Up-regulation of oxytocin receptor expression at term is related to maternal body mass index

The likelihood of cesarean is in part related to maternal body mass index (BMI). Myometrial changes may be responsible.

Myometrial biopsies were collected from the upper edge of the hysterotomy from women undergoing scheduled cesarean with term, singleton gestations. Oxytocin receptor and connexin-43 mRNA protein expression was quantified with real-time polymerase chain reaction and Western blot.

Twenty subjects were recruited: 13 repeat and 7 primary cesareans. Oxytocin receptor mRNA was associated with BMI among women undergoing primary (r = 0.75; p = 0.05) but not repeat cesarean (p > 0.05). Controlling for gestational age, this association strengthened (p = 0.004). Receptor protein expression showed a linear correlation with BMI in the primary cesarean group (p = 0.002). Connexin-43 mRNA expression was not related to BMI in women undergoing primary (r = -0.14, p = 0.76) or repeat (r = -0.01, p = 0.86) cesarean.

Oxytocin receptor, but not connexin-43, expression is related to BMI, suggesting an alteration in oxytocin receptor expression or function related to obesity.