The surface area of the placenta and hypertension in the offspring in later life
Original Article | Published: 14 October 2009
David J.P. Barker*,1,2, Kent L. Thornburg2, Clive Osmond1, Eero Kajantie3,4 and Johan G. Eriksson3, 5-8
1MRC Epidemiology Resource Centre (University of Southampton), Southampton General Hospital, Southampton, UK, 2Heart Research Center, Oregon Health and Science University, Portland, OR, USA, 3National Institute for Health and Welfare, Department of Chronic Disease Prevention, Helsinki, Finland, 4Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki, Finland, 5University of Helsinki, Department of General Practice and Primary Health Care, Helsinginyliopisto, Finland, 6Vasa Central Hospital, Vasa, Finland, 7Folkhälsan Research Centre, Helsinki, Helsingfors Universitet, Finland and 8Unit of General Practice, Helsinki University Central Hospital, Finland
Hypertension is more common among people who had low birthweight. Birthweight depends on the mother’s body size and on the growth of the placenta. We studied a group of 2003 subjects, of whom 644 were being treated for hypertension. They were born during 1934-44 in a hospital that kept detailed records of maternal and placental size. Hypertension was associated with reduced placental weight and surface area. These associations were strongest in the offspring of mothers with below average height or low socioeconomic status. In people whose mothers had below average height (160 cm) the prevalence of hypertension fell from 38% if the placental area was 200 cm2 or less to 21% if the area was more than 320 cm2 (p=0.0007). In the offspring of tall, middle class mothers, who were likely to have been the best nourished, hypertension was predicted by large placental weight in relation to birthweight. The odds ratio rose from 1.0 if the ratio of placental weight to birthweight was 0.17 or less to 1.9 (95% confidence interval 0.8 to 5.0) if the ratio was more than 0.21 (p for trend =0.03). We conclude that the effects of placental area on hypertension depend on the mother’s nutritional state. Poor maternal nutrition may compound the adverse effects of small placental size. In better-nourished mothers the placental surface may expand to compensate for fetal undernutrition. Growth along the minor axis of the surface may be more nutritionally sensitive than growth along the major axis.