The perinatal development of arterial pressure in sheep: effects of low birth weight due to twinning.

The aim of this study is to determine the effect of fetal growth restriction due to twinning on the perinatal development of arterial pressure. Arterial pressure was recorded in fetal sheep (5 singletons, 8 twins) during late gestation and at 8 weeks after birth (11 singletons, 18 twins). In fetuses, there were no differences between singletons and twins in arterial pressure or plasma electrolytes. Postnatal twins were 17.3% lighter than singletons at birth, and growth rate was similar to singletons up to 8 weeks. After birth, arterial pressure was not different between groups, except that at 8 weeks, the systolic pressure was lower in twins. After birth, there were no differences between twins and singleton lambs in concentrations of plasma electrolytes, plasma renin, angiotensin II, and cortisol. Taken together with previous findings, the authors conclude that natural twinning in sheep followed by normal postnatal growth does not lead to hypertension.