Placental insufficiency and fetal growth restriction lead to postnatal hypotension and altered postnatal growth in sheep

Low birth weight has been associated with elevated arterial pressure in lat er life but mechanisms are unknown. Our aim was to determine the effects of low birth weight resulting from intrauterine growth restriction (IUGR) on fetal and postnatal arterial pressures and the potential roles of circulati ng cortisol and renin. We induced IUGR by umbilico-placental embolization ( UPE) in fetal sheep from 120 d of gestation until birth (approximately 147 d); postnatal lambs (8 IUGR, 8 controls) were studied for 8 wk. Fetal and p ostnatal arterial pressures were measured and blood samples taken for measu rement of gas tensions, cortisol concentrations and renin activity. In IUGR fetuses, mean arterial pressure (MAP) initially increased with UPE, but ne ar term was not different to values in controls. IUGR lambs weighed 33% les s than controls at birth and remained lighter than controls during the 8 po stnatal weeks; their growth pattern was different to that of controls. IUGR lambs had lower MAP than controls, and this relative hypotension (-4 mm Hg ) persisted throughout the 8 postnatal weeks. Covariate analysis showed tha t the relative hypotension of IUGR lambs could have resulted from their sma ller size, Plasma cortisol concentrations were not different between IUGR a nd control animals before or after birth. Plasma renin activity was not dif ferent in postnatal IUGR lambs compared with controls. Thus, postnatal cort isol and renin levels were not consistent with the development of hypotensi on or hypertension. We conclude that late gestational IUGR in sheep leads t o relative hypotension in the early postnatal period, probably a result of reduced body size.