Post-dated Pregnancy & Induction Of Labor

1. Post-dated Pregnancy &Induction Of Labor

2. Post-term Pregnancy (Syn:Post-dated Pregnancy or Post maturity Prolonged pregnancy) • A pregnancy that has reached or surpassed 42 weeks ( 294 days ) of gestation from the first day of the last menstrual period. ( ACOG,WHO,FIGO) • Incidence- Range 4-19%,Average incidence-10%

3. Aetiology • Wrong dates- The most common cause of prolonged pregnancy, due to inaccurate LMP • Hereditary- postdatism seems to run in families, showing a genetic predisposition • H/o previous prolonged pregnancy- recurrence 50%

4. Abnormal fetal HPA and adrenal hypoplasia as in anencephaly deficiency of dehydro-epiandrosterone reduced fetal cortisol response. • Placental Salphatase deficiency- this enzyme play a critical role in synthesis of placental estrogens which are necessary for the expression of oxytocin & PG receptors in myometrial cells

5. Changes associated with prolonged pregnancy • A series of changes occur in -amniotic fluid -placenta and - fetus Amniotic Fluid Changes • In Postdated Pregnancy quantitative &qalitative changes occur in Amniotic fluid

6. Quantitative Amniotic Fluid Changes • Amniotic fluid peak 38wks ---- 1000ml 40wks ---- 800ml 42wks ---- 480ml 43wks ---- 250ml 44wks ---- 160ml • After 42wks there is 33% decrease in amniotic fluid volume/wk • A decrease in fetal renal blood flow is associated with postdatism is the cause of oligohydromnios • Amniotic fluid less than 400ml is associated with fetal complications

7. Method to evaluate amniotic fluid volume • Most popular method to evaluate amniotic fluid volume is four quadrant technique to calculate Amniotic Fluid Index (AFI). • AFI is obtained by measuring the vertical diameter of largest pocket of amniotic fluid in 4 quadrants of uterus by USG and the sum of the result is AFI • AFI <5cm – oligohydromnios 5 – 10cm – decreased amniotic fluid volume 10 – 15cm – Normal 16 – 20cm – Increased amniotic fluid volume >25cm - Polyhydromnios

8. Qualitative Changes in Amniotic fluid • AF become milky and cloudy because of presence of abundant flakes of vernix caseosa. • The Phospholipids composition changes due to presence of large number of lamellar bodies released from fetal lungs. Vernix raises the lecithin, Sphingomyelin ratio to 4: 1 & more • The liquor may be meconium stained as a result of intrauterine hypoxia

9. Placental Changes • USG findings: -Indentation in chorionic plate become more marked, giving the appearance of cotyledons - Increased confluency of the comma- like densities that become the inter cotyledonary septations - Appearance of hemorrhagic infarct & Calcification

10. Fetal Changes • The fetus grow in utero after term - macrosomic which lead to fetopelvic disproportion , Prolong labor Shoulder dystosia • After term the fetus loses Vernix caseosa causing wrinkling of the skin due to direct contact with aqueous amniotic fluid • Growth of hair and nails • Wasting of subcutaneous tissue

11. Diagnosis of Postdated Pregnancy • The diagnostic accuracy of post term pregnancy hinges on the reliability of gestational age • We can get accurate EDD by:- - LMP when >3 normal regular period before LMP & no ocp - EDD calculated by LMP coincide with EDD from USG perform between 12-20wks - When LMP not known EDD established from USG between 7-11wks - EDD corresponds to 36wks since the patient had +ve upt - A reliable P/V finding for GA age in 1st trimester

12. Management • Prior to deciding any line of action it is important to establish the diagnosis of post term gestation by history , examination and USG. • Fetal Surveillance by – NST - AFI - Biophysical Profile - Doppler ( Facilities available)

13. Patient with Prolonged Pregnancy (>40wks) who need to be delivered : * Women with medical or obstetrical complications of pregnancy * Favorable Cervix Bishop Score > 8 * Women with oligohydromnios * Estimated fetal weight > 4.5kg * Suspected fetal compromise * Fetal congenital anomaly * Hyper mature Placenta

14. Expectant management of prolonged pregnancy is justified only when: - GA <41 wks with unripe cervix, normal AFI , normal size baby , normal BPP and reactive NST • There is universal agreement that once pregnancy reaches 42wks delivery mandatory – Induction/ CS -If there is signs of fetal distress ,wt. is > 4.5kg.or obstetrical complicated pregnancy- CS

15. Complication of Postdated pregnancy Maternal – Increased morbidity due to increased Instrumental & operative delivery Fetal - Intrapartum fetal distress - MAS - Fetal trauma due to macrosomia - Increased Perinatal morbidity & mortality

16. INDUCTION OF LABOUR

17. Induction Initiation or stimulation of uterine contractions before the spontaneous onset of labour with or without ruptured membranes • Augmentation– refers to stimulation of uterine contractions that are already present but found to be inadequate.

18. Indications Obstetrical indication • Post term pregnancy • Severe pre eclampsia/ eclampsia • PROM • Ruptured membrane with chorioamniotis • Intrauterine death • Fetal growth restriction • Nonreassuring fetal testing

19. Rh iso-immunization • Malformed fetus • Abruptio Planctae • Severe hydramnios Medical indication • Chronic nephritis/ renal disease • Chronic Hypertension • Diabetes

20. Contraindication • Fetal macrosomia • Multifetal gestation • Malpresentation • Prior classical caesarean • Contracted pelvis • Major degree placenta previa • Active genital herpes infection • Cervical cancer

21. PREREQUISITES Prior to initiation of induction the following should be assessed • indication for induction/any contraindications • gestational age • cervical favourability (Bishop score assessment) • assessment of pelvis and fetal size/presentation • membrane status (intact or ruptured) • fetal well being/fetal heart rate monitoring prior to labour Induction • documentation of discussion with the patient including indication for induction and disclosure of risk factors

22. CERVICAL RIPENING PRIOR TO INDUCTION • Cervical ripening is a component of induction of labor employed when the cervix is unfavorable in order to facilitate dilatation when labor is established.

23. Bishop’s Score (Modified)

24. Total Score – 13 • Unfavorable Score – 0-5 • Favorable Score - 6-13 • Bishop score >8 is a good index of inducibility

25. Methods of cervical ripening Pharmacological methods • Oxytocin • Prostaglandins -E2(dinoprostone,prepidil,cervidil) -E1(misoprost) • Steroid receptor antagonists -Mifepristone (RU486) -Onapristone • Relaxin

26. Mechanical methods • Membrane stripping • Amniotomy • Mechanical dilators • Transcervical balloon catheters • With extraamniotic saline infusion • With concomitant oxytocin administration

27. Methods of Induction of labor • Medical – Prostaglandins (PGE2, PGE1) - Oxytocin - Mifepristone • Surgical - Artificial rupture of membranes - Stripping the membranes • Combined - Medical + Surgical

28. Prostaglandin E2 • Gel preparation with 0.5mg in 2.5ml in a prefilled syringe for intracervical administration (prepidil/ dinoprostone • With the woman in dorsal the tip of a prefilled syringe is placed intracervically and the gel is deposited just below the internal cervical os.The woman should remain reclined for at least 30 minutes. • Dose repeated every 6 hours with a maximum of 3 doses • Subsequent augmentation with oxytocin if needed to be started after 6 hours • Side effects- uterine tachysystole • Contraindication- asthma, glaucoma , liver disease

29. Prostaglandin E1 • Used as 25µg per vaginally every 4 hours or 50µg per orally every 3-6 hours • Sublingual and buccal routes associated with rapid onset action and more bioavalibility • Maximum dose of 200µg given • Synto augmentation if required to be started after 6 hours • Side effects- uterine tachysystole, fetal distress, uterine rupture • Contraindicated in patients with previous uterine scar, liver disease and renal disease

30. Oxytocin • Polypeptide hormone produced in hypothalamus, secreted from posterior pituitary • Synthetic analogue of used as uterotonic and for induction • Myometrial sensitivity increases with gestational age, with rapid increase during labour • Effective means of induction in women with ripe cervix • Because of short half life (3-4min) used as iv infusion. Plasma levels falls rapidly when iv infusion stopped. • Oxytocin infusion is commenced at the rate of 1-2miu/min and gradually dose increment at 15-30min

31. 2.5 IU Oxytocin in 500ml RL(concentration- 5mIU/ml) 8 drops- 2.5mIU/ml 16 drops- 5mIU/ml 24 drops- 7.5mIU/ml 32 drops- 10 mIU/ml 40 drops- 12.5mIU/ml 48 drops- 15 mIU/ml 56 drops- 17.5 mIU/ml 60 drops- 20 mIU/ml

32. Complications • Uterine overactivity • Water intoxication • Hypotension • Uterine rupture • Neonatal jaundice

33. Mifepristone • Progestrone receptor antagonist • Blocks both progestrone and glucocorticoid receptors • 200mg vaginally daily for 2days has been found to ripen the cervix and to induce labour

34. Membrane stripping • Digital separation of chorioamniotic membrane from wall of cervix and lower uterine segment • Results in local release of endogenous prostaglandins • Vertex should be well applied to cervix and os should be dilated to allow examining finger • Complications- membrane rupture, haemorrhage from disruption of occult placenta praevia, chorioamnionitis

35. Transcervical Foley’s catheter • placed through cervical os inflated with 30-50cc saline • Downward tension that is created by taping the catheter to the thigh can lead to cervical ripening • The catheter is left in place until it spontaneously falls out or upto 24 hours • Intracervical foley’s catheter can be combined with oxytocin or vaginal misoprostol or they can be started 12-24 hours after insertion. • Preferred in woman where prostaglandins are contraindicated. • Cotraindication-low lying placenta,APH, rupture of membrane, cervicitis

36. Factors that increase success of labour induction • Favourable cervix • Multiparity • Bodymass index<30 • Birthweight<3500gm