Fetal oxytocin and its extended forms at term with and without labor

Labor appears to affect blood levels of preprocessed and completely processed oxytocin. Oxytocin stimulates uterine contractions and is made by the fetus and placenta as well as by the maternal pituitary. Blood samples were collected from the umbilical cord vein and artery immediately after vaginal birth in 26 women and after cesarean delivery prior to labor in 13 women. Overall, the preprocessed form predominated. However, the average concentration of preprocessed oxytocin was 37 picagrams per milliliter in infants delivered before labor versus 17 picagrams per milliliter in those delivered after labor. The concentration of processed oxytocin was 5 to 7 picagrams per milliliter in both groups.