IDUCTION OF LABOUR
Induction Implies stimulation of contraction before the spontaneous onset of labor , with or without ruptured membranes.Augmentation refers to stimulation of spontaneous contraction that considered inadequate because of failed cervical dilatation and fetal descent.Indications of IOL Post datesFetal growth restrictionplacental insufficiency e.g. oligohydramniosPre-eclampsia& other maternal hypertensive disordersDeteriorating maternal illnessProlonged prelabour rupture of membranesUnexplained antepartum hemorrhageDiabetes mellitusTwin pregnancy beyond 38 weeksRhesus iso immunizationSocial reasons
Contraindicatios Transverse or oblique fetal lie Umbilical cord prolapse Previous classical uterine incision or transfundal uterine surgery (e.g. from myomectomy) Placenta or vasa previa Any contraindications to vaginal delivery, or indication for cesarean delivery
Uterine hypercontractility tachysystole (more than five contractions per ten minutes for at least 20 minutes)uterine hypersystole/hypertonus (a contraction lasting at least two minutes).
Modified Bishop Score This score is predicting for the succession of induction of labour. The total score is in the range of 0-13, Hihg scor(favourable cervix) associated with easier,shorter induction&less likely to fail. Cervical ripening is a process that occurs prior tolabor in which the cervix is softened, thinned, and dilated
Modified Bishop score >=5 3-4 1-2 0 Dilatation of cervix (cm) Soft Medium Firm Consistency of cervix <0.5 1-0.5 2-1 >2 Length of cervical canal (cm) Anterior Central Posterior Position of cervix +1 -1or 0 -2 -3 Station (cm above ischial spines) 0 1 2 3
Bishop cervical score A score of 6 or more predicts the likelihood of successful induction of labour. A score of 5 or less is regarded as being unfavourablefor induction of labour, and useof artificial ruptureof theamniotic sac and/or oxytocin infusion are unlikely to be successful. More recently, measurement of fibronectin in cervicovaginal secretions has been used to predict the immine nceof labour, with variablesucce ss.
Method of induction
mechanical methods Transcervical catheter Extra-amniotic saline infusion (EASI)Hygroscopic cervical dilatorsMembrane stripping amniotomyDisadvantages: Less efficient in inducing labour. More incidence of uterine trauma. Separation of a posteriorly situated placenta. Higher incidence of infection as ascending infection &Increase the risk of fetal infection including HIV& the procedure itself might place the fetus at increased risk of HIV if the skin of presenting part is scratched
5-AmniotomyRupturing the amniotic membranes through the cervix has been documented as a method of labour induction for over 200 years. Arise in prostaglandin metabolites. Amniotomy alone results in delivery within 24 hours in about two-thirds of cases.
Methods:Forewater (low) amniotomy: Stripping of the membranes is done first, then the forewater is ruptured by amnihook, toothed forceps or Kocher's forceps. Hindwater (high) amniotomy: The Drew-Smythe catheter is introduced between the membranes and uterine wall to a point above the presenting part.
Rupture of hind water
.This method has the advantage that the use of exogenous uterine stimulants, with the risk of uterine hyper-stimulation, is avoided, and the amniotic fluid may be observed.However, the procedure may be uncomfortable and it gives rise to the possibility of ascending infection. The majority of deliveries then occur within 12 hours.
Pharmacological techniques
Prostaglandine PG PGs are naturally occurring unsaturated fatty acids present in different body fluids and tissues as the seminal fluid, endometrium, amniotic fluid, lungs and brain. PGs are resulted from the action of PG synthetase enzyme on arachidonic acid.PGLabour induction with prostaglandin F2 alpha was introduced in the 1960s. Subsequently, formulations of prostaglandin E2 (PGE2, dinoprostone) were developed which largely replaced the use of F2 alpha. within 24 h than dinoprostone. The greater efficiency of misoprostol (E1)has been related to more rapid cervical Ripening
.Prostaglandins .Prostaglandins can be administered via many routes but the commonest are:In living foetus: Prostaglandin E2 vaginal tablet 3 mg (Prostin) is applied deep in the posterior fornix. A second tablet is applied 6-8 hours later if labour is not commenced. The maximum dose is 6 mg. Vaginal gel (PGE2 1-2 mg) may be more reliable. In dead foetus: Extra-amniotic and intra-amniotic prostaglandin F2α.
Obstetric Actions They induce ripening of the cervix and uterine contractions Ripening of the cervix: Natural and synthetic PGs can ripen the cervix at any stage in pregnancy by inducing collagen breakdown and tissue hydration. Initiation and/or stimulation of uterine contractions: at any stage of pregnancy.
vaginal PG recommended for both unfavourable and favourable cervices. If oxytocin is used after PGE2, 6 h should elapse after the last vaginal dose of PGE2 to reduce therisk of uterinehype rstimulation.
Routes of Administration Intramuscular: PGF2α 15-methyl (Prostin 15 M) 250m g/2 hours. Intravenous: PGF2α 0.25m g / minute. Oral: PGF2α (Prostin tablets 0.5 mg) 0.5-1 mg/ hour. Vaginal tablets: PGE2 3 mg. Vaginal gel: PGE2 1-2 mg. Endocervical gel: PGE2 0.5 mg. Extra-amniotic gel: PGE2 400-500m g. Intramyometrial: PGF2α 1 mg. Intra-amniotic and extra-amniotic PGF2α.Buccal or subligualRectal misoprostol
Complications Nausea. Vomiting. Diarrhoea. Flushing. Tachycardia. Pyrexia.
Contraindications Cardiac disease. Hypertension.Oxytocin Mode of action: It depolarises cell membrane potential and alter permeability to sodium. The maximal sensitivity to oxytocin is achieved by 34-36 weeks’ gestation.
Mode of Action Oxytocics act on the pregnant uterus within 1 minute if injected IV, within 2 minutes if injected IM and its action lasts for 30 minutes. These cause initiation and increase in frequency, strength and duration of uterine contractions. These are more effective with the advancement of pregnancy.
Indications Inevitable, incomplete and missed abortions. Induction of labour. Augmentation of labour. Evacuation of vesicular mole. Prophylaxis and treatment of postpartum haemorrhage. Contraction stress test.
Routes of Administration IV drip is the most common use. IV pump using an electronic pump: is the most accurate for calculation of the infused dosage. IM and IV bolus may be given postpartum. Direct intramyometrial: during caesarean section. Nasal spray: to help evacuation of the engorged breasts.
Contraindications Previous uterine scar as C.S, hysterotomy or open uterus metroplasty. Some malpresentations as shoulder and brow presentations. Foetal distress and placental insufficiency. Contracted pelvis. Grand multipara. 6-Incoordinate uterine actions.
Complications Rupture uterus. Foetal distress and asphyxia. Constriction ring and hypertonic inertia. Amniotic fluid embolism. Water intoxication due to its antidiuretic effect and the large amount of IV fluids when given as a drip. Coronary spasm if the crude posterior pituitary extract was used.
Because of the considerable variability in sensitivity of the myometrium to oxytocin, oxytocin is administered as a variable dose infusion, titrated against uterine contractions. The dose 1 mU/min, doubling the rate of infusion every 20–30minuntil adequate uterine contractions are achieved or a rate of 32 mU/min is reached. Once labour is established the infusion rate may be progressively reduced, as the myometrial sensitivity increases, to a rateof about 7 mU/min. Amniotomy should be avoided if the woman is not known to be free of infections such as HIV and hepatitis, in which case oxytocin infusion may be used with intact membranes
3- nitric oxide donors Isosorbide mononitrate induces cyclo-oxgenase 2 & induces cervical ultrastructure rearrangement similar to that seen with spontaneous cervical ripeningGlyceryl trinitrate4-mefepriston (an anti- progesterone)
Complications of IOL
Complications of IOL 1. hyponatremia2.failed induction3.uterine hyperstimulation 4.Fetal distress /hypoxia5.cord prolapse6.abruptio placenta7.uterine rupture8.inadvertant preterm labor9.hypotonic uterine post partum hemorrhage10.hyperbilirubinemia.Key point Castor oil, bath, and/or enemaCastor oil, bath and enema were a time-honoured methodof inducing labour. There is an association between castor oil, a cathartic, and meconium passage possibly by a direct effect on the fetal bowel.Other methodsFor the following methods of labour induction, thereis insufficient evidence either of effectiveness or of benefits over the methods outlined above:, oestrogens, corticosteroids,relaxin, hyaluronidase, acupuncture, breast stimulation,sexual intercourse, and homoeopathic methods.
ERGOT ALKALOID Ergometrine = MetherginActionIt induces sustained uterine contraction lasts for 3-4 hours.
Routes of Administration Onset of action Dose Route 7 minutes 1mg Oral 4 minutes 0.5 mg IM 1 minute 0.25 mg IV
Indications Inevitable and incomplete abortions. Prophylaxis and treatment of postpartum haemorrhage. Subinvolution of the uterus.contraindication Before delivery of the foetus as it will cause foetal asphyxia and rupture uterus. Cardiac disease. Hypertension.
Complications : In misuse only Rupture uterus. Constriction ring. Foetal asphyxia. Hypertension. Retained placenta.