Induction of Labour for Undergraduates Max Brinsmead MB

Induction of Labour for Undergraduates Max Brinsmead MB BS Ph. D September 2020

Definition n Triggering uterine activity that will… – Ripen the cervix – Dilate the cervix – Deliver the baby n Note that Augmentation of Labour refers to stimulation of uterine activity that has spontaneously commenced

When to induce labour: n When the risks of continuing the pregnancy outweigh the risks of induction – Maternal reasons – Fetal reasons

Indications for Induction of Labour n n n n n Prolonged pregnancy Ruptured membranes (at term) Maternal preeclampsia For maternal diabetes Fetus at Risk (IUGR or hypoxia) Fetal death (or lethal malformation) Chorioamnionitis Maternal request incl. SOBP Resources are optimal

How frequent is Induction of Labour? n If elective Caesarean section i. e. surgical delivery before the onset of labour, is included… n Then the incidence of IOL in contemporary obstetric practice exceeds 50% of all pregnancies

Agents for Induction of Labour n Mechanical Sweep the membranes n Amniotomy – forewaters or hindwaters n Foley catheter n Uterine massage n n n (Caesarean section) Pharmacological Oxytocin n Prostaglandins n

Sweeping the Membranes

Membrane Sweeping Should be offered prior to formal induction of labour n Is not associated with any increased risk of fetal or maternal infection n Is painful (patients should be warned) n Will reduce the need formal IOL for prolonged pregnancy if performed routinely at >40 w n

Amniotomy Tools - Amnihook

Amniotomy Tools - Amnicot

Amniotomy

Hindwater amniotomy tool The Drew-Smythe catheter

Foley catheter in the cervix

Cook Cervical Balloon System

Mechanism of action of the mechanical methods that induce labour n All act by the local generation of… n PROSTAGLANDINS (PGs) These 20 -carbon, 5 -ring eicosanoid fatty acids are autocrine and paracrine in action Found in many tissues and synthesized by most nucleated cells Fetal membranes and maternal uterine decidua are a rich source of several PGs that have TWO uterine effects n n n

The Uterine Effects of Prostaglandins n Ripening the cervix by: – Altering its connective tissue composition – Increasing its fluid content n n n This takes some time, >24 hours Effective at any gestation PGs also stimulate uterine smooth muscle to contract – This is referred to as its “oxytocic effect” – Can occur immediately n The half life of some PGs is milliseconds

Oxytocin n A classic hormone released from the posterior pituitary Neuro endocrine in its control It is a nonapeptide Closely related to Anti diuretic hormone (ADH) or Vasopressin Has roles in sexual bonding, orgasm, milk letdown and labour Syntocinon is the synthetic form of oxytocin n Has a half life of 2 hours in the circulation n n

Syntocinon in Use n n n n Administered only by IV infusion Typically begins with a low dose (1 m. U/min) Increase by doubling every 30 – 60 min according to the uterine response to a maximum of 32 m. U/min Not very effective before term because of absent receptors in myometrium Used to both induce and augment labour Not very effective when membranes are intact Used in high doses postpartum to contract the uterus and protect from PPH

Prostaglandins in Use n Best administered as a vagina gel or tape/pessary n – But can be injected directly into the myometrium of the uterus in the treatment of PPH – Or given per rectum “Prostin” is PGE 2 and comes in 1 mg & 2 mg doses n n n “Cervidil” is PGE 2 available as a tape in Australia “Cervagem” is gemeprost, a 1 mg pessary that is used to ripen the cervix or terminate pregnancy, causes fetal death in utero “Cytotec” is misoprostol that is used for TOP. Its oral use for induction of labour is controversial

Adverse Outcomes from Attempted Induction of Labour n Failed induction – May not have waited long enough or tried for long enough n “Fetal distress” – – – n n By causing uterine hypercontractility Cord compression FHR decelerations True fetal hypoxia is more common if there is placental compromise The need to monitor reduces maternal options Chorioamnionitis – A consequence of amniotomy and multiple vaginal exams n Cord prolapse during amniotomy – Will not occur if the head is “engaging” and filling the true pelvis

Less common outcomes from Attempted Induction of Labour n Increased risk of postpartum haemorrhage – Averted by high dose Syntocinon infusion after delivery n Uterine rupture – Mostly a problem after previous Caesarean n Amniotic fluid embolism – Syntocinon with intact membranes n Water intoxication (ADH effect of high dose n Abruption of the placenta Syntocinon) – Amniotomy with polyhydramnios n Fetal bleeding from vasa previa

Vasa Previa

How to induce labour: n n For prolonged pregnancy first sweep the membranes For ruptured membranes… Oxytocin by IV infusion n Although wait-and-see and vaginal PG’s are acceptable n n For all other patients (except those with a uterine scar)… Vaginal prostaglandins n Regardless of the state of the cervix or the parity of the patient n Amniotomy followed by oxytocin infusion 3 – 12 hours later is likely to be the most cost effective when the cervix is ripe n

Induction of labour after Previous Caesarean n For spontaneous labour the risk of scar rupture is 1: 200 With oxytocin infusion the risk is 1: 100 With prostaglandins the risk is 1: 40 More difficult to induce? n Direct effect of PG’s on connective tissue? n n Foley catheter is an acceptable alternative

Fetal surveillance during Induction of Labour n n Fetal wellbeing should be established prior to induction of labour. After vaginal prostaglandins check fetal wellbeing when contractions are detected or reported. Use CTG. If it is normal, and labour has been triggered, then intermittent monitoring can be used. But continuous CTG is required whenever oxytocin is infused

Hypercontractility with Oxytocin n If the CTG is suspicious or abnormal then stop the infusion If fetal compromise is suspected or confirmed, then deliver ASAP taking account the severity of CTG changes and relevant maternal factors – ideally within 30 min Or restart the oxytocin after not less than 60 min, at half dose and only if the CTG is normal

Using Prostaglandins The risk of hypercontractility with or without FHR changes is 1 -5% n Women should lie down for 30 min after PGs are inserted n Oxytocin should not be started within 6 hours of PG insertion n

Hypercontractility with PGs Remove any gel n Irrigation is not beneficial n Short term maternal O 2 may help n Uterine tocolysis with a betamimetic can be useful n

Induction of labour – a cautionary tale n n n n n Silvie age 28 was having her 1 st baby in 1995 The pregnancy went post term (>41 w) Admitted to hospital 6 pm and given 2 mg Prostin as a vaginal gel Established labour immediately and delivered by 9 pm i. e. not quite a precipitate delivery Baby could not swallow and required gastrostomy At 12 w Silvie very upset. “That baby was normal until you gave me that gel” The marriage dissolved I was awaiting the lawsuit But 6 months later the paediatrician told me that the baby had a major chromosomal abnormality

The 1 st recommendation of the RCOG concerning Induction of Labour Women must be able to make informed choices regarding their care with evidence-based information. n These choices should be recognized as an integral part of the decision-making process. n Give them a handout to reinforce this n

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