Blood volume (BV), red cell mass (RCM; Cr-51) and plasma volume (125I-labeled albumin) were measured in 205 piglets from 28 litters shortly after birth. Spontaneous cord rupture in healthy piglets occurred during delivery (n= 25) or within 190 sec of birth (n= 82). Spontaneous and induced delay of cord rupture resulted hi a tune-dependent increase hi BV and RCM. BV (± S.D.) at birth was 72.5 ± 10.5 ml/kg (RCM, 23.6 ± 4.6 ml/kg) in the 25 piglets with prenatal cord rupture and 110.5 ± 12.9 ml/kg (RCM, 38.4 ± 7.0 ml/kg) hi 17 piglets with late spontaneous cord rupture. The mean blood volume of all the 107 healthy piglets with spontaneous cord rupture was 90.2 ± 12.7 ml/kg (RCM, 30.1 ± 4.8 ml/kg). RCM was significantly (P< 0.05) increased hi nine piglets with intra-uterine growth retardation (RCM, 35.8 ± 11.2 ml/kg) and hi 13 with metabolic acidosis but without signs of asphyxia (RCM, 35.8 ± 6.7 ml/kg). In five piglets with cord wrapping, prenatal cord rupture, and acute asphyxia, BV (57.8 ± 7.3 ml/kg) was significantly decreased. In five other piglets with prenatal cord rupture and acute asphyxia, BV (67.9 ± 10.0 ml/kg) corresponded to that of the normal piglets with prenatal cord rupture. However, delay of cord rupture to 60 sec after birth did not increase BV (66.0 ± 11.8 ml/kg) in four piglets with acute asphyxia. Forty-one premature piglets delivered 6 days before normal term had their cords ruptured prenatally or within 5 sec of birth. Their hematocrit at birth (0.337 ± 0.028 liters/liter) was significantly decreased compared to the normal full-term piglets with corresponding tune of cord rupture (0.384 ± 0.033 liters/liter). RCM in 18 piglets with prostaglandin-induced prematurity (18.9 ± 3.4 ml/kg) was significantly lower than hi 23 piglets whose births had been induced by ovarectomy of their mothers (RCM, 22.1 ± 3.2 ml/kg).SpeculationThere is a great variability of placental transfusion in piglets (average, 24%; range, 0 to 60% of fetal blood volume) because natural cord rupture occurred at any time from sub partu to 3 nun after birth. This implies that hypo- or hypervolemiaper se, hi the otherwise well adapted newborn, must not represent a pathologic condition. On the other hand, hi the newborn with abnormal adaptation to extra-uterine life, abnormal blood volume may be carefully considered as either cause or consequence of maladaptation requiring appropriate treatment.