Hyperbilirubinaemia in Neonatal Rats after Oxytocin or Prostaglandin F_2α Treatment of Pregnant Rats

Abstract

Serum bilirubin concentrations were investigated in neonatal rats. High concentrations were found on day 1 falling to adult values by day 4. Oxytocin (500 IU/kg) given subcutaneously to the dams on day 22 of pregnancy increased bilirubin concentrations in neonatal rats. This dose of oxytocin shortened gestational length but increased the neonatal death rate. Oxytocin (500 IU/kg) also increased uterine contractions on day 22 of pregnancy, measured using intrauterine balloons inserted on day 19 of pregnancy. Rats delivered by Caesarian section at the same gestational age as the oxytocin-treated group did not exhibit hyperbilirubinaemia. Prostaglandin F_2α (300 μg/kg) administered intramuscularly on day 20 of pregnancy was found to advance parturition and produced a small rise in serum bilirubin concentrations in neonatal rats. The rat could serve as a model for investigating the mechanisms of neonatal hyperbilirubinaemia which has been suggested to occur after the use of oxytocin or prostaglandins in the human.