ObjectiveTo study whether heredity for hypertension influences intra-uterine growth and the relationship between fetal growth and adult blood pressure.DesignFive-year prospective follow-up study with retrospective collection of data on size at birth and gestational age from obstetric records.SettingCentre of preventive medicine in Malmö, Sweden.SubjectsThirty normotensive men with and 27 without heredity for hypertension were investigated in 1990, and the majority (n= 28 andn= 20, respectively) in 1995 also.Main outcome measuresTwo measures of intra-uterine growth were compared between the groups and related to adult systolic blood pressure: the birth weight deviation from the expected birth weight based on ultrasonically derived intra-uterine growth curves, and the degree of thinness at birth (ponderal index = weight/length3).ResultsThe birth weight deviation in men with heredity for hypertension differed significantly from that in men without such heredity (%) (−6.9 ± 12.0 versus +7.3 ± 18.4;P= 0.002). Ponderal index was somewhat lower in the men with than in those without heredity for hypertension, but the difference did not reach statistical significance (kg/m3) (25.9 ± 2.6 versus 27.0 ± 2.2;P= 0.08). In the group with heredity for hypertension, systolic blood pressure correlated inversely with ponderal index both in 1990 (r= −0.44;P= 0.01) and 1995 (r= −0.49;P= 0.009), and the 5-year increase in systolic blood pressure correlated inversely with the birth weight deviation (r= −0.38;P= 0.04). No such correlations were found in the group without heredity for hypertension.ConclusionOur results suggest that genetic factors contributing to the development of hypertension may influence intra-uterine growth.