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Prolonged pregnancy

Max Brinsmead PhD FRANZCOG August 2012. Prolonged pregnancy. Definition and Incidence. Prolonged pregnancy is defined as that proceeding beyond 42 weeks gestation

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Prolonged pregnancy

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  1. Max Brinsmead PhD FRANZCOG August 2012 Prolonged pregnancy

  2. Definition and Incidence • Prolonged pregnancy is defined as that proceeding beyond 42 weeks gestation • In the absence of any medical intervention, the incidence has been described as between 5% and 10% of women with singleton pregnancies

  3. The Problem • Epidemiological studies demonstrate that perinatal mortality rises beyond 41w • Doubles at 42 weeks and • Triples at 43 weeks but... • This is from a very low baseline so the absolute risk is small • Approx. 3 per thousand but... • There are racial and ethnic differences • Lowest in whites • Higher in blacks • Highest is southern Asians in a UK study

  4. Increased Perinatal Mortality may be due to… • “Ageing” of the placenta • Increasing rates of meconium and meconium aspiration • This occurs with intrauterine asphyxia • Increasing size of the fetus... • Although most studies point to relative IUGR as a risk factor post term • And increased rates of CS after 42w are for fetal distress rather than CPD or failure to progress

  5. Induction of Labour (IOL) • Carries risks such as... • Uterine hyperstimulation from oxytocic agents • Chorioamnionitis from amniotomy • Cord prolapse & fetal bleeding from vasa previa (rare) • The “intervention cascade” • Failed induction of labour • It requires induction of labour in some 470 women to prevent one perinatal death

  6. What is the Evidence? • Metanalysis of 19 RCT’s with 7984 women concludes that IOL at 41 – 42 weeks compared to conservative management results in lower PNM • RR 0.30, CI 0.09 – 0.99 • But there are many problems with all of the trials e.g. • Protocol violations • They are unblinded • May not be relevant for all populations

  7. Perinatal deaths in the control group… • Meconium aspiration (4) • Intrauterine death (2) • But one occurred in a mother with gestational diabetes • Neonatal pneumonia (1) • GBS screening presumably not done • There were no deaths in the IOL group

  8. Safe conservative management is possible • In a RCT of 508 women in Sweden • 254 subject to IOL at 41w & 2d • 254 monitored by CTG and AFI every 3rd day to 43w • There was no difference in: • Rate of Caesarean birth • Rate of assisted vaginal birth • Severe perineal injury or PPH • Meconium liquor • 5-minute Apgar • Admission to NICU • Perinatal death (one only in controls due to true knot in the cord)

  9. From a practical point of view • A policy of routine induction of labour is only applicable if dates are known with accuracy • This requires routine ultrasound to confirm dates at <16 weeks gestation • NICE guidelines • It is best practice to discuss the pros and cons of IOL with women & to involve them in the decision process

  10. When dates are certain then NICE guidelines recommend… • That information about prolonged pregnancy is provided to all women and specifically at 38+w. • At 40 - 41w nulliparous women be offered vaginal examination (VE) with membrane sweeping • At 41w parous women be offered VE with membrane sweeping • That all women with uncomplicated pregnancies be offered induction of labour at 41 – 42w

  11. Membrane Sweeping • A systematic review of 22 RCT’s with 2797 women shows that sweeping the membranes... • Reduces the number of pregnancies >41 w RR 0.59, CI 0.46 – 0.74 • Saves one induction of labour for every 8 performed • Has no effect on the rate of CS • Has no increased risk of maternal or neonatal infection • Causes some pain in most women • Causes uncomplicated bleeding in a few women • Is more successful in parous women than nulliparas

  12. Membrane Sweeping (2) • Unanswered questions include... • When it should be commenced • How often • What can be done if the cervix is closed • Sweeping in the vaginal fornix is recommended

  13. If a patient declines induction of labour past term NICE guidelines recommend… • That patients be offered increased surveillance and nothing less than... • Twice weekly CTG • An ultrasound estimate of amniotic fluid volume • There may be advantages in continuing VE’s and sweeping of membranes

  14. When dates are uncertain then it is appropriate… • That an assessment is made at each visit of the possible risks associated with prolonged pregnancy and the risks associated with induction of labour • This includes the possible risk of delivering a premature infant in error • The assessment may or may not include VE and sweeping of membranes

  15. Concern when monitoring a fetus at risk from prolonged pregnancy MAY include… • Maternal conditions known to be associated with a risk of intrauterine death e.g. • Gestational diabetes • Hypertension in pregnancy • Smoking • Recurrent APH • Malaria and severe anaemia etc. • Past obstetric history of... • Stillbirth or neonatal death • Meconium-complicated pregnancies • IUGR • Oligohydramnios • Decreasing fetal movements • Failure of maternal weight gain • Static symphysis-fundal height

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