity to control for these potential confounding factors, thereby allowing to directly study the effect of low BW per se on systemic vascular function later in life. Methods: We, therefore, measured flow-mediated dilation (FMD) of the brachial artery, carotid-femoral pulse wave velocity (PWV) and carotid intima-media thickness (IMT) in 13 monozygotic, monochorionic healthy twins pairs (mean±SD age, 13.5±3.4 years) who were born with significantly different BW (defined as >20% BW difference within pairs, 2310±600 vs. 1800±520 g, P<0.0001) and in 26 healthy age- and sex-matched control subjects born at term with normal BW (3460±360 g). None of the participants had suffered from intrauterine or perinatal complications. Results: The major new findings were two fold; 1) systemic vascular function was comparable in low and high BW twins (FMD, 9.0±1.8 vs. 8.7±2.0%; PWV, 6.5±1.3 vs. 6.6±0.9 m/s; IMT, 390±30 vs. 390±20μm, all P values >0.2, low vs. high BW) and 2) systemic vascular function in twins was similar to the one observed in control singletons (FMD, 8.8±1.3 vs.8.9±1.8%, P=0.95; PWV: 6.5±1.1 vs. 6.6±1.2 m/s, P=0.80; IMT: 390±25 vs. 385±20μm, P=0.33, singletons vs. twins). Finally, there existed no relationship between BW and vascular function in the whole study population (FMD: r=0.001, P=0.99). Conclusions: This study provides the first direct evidence in humans that low BW per se is not a determinant of systemic vascular dysfunction (and presumably future cardiovascular risk). Moreover, it indicates that independent of BW, vascular function in twins is normal. We suggest that the association between low BW and increased cardiovascular risk reported in earlier epidemiological studies was related to confounding factors associated with low BW.