128: Observations on experimental intrauterine growth retardation in sheep

Abstract

Low birthweight in sheep is associated with increased perinatal mortality. The sheep uterus contains folds of endometrium (caruncles) which form the maternal cotyledon in pregnancy. Alexander (1964) removed caruncles & in a subsequent pregnancy observed a reduction of placental & fetal weight, increased incidence of premature labour & stillbirths. 4 small fetuses have been produced using this technique. Catheters were implanted into the ewe & the fetus between 105 & 110 d. Serial measurements of blood gases, pH, metabolites, cortisol & ACTH were made. The mean fetal carotid PaO2 & haematocrit were 15.9 ± 1.3 mm Hg & 37.4 ± 2.2% compared to 21.6 ± 1.0 mm Hg & 30.3 ± 0.6% in 7 control fetuses (P < 0.01). There were no significant changes in PaCO2 or pH. Plasma glucose (0.66 ± 0.03 μmol/ml), lactate (0.9 ± 0.02 μmol/ml) and a amino nitrogen (aNH2, 6.11 ± 0.25 μmol/ml) were lower than in control fetuses (glucose 1.19 ± 0.02 μmol/ml, lactate 1.47 ± 0.02 μmol/ml and a NH2 7.64 ± 0.02 μmol/ml)suggesting a limitation of placental transfer. We have previously observed increased ACTH with hypoxaemia or hypoglycaemia. However, the concentration of ACTH (69.2 ± 29.7 pg/ml) and cortisol (21 ± 8.2 ng/ml) in the small fetuses was not significantly different from controls.