Induction of Labor Professor Hassan Nasrat
Physiological Background In Normal Pregnancy There Is A Dynamic Balance Between The Factors Responsible For Uterine Quiescence And Those Responsible For Uterine Contractility.
The Uterus • Factors Are Responsible For “Uterine Quiescence”: • A Higher Balance Of Progesterone To Estrogen Hormones. • Low Prostaglandins Activity. • Uterine Insensitivity To Oxytocin • LackOf The Gap Junction Between Uterine Muscle Fibers Which Are Essential For Coordinated Synchronized Contractions.
The Cervix Throughout pregnancy the cervix must remain firm and closed, with very little change until labor begin. Histologically the cervix is poor in smooth muscle (average 10% to 15%), its distribution tapers off along the cervix.
Cervical Ripening: Is A Complex Process That Involves A Series Of Anatomical And Physiological Changes In The Properties Of The Cervix. It Eventually Change It From A Firm, Long Structure Into A Soft And Short One That Permits Cervical Dilatation Concurrent With Uterine Contractions.
The Factors Responsible For Initiation Of The Ripening Process Are Not Fully Understood: • Change In The Estrogen To Progesterone Ratio Has Been Suggested. • Estrogen Can Promote Cervical Ripening By Up Regulating Collagenase. • Prostaglandins Play An Important Role In Cervical Ripening.
Assessment of cervical ripening Modified Bishop score • (blue Circles) Score of 3 (not suitable for induction) • (Red Circles) Score of 6 (suitable for induction)
Assessment of cervical ripening Table12-1: The Burnett Scoring System (or Modified Bishop score) (1966)
Induction of labor A Therapeutic Intervention That Aims To Initiate Uterine Contractions, With An Objective Of Achieving Vaginal Delivery. It Is Therapeutic Intervention that Should Have Clear Indications That Outweigh Any Potential Complications.
Indications For Induction Of Labor • The Continuing The Pregnancy Is Believed To Be Associated With Greater Maternal Or Fetal Risks Than The Risks Associated With Induction Of Labor. • There Is No Contraindication To Vaginal Birth
Methods Of Ripening The Cervix And Induction Of Labor • The Following Should be Reviewed: • The Indication (s) For Induction: This Should Be Strong Enough To Justify The Intervention, Including The Risk That Induction Might Fail And End In Cesarean Delivery. • The Condition Of The Cervix: Whether The Cervix Is Favorable Or Unfavorable.
Methods of induction of labor “IOL” • Amniotomy. • Oxytocin. • Prostaglandin compounds: PGE2 and F2-α and prostaglandin analogue, particularly Misoprostol
Amniotomy • Advantage: • Accelerate Uterine Contractions Through An Increase In The Release Of Local Secretion Of Endogenous Prostaglandin. • Permits Better Monitoring Of Fetal Status Using Scalp Electrode Electronic Fetal Monitoring. • It Reveals The Color Of The Amniotic Fluid If It Is Clear Or Stained With Meconium. • Allows Placement Of Intrauterine Catheter For Monitoring Of Uterine Contractions. The Technique And The Criteria That Should Be Checked Before ARM. The Amniohook Appears On The Right.
Potential Complications Of Amniotomy • Cord Prolapse: • Infection: • Abruptio Placenta: • Fetal Hemorrhage: Amniotomy Is Contraindicated In Patients With Known HIV, Or Active Herpes Virus Infections
Effects Of Oxytocin: • The Myoepithelial Cells Of The Breast, Which Surround The Alveoli Of The Mammary Gland, And The Smooth Muscle Cells Of The Uterus. • It Produces: Milk Ejection Effect. • Stimulates Periodic Contraction Of Uterine Smooth Muscle Cells Through A) Direct Interaction With Myometrial Receptors And • B) Indirectly By Stimulation Of The Release Of Prostaglandin E2 And F2-α In Fetal Membrane Through Activation Of Phospholipase C.
The Concentration Of Oxytocin Receptors Changes During Gestation By About 13 To 17 Weeks, The Concentration Of Oxytocin Receptors Is About Six Times Higher Than The Non-pregnant Level, And At The End Of Pregnancy It Is About 80 Folds Higher, Reaching Maximum Level At The Onset Of Labor Whether Full Term Or Preterm. • Also, The Distribution Of Oxytocin Receptors Within The Uterus Occurs In Such A Way That It Is Highest Around The Uterine Fundus And Tapers Off To Become Very Low In The Cervical Tissue. • TheUterus Is Insensitive To The Uterotonic Effect Of Oxytocin Until Substantial OxytocinReceptor Concentrations Are Induced. • Also, Because Receptors Are Spare In The Human Cervix, Oxytocin Alone Has No Direct Effect On Cervical Ripening
Preparation And Routes Of Administration For The Purpose Of Induction Of Labor With A Viable Fetus, The Only Acceptable Route Of Administration Of Syntocinon Is By Continuous Intravenous Infusion. This Permits Constant Blood Levels And Tight Titration Of Uterine Activity To The Infused Oxytocin Concentration. The Principle Is That The Dose And Infusion Rate Should Be Titrated To The Uterine Response And Fetal Condition.
The table shows different regiments for starting oxytocin infusions. No evidences that one regiment better than the other. Factors such as condition of the cervix, body surface area, gestational age can affect the regiment and dose of oxytocin.
Prostaglandin (Dinoprostone) PGE2 Route of prostaglandin administration: orally, intravenously, intravaginally, and intracervically. Currently it given via vaginal route asprostaglandin gel (Dinoprostone) 1 or 2 mg and prostaglandin tablets 3 mg. More recently, controlled release prostaglandin system has been introduced to the market. • Dinorprostone (PGE) vaginal insert • Prostaglandin is commonly used for cervical ripening, but there is no such dose for ripening and dose for induction. Therefore any patient who starts with the intention of cervical ripening is potentially in labor.
Misoprostol: • A prostaglandin E1 analogue that has the advantages over Dinoprostone of being: • Less expensive. • Stable in room temperature. • The drug may be given vaginally or orally, but the appropriate dose for either route is not yet determined.
Patient Pre-induction preparation and Management • Patient Counseling. • The Medical And Obstetric History Should Be Reviewed. • Contraindication For Induction Should Be Sought And Ruled Out. • The Readiness Of The Cervix (Bishop Score) • Gestational Age And Fetal Pulmonary Maturity. • The Presumed Ability Of The Fetus To Tolerate Labor: E.G. Cases Of Severe FGR May Not Tolerate Vaginal Delivery And Will Have A Better Outcome By Cesarean Section. • Maternal Condition: E.G. Cardiac Cases May Not Tolerate Prolonged Labor.
Patient Pre-induction preparation and Management • All induced patients should be managed in the labor room with continuous monitoring for uterine contractions and fetal heart. • Labor data, including cervical dilatation, should be plotted on partogram. • Since induced patients are expected to have longer periods of latent and active phases of labor, which should be acceptable as long as fetal and maternal conditions permit.
Untoward effects and complications of induction of labor • Prolonged labor and its physical and psychological consequences; • Increased rate of fetal distress: • Increased rate of instrumental delivery: • Uterine hyperstimulation and fetal distress: • Uterine Rupture.
Uterine HyperstimulationIs Defined As Contractions Frequency More Often Than Every 2 Minutes Or Contraction Duration Longer Than 90 Seconds With Or Without Fetal Heart Rate Changes. • Management Of Uterine Hyperstimulation: • Oxytocin Infusion Should Immediately Be Decreased Or Discontinued. • Intrauterine Fetal Resuscitation Should Be Initiated. • Oxygen Administration, Positioning The Mother On Her Left Side, Intravenous Fluid (If Not Contraindicated). • Tocolytic Such As Intravenous Terbutaline 0.125 Mg May Be Used. • In Some Cases, An Emergency Cesarean Section Has To Be Undertaken Due To Persistent Fetal Distress.
Specific Complications Related To The Agent Used For Induction: Prostaglandins: Particularly If Given Orally Cause Nausea, Vomiting, Diarrhea And Pyrexia. Oxytocin:May Be Associated With The Following Side Effects: A) Direct Vascular And Smooth Muscle Relaxation, Hence The Association Of Prolonged Oxytocin Administration With Postpartum Hemorrhage B) Antidiuretic Effect: The Use Of Large Doses Or In The Presence Of Excessive Intravenous Fluid Administration Can Result In Water Intoxication. C) Neonatal HyperbilirubinemiaAnd Jaundice Have Also Been Associated With The Use Of Oxytocin, More Commonly With Preterm Fetuses.