Birth weight and blood pressure in young adults

Background-The intrauterine environment may be a critical period for the de velopment of hypertension in later life. In the present study, we applied t he twin approach to estimate the contribution of genetic and environmental causes that may underlie the birth weight-adult blood pressure association. Methods and Results-Birth weights of 418 twin pairs were obtained prospecti vely, and resting and 24-hour ambulatory blood pressures were obtained at t he age of 18 to 34 years. In women, resting systolic blood pressure decreas ed 4.27 mm Hg (P <0.001) and diastolic pressure decreased 2.18 tnm Hg (P=0. 02) per kilogram increase in birth weight. Similar associations were found for ambulatory measurements, although these were somewhat less pronounced. Pair-wise analysis confirmed these findings: twin pairs of whom both member s had a low birth weight (< 2500 g) had a higher systolic blood pressure co mpared with twins who both had a high birth weight (greater than or equal t o 2500 g). Systolic blood pressure of the lightest of a low-birth-weight pa ir was greater than or equal to4.7 mm Hg (P=0.02) higher and of the heavies t greater than or equal to2.4 mm Hg higher (P=0.2) than similar measurement s in high-birth-weight pairs. Intrapair differences in blood pressure betwe en the lightest and the heaviest at birth were only present in low-birth-we ight pairs. The results were similar for monozygotic and dizygotic twin pai rs. In men, no associations were found between birth weight and adult blood pressure. Conclusions-These findings suggest that prenatal programming of adult blood pressure occurs at least in female twins. We suggest that particularly mat ernal influences, experienced by both twin members, may underlie the associ ation between birth weight and blood pressure. The fetoplacental unit seems to influence blood pressure only when both fetuses had low birth weight.