Birth weight, hypertension and "white coat" hypertension: size at birth in relation to office and 24-h ambulatory blood pressure.

We investigated the association of size at birth with hypertensive status defined by office blood pressure (BP) and 24-h ambulatory BP monitoring in a historical cohort study of 736 men born 1920-1924 and examined at age 70 years. Office BP was measured after 10-min supine rest with a sphygmomanometer, ambulatory BP was recorded with Accutracker 2, and anthropometric and other measurements were taken at a clinic. Birth weight and gestational age were abstracted from the men's birth records. A total of 24% of the men were treated for hypertension at the time of the study. Among not treated subjects, there was a weak positive association of birth weight with daytime and 24-h diastolic ambulatory BP. In subjects treated for hypertension, both office and ambulatory BP were inversely related to birth weight, although these associations were not statistically significant. Birth weight did not show significant association with sustained hypertension (elevated office and daytime ambulatory BPs) but showed a strong and statistically significant inverse association with "white coat" hypertension (elevated office BP and normal daytime ambulatory BP) when adjusted for concurrent body mass index (odds ratios 1.91, 1.59, 1 and 1.21 from lowest to highest quartile of birth weight, P-value for trend 0.035). We conclude that BP measured by 24-h-ambulatory monitoring is not related to birth weight in a pattern previously reported for office BP and that factors related to growth in utero are particularly related to higher risk of "white coat" hypertension.