The lifespan of men and the shape of their placental surface at birth

Background: Tall men generally lead longer lives than short men. Within the Helsinki Birth Cohort, however, there is a group of boys among whom being tall when they entered school was associated with reduced lifespan. These boys had birthweights and maternal heights above the median for the cohort; but they tended to be lighter at birth than their mother's body mass index (weight/height(2)) in pregnancy predicted. We suggested that, while they had grown rapidly in utero, their growth had faltered at some point; and their tallness at age seven was the result of a resumption during infancy of their rapid growth trajectory. We here examine the size and shape of their placentas at birth to gain further insight into their path of fetal growth.

Methods: We examined all cause mortality in the 1217 men who had birthweights and maternal heights above the median for the cohort. Their birth measurements included placental weight and the length and breadth of the placental surface.

Results: Shorter length of the placental surface was associated with increased mortality (p = 0.002). There was no similar trend with the breadth. Mortality rose as the difference between the length and breadth decreased, that is as the surface became rounder. The hazard ratio was 1.10 (1.03-1.18, p = 0.007) for every cm decrease in the difference. Among men with a round placental surface (length-breadth difference 2 cm or less) increased mortality was associated with lower birthweight (p = 0.03 or 0.005 allowing for mother's body mass index) and shorter gestation, but not with lower head circumference or length.

Conclusion: Reduced lifespan among men is associated with a particular path of early growth. After rapid growth in early gestation, associated with tall maternal stature, soft tissue growth falters in mid-gestation. Rapid growth resumes in late gestation and continues through infancy.