Induction of Labour & Ripening of the Cervix: Mechanisms and methods
Bishop Score – based on:
• Cervical dilation
• Cervical effacement
• Cervical consistency
• Cervical position
• Station
Amniotic membranes
ruptured
IV artificial oxytocin administration
Stimulates Ca2+ release from intracellular stores in myometrium smooth muscle
Selected Indications for Induction of Labour
(Risk of continuing pregnancy > delivering)
Please refer to “Induction of labour: Indications and contraindications” slide
Bishop Score > 6
Cervix favorable
↑ Natural release of prostaglandins from uterine wall
Bishop Score 4-5
Proceed based on clinical picture
Amniotic membranes intact
Amniotomy to artificially rupture amniotic membranes
Rush of amniotic fluid
Bishop Score < 3 Cervix unfavorable and requires ripening Artificial prostaglandin into vagina (gel or vaginal insert) Ripening options Ripening balloon in cervix Pressure applied to internal and external cervical os Foley catheter in cervix Pressure applied to internal cervical os Act as calcium ionophores to áintracellular Ca2+ Activate EP1 and EP3 receptors on myometrial cells Lack of fluid cushion causes more fetal head engagement Fluid flow may carry umbilical cord with it Cord prolapse (if fetal head not engaged/ low enough in pelvis to block exit of cord) Degradation of collagen in the connective tissue stroma of cervix Cervix softens Cervical dilation Cervix stretches (until balloon falls out) Author: Lindey Felske Reviewers: Ran (Marissa) Zhang Brianna Ghali Ingrid Kristensen* * MD at time of publication Risk of uterine rupture (if prostaglandins used as a ripening method after previous C- section) Uterine contractions ↑ Myometrial contractility ↑ Pressure on cervix Labour If needed, proceed to amniotomy and/or oxytocin once cervix is favorable Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published July 4, 2022 on www.thecalgaryguide.com