Fetal oxytocin and its extended forms at term with and without labor.
OBJECTIVE
We examined the concentrations of oxytocin and extended forms of oxytocin in umbilical plasma with and without labor.


METHODS
Umbilical venous and arterial blood were sampled in 27 term fetuses delivered vaginally and 13 delivered abdominally before labor. Extended forms and oxytocin were measured by radioimmunoassay and compared by analysis of variance or t test.


RESULTS
Concentrations of extended forms were higher than oxytocin concentrations (24.7 +/- 3.1 vs 6.1 +/- 1.2 pg/ml, p < 0.01). Extended forms were higher in umbilical venous than in arterial plasma (29.6 +/- 5.0 vs 19.8 +/- 3.1 pg/ml, p < 0.05); oxytocin concentrations were not significantly different (4.7 +/- 1.6 vs 7.8 +/- 1.8 pg/ml). Concentrations of extended forms were markedly lower with than without labor (17.1 +/- 3.0 vs 37.1 +/- 5.7 pg/ml, p = 0.01). Ratios of extended forms over oxytocin decreased with labor.


CONCLUSIONS
In umbilical plasma extended forms of oxytocin are more abundant than oxytocin. Extended forms originate in the uterus and decrease markedly with labor.
Mueller-Heubach
E
E
Department of Obstetrics and Gynecology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, NC 27157-1066, USA.
Morris
M
M
Rose
J C
JC
D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D006801:Humans; D007743:Labor, Obstetric / Q000097:blood*; D010121:Oxytocin / Q000031:analogs & derivatives / Q000097:blood*; D011247:Pregnancy; D011863:Radioimmunoassay; D014469:Umbilical Arteries; D014471:Umbilical Veins
D010121:Oxytocin