Max Brinsmead MB BS PhD May 2015

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

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

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

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

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

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

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 3 rd 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)

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

When dates are certain then NICE guidelines recommend…  That information about prolonged pregnancy is provided to all women and specifically at 38+w.  At w 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

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

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

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

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

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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