An investigation into the causation of the onset of labor by parabiosis during pregnancy

Influence of Pregnant Parabiotic Partners on Time of Parturition in Rats

“…Earlier studies by Sauerbruch & Heyde (1910), Fels (1929) and Hill (1932) demonstrated that parturition is unaffected in a pregnant rat joined in parabiosis with a non-pregnant rat. Kross (1926) and Munemitsu & Segal (1959) reported no evidence of a disturbance in length of gestation or in parturition when two pregnant rats were placed in parabiosis. We reasoned that a humoral factor released as a stimulus to parturition in the rat might not cause the onset of parturition in its parabiotic partner unless the partner was near term.…”