Postdated Pregnancy Induction Of Labor Postterm Pregnancy Syn

Post-dated Pregnancy & Induction Of Labor

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%

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%

• Abnormal fetal HPA and adrenal hypoplasia as in anencephaly deficiency of dehydroepiandrosterone 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

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

Quantitative Amniotic Fluid Changes • Amniotic fluid peak 38 wks ---- 1000 ml 40 wks ---- 800 ml 42 wks ---- 480 ml 43 wks ---- 250 ml 44 wks ---- 160 ml • After 42 wks 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 400 ml is associated with fetal complications

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 <5 cm – oligohydromnios 5 – 10 cm – decreased amniotic fluid volume 10 – 15 cm – Normal 16 – 20 cm – Increased amniotic fluid volume >25 cm - Polyhydromnios

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

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

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

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 -20 wks - When LMP not known EDD established from USG between 7 -11 wks - EDD corresponds to 36 wks since the patient had +ve upt - A reliable P/V finding for GA age in 1 st trimester

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)

• Patient with Prolonged Pregnancy (>40 wks) 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. 5 kg * Suspected fetal compromise * Fetal congenital anomaly * Hyper mature Placenta

• 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 42 wks delivery mandatory – Induction/ CS -If there is signs of fetal distress , wt. is > 4. 5 kg. or obstetrical complicated pregnancy- CS

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

INDUCTION OF LABOUR

• 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.

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

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

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

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

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.

Bishop’s Score (Modified) Parameters Cervix Score 0 1 2 3 Dilatation (Cm) Closed 1 -2 3 -4 Effacement(%) Or Cervical Length (Cm) 0 -30 Or >4 40 -50 or 2 -4 60 -70 or 1 -2 ≥ 80 or <1 Consistency Firm Medium Soft - Position Posterior Midline Anterior - -2 - 1, 0 Head Station -3 5+ +1, +2

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

Methods of cervical ripening Pharmacological methods • Oxytocin • Prostaglandins -E 2(dinoprostone, prepidil, cervidil) -E 1(misoprost) • Steroid receptor antagonists -Mifepristone (RU 486) -Onapristone • Relaxin

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

Methods of Induction of labor • Medical – Prostaglandins (PGE 2, PGE 1) - Oxytocin - Mifepristone • Surgical - Artificial rupture of membranes - Stripping the membranes • Combined - Medical + Surgical

Prostaglandin E 2 • Gel preparation with 0. 5 mg in 2. 5 ml 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

Prostaglandin E 1 • 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

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 -4 min) used as iv infusion. Plasma levels falls rapidly when iv infusion stopped. • Oxytocin infusion is commenced at the rate of 1 -2 miu/min and gradually dose increment at 15 -30 min

2. 5 IU Oxytocin in 500 ml RL(concentration- 5 m. IU/ml) 8 drops- 2. 5 m. IU/ml 16 drops- 5 m. IU/ml 24 drops- 7. 5 m. IU/ml 32 drops- 10 m. IU/ml 40 drops- 12. 5 m. IU/ml 48 drops- 15 m. IU/ml 56 drops- 17. 5 m. IU/ml 60 drops- 20 m. IU/ml

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

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

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

Transcervical Foley’s catheter • placed through cervical os inflated with 30 -50 cc 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 1224 hours after insertion. • Preferred in woman where prostaglandins are contraindicated. • Cotraindication-low lying placenta, APH, rupture of membrane, cervicitis

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