4.1Prolonged pregnancy

Bibliographic detailsStudy type and evidence levelNumber of patientsPatient characteristicsIntervention and comparisonFollow-up and outcome measures effect sizeReviewer comments
Hilder (1998)21

Country: UK
Study Type: Observational retrospective analysis

Evidence Level: 3
171 527 birthsNotified births in NE Thames Region, London 1989 – 1991Stillbirth and infant mortality rates at term and post-term gestation.Stillbirth/1000 ongoing pregnancies

37 weeks GA
0.35 (95% CI 0.26 to 0.44)
38 weeks GA
0.56 (95% CI 0.44 to 0.68)
39 weeks GA
0.57 (95% CI 0.44 to 0.70)
40 weeks GA
0.86 (95% CI 0.68 to 1.05)
41 weeks GA
1.27(95% CI 0.92 to 1.62)
42 weeks GA
1.55 (95% CI 0.79 to 2.31)
≥ 43 weeks GA
2.12 (95% CI 0.55 to 5.43)

Neonatal and post neonatal mortality/1000ongoing pregnancies

37 weeks GA
0.34 (95% CI 0.25 to 0.43)
38 weeks GA
0.70 (95% CI 0.56 to 0.83)
39 weeks GA
0.83 (95% CI 0.68 to 0.99)
40 weeks GA
1.57 (95% CI 1.31 to 1.82)
41 weeks GA
1.48 (95% CI 1.10 to 1.85)
42 weeks GA
3.29 (95% CI 2.19 to 4.40)
≥ 43 weeks GA
3.71 (95% CI 1.53 to 7.63)

Total pregnancy loss rate/1000 ongoing pregnancies

37 weeks GA: 0.7
38 weeks GA: 1.3
39 weeks GA: 1.4
40 weeks GA: 2.4
41 weeks GA: 2.8
42 weeks GA; 4.8
≥ 43 weeks GA: 5.8
Induced labours included, number unknown
Olesen (2003)27

Country: Denmark
Study Type: Cross-sectional

Evidence Level: 3
Post-term delivery (n = 77 956)

Gestational age:
42 weeks (87.5%)
43 weeks (11.6%)
44 weeks (0.8%)
45+ weeks (0.1%)

Induced delivery after 42 weeks: 24.5%

Term delivery
(n = 34 140)
Gestational age:
37–39 weeks (34.5%)
40–41 weeks (65.5%)
Registry data 1978–1993

All singleton deliveries
Post-term delivery versus term deliveryPerinatal outcomes

Aspiration: 1.3% versus 0.7%, Adjusted OR 1.75 (95% CI 1.52 to 2.02)
Asphyxia before delivery: 0.8% versus 0.4%, Adjusted OR 1.90 (95% CI 1.58 to 2.30)
Asphyxia during delivery: 0.2% versus 0.1%, Adjusted OR 2.00 (95% CI 1.33 to 3.01)
Asphyxia in perinatal period: 1.5% versus 0.9%, Adjusted OR 1.63 (95% CI 1.43 to 1.85)
Asphyxia in neonatal period: 2.4% versus 1.6%, Adjusted OR 1.33 (95% CI 1.62 to 1.85)
Apgar score at 5 minutes < 7: 0.95 versus 0.6%, Adjusted OR 1.44 (95% CI 1.23 to 1.69)
Pneumonia: 0.2% versus 0.2%, Adjusted OR 1.47 (95% CI 1.07 to 2.01)
Septicaemia: 0.5% versus 0.4%, Adjusted OR 1.37 (95% CI 1.12 to 1.67)
Stillbirth: 0.2% versus 0.2%, Adjusted OR 1.24 (95% CI 0.93 to 1.66)
Death day 1–7: 0.1% versus 0.1%, Adjusted OR 1.60 (95% CI 1.07 to 2.37)
Perinatal death: 0.4% versus versus 0.3%, Adjusted OR 1.36 (95% CI 1.08 to 1.72)

Maternal complications
Puerperal infection: 0.8% versus 0.7%, Adjusted OR 1.21 (95% CI 1.03 to 1.41)
Post-partum haem: 5.0% versus 3.6%, Adjusted OR 1.37 (95% CI 1.28 to 1.46)
Large fetus: 0.6% versus 0.2%, Adjusted OR 3.58 (95% CI 2.72 to 4.70)
Cephalopelvic disproportion: 4.6% versus 2.4%, Adjusted OR 1.91 (95% CI 1.77 to 2.07)
Vulval incomplete rupture: 5.5% versus 5.8%, Adjusted OR 0.96 (95% CI 0.91 to 1.02)
Vulval complete rupture: 0.7% versus 0.6%, Adjusted OR 1.11 (95% CI 0.95 to 1.30)
Cervical rupture: 1.1% 0.7%, Adjusted OR 1.45 (95% CI 1.26 to 1.67)
Delivery with threatening asphyxia: 8.0% versus 3.9%, Adjusted OR 2.03 (95% CI 1.91 to 2.16)
Dystocia: 0.3% versus 0.2%, Adjusted OR 1.71 (95% CI 1.30 to 2.25)
Acute CS: 12.8% versus 8.2%, Adjusted OR 1.58 (95% CI 1.51 to 1.66)
Not clear if women were low-risk

Induced labours excluded

Post-term pregnancy:
≥ 42 weeks
Smith (2001)26

Country: Scotland
Study Type: Case-series

Evidence Level=3
Birth data
(n = 700 878)
National database in Scotland 1985–1996

All deliveries singletons
Perinatal death at term and postterm.Cumulative probability of antepartum stillbirth (per 1000 ongoing pregnancy)
At 37 weeks: 0.4
At 38 weeks: 0.8
At 39 weeks: 1.3
At 40 weeks: 2.2
At 41 weeks: 3.4
At 42 weeks: 5.3
At 43 weeks: 11.5

Probability of intrapartum stillbirth (per 1000 live birth):
At 37 weeks: 0.7
At 38 weeks: 0.3
At 39 weeks: 0.2
At 40 weeks: 0/3
At 41 weeks: 0.3
At 42 weeks: 0.4
At 43 weeks: 0
Excluded: multiple pregnancies and deaths caused by congenital abnormalities

Induced labours included, number unknown
Funding: Wellcome Trust
Heimstad (2006)28

Country: Norway
Study type: Prospective study

Evidence level = 3
Pregnancies
(n = 27 514, labour induced in 2500)

Para 0: 43%
Para 1: 38%
Para 2: 20%
Gestations beyond 37 weeks, all singleton deliveries.Pregnancy outcomes by weeks of gestationMaternal complications:
Induced versus spontaneous labour

Caesarean delivery
At 37 weeks: OR 1.2 (95% CI 0.8 to 1.8)
At 38 weeks: OR 2.5 (95% CI 1.8 to 3.4)
At 39 weeks: OR 3.8 (95% CI 2.7 to 5.2)
At 40 weeks: OR 3.8 (95% CI 2.8 to 5.0)
At 41 weeks: OR 4.0 (95% CI 3.0 to 5.4)
At 42 weeks: OR 2.8 (95% CI 2.2 to 3.7)

Operational vaginal delivery
At 37 weeks: OR 2.0 (95% CI 1.2 to 3.2)
At 38 weeks: OR 2.2 (95% CI 1.5 to 3.0)
At 39 weeks: OR 1.7 (95% CI 1.2 to 2.3)
At 40 weeks: OR 1.6 (95% CI 1.2 to 2.1)
At 41 weeks: OR 2.0 (95% CI 1.6 to 2.7)
At 42 weeks: OR 1.0 (95% CI 0.8 to 1.3)

Maternal haemorrhage
At 37 weeks: OR 1.9 (95% CI 1.2 to 2.9)
At 38 weeks: OR 1.8 (95% CI 1.3 to 2.7)
At 39 weeks: OR 1.9 (95% CI 1.3 to 2.7)
At 40 weeks: OR 2.2 (95% CI 1.7 to 2.8)
At 41 weeks: OR 2.3 (95% CI 1.7 to 3.1)
At 42 weeks: OR 1.5 (95% CI 1.1 to 2.0)

Fetal complications
Meconium aspiration (per 1000 births)
At 37 weeks: 2.5
At 38 weeks: 2.3
At 39 weeks: 1.8
At 40 weeks: 2.9
At 41 weeks: 5.1
At 42 weeks: 4.7

Intrauterine fetal death (per 1000 ongoing pregnancies)
At 37 weeks: 0.35
At 38 weeks: 0.25
At 39 weeks: 0.43
At 40 weeks: 0.51
At 41 weeks: 0.84
At 42 weeks: 1.55

Risk factors for delivery complications by logistic regression analysis:
Induction of labour: OR 1.3 to 2.8, independent of gestational age
Not clear if women were low-risk

Induced labours: 9%

Funding: not stated
Caughey (2006)29

Country: US
Study type: Retrospective cohort

Evidence level: 3
Pregnant women (n = 32 828)

Nulliparous: 52.1%

Labour induced: 12.2%

Birthweight ≥ 4000 g: 12.6%
Sugmentation of labour: 25.7%

Caesarean delivery: 17.6%

Primary caesarean rate: 11.7%

Operative vaginal delivery: 15%
Low-risk women 37 to 40 weeks of gestation, all singleton deliveries.Mode of delivery.

Maternal complications by weeks of gestation.
Mode of delivery

Primary caesarean (%)
At 37 weeks: 9.7
At 38 weeks: 8.7
At 39 weeks: 9.2
At 40 weeks: 10.4**
At 41 weeks: 14.1**
At 42 weeks: 18.1***

Operative vaginal delivery (%)
At 37 weeks: 14.9
At 38 weeks: 14.0
At 39 weeks: 14.8*
At 40 weeks: 16.4**
At 41 weeks: 17.4**
At 42 weeks: 20.2***

Mode of delivery
Primary caesarean (%)
At 37 weeks: 10.9
At 38 weeks: 10.2
At 39 weeks: 11.4
At 40 weeks: 14.2**
At 41 weeks: 18.9***
At 42 weeks: 25.9***

Operative vaginal delivery (%)
At 37 weeks: 22.0
At 38 weeks: 20.7
At 39 weeks: 21.9
At 40 weeks: 23.1*
At 41 weeks: 23.0
At 42 weeks: 26.4***

Maternal complications by weeks of gestation Postpartum haem
At 37 weeks: 14.2
At 38 weeks: 12.6
At 39 weeks: 13.4
At 40 weeks: 12.8
At 41 weeks: 16.0***
At 42 weeks: 15.8

*< 0.05, ** < 0.01. *** < 0.001
(Statistical significant as compared with the rate in the prior week of gestation)
Funding: NICHHD

Induced labours:12%
Gulmezoglu (2006)31

Country: France, Norway, Turkey, India, Thailand, China, UK, US, Canada
Study type: systematic review

Evidence level: 1++
19 RCTs (7984 women)Trials conducted between 1969 to 2005

Participants were low-risk women with certain gestational age

Induction at 38–40 weeks (3 trials)

Induction at 41 completed weeks (11 trials)

Induction after 42 completed weeks (5 trials)
Planned induction of labour (All methods, singly or in combination: membrane sweeping, AROM, laminaria tents, prostaglandins, misoprostal, oxytocin)

versus

No induction (Expectant management: monitoring with fetal movements, nonstress tests, amniotic fluid measurement and ultrasound etc).
Perinatal death
Induction at 41 completed weeks (10 RCTs): (0/2835 versus 6/2808, RR 0.25 (95% CI 0.05 to 1.18)
Induction at 41 and 42 completed weeks (12 RCTs): RR 0.30 (95% CI 0.09 to 0.99)
Excluding death due to congenital anomalies: 0 versus 9

Birth asphyxia
Induction at 38–40 weeks (1RCT): (29/481 versus 7/235; RR 2.02 (95% CI 0.90 to 4.55)
Induction at 41 completed weeks (1RCT): (1/124 versus 0/125)

Meconium aspiration syndrome
Induction at 41 completed weeks (4 RCTs): RR 0.29 (95% CI 0.12 to 0.68)
Induction after 42 completed weeks (2 RCTs): RR 0.66 (95% CI 0.24 to 1.81)

Mean birthweight (g):
Induction at 41 completed weeks
Similar between groups
Induction after 42 completed weeks (3 RCTs):
WMD ─101.67 (95% CI ─179.12 to ─24.23)

Caesarean section
Induction at 38–40 weeks: RR 0.58 (95% CI 0.34 to 0.99)
Induction at 41 completed weeks: RR 0.92 (95% CI 0.76 to 1.12)
Induction after 42 completed weeks: RR 0.97 (95% CI 0.72 to 1.31)

Assisted vaginal birth
Induction at 38–40 weeks: RR 1.71 (95% CI 1.23 to 2.39)
Induction at 41 completed weeks: RR 1.05 (95% CI 0.94 to 1.17)
Induction after 42 completed weeks: RR 0.95 (95% CI 0.65 to 1.38)

Cervical status (8 trials):
No significant difference between induction and expectant management for CS or assisted vaginal birth

Maternal anxiety/satisfaction:
Not reported in any of the trials
Gestational age not confirmed by ultrasound in some trials.

9 trials conducted after 1990

4 trials conducted in developing countries

Funding: WHO, University of Adelaide
Hannah (1992)33

Country: Canada
Study type: Randomised Controlled Trial

Evidence level: 1+
Total number of patients = 3407

Induction of labour with intracervical PGE2 gel n = 1701

Serial monitoring n = 1706
Uncomplicated pregnancies ≥ 41 weeks GA

Nulliparity
Induction: 68%
monitoring: 68%

Cervical dilation before entry 0 cm
Induction: 40%
monitoring: 40%

1–2 cm
Induction: 51%
monitoring: 49%

3–4 cm
Induction: 1%
monitoring: 1%
Induction of labour (PGE2 gel) versus Serial monitoringCaesarean section rate: 21.2% versus 24.5% (P = 0.003)

instrumental vaginal birth rate: 35.3% versus 34.9% (NS)

intrapartum fever > 38 °C: 2.9% versus 3.6% (NS)

Apgar score < 7 at 5 minutes: 1.1% versus 1.2% (NS)

Seizures: 0.2% versus 0.3% (NS)

Admission to NICU: 14.1% versus 15.5% (NS)

Stillbirth: 0 versus 2

Neonatal death; 0 versus 0
Source of Funding: MRC, Canada

Central randomisation.
Unclear method of allocation concealment
Power calculation

Serial monitoring: underwent non-stress tests 3 times/week, ultrasound assessment of amniotic fluid volume 2–3 times/week

Women asked to count no. of times they felt fetus kick over a 2 hour period each day (kick counts), and to contact their physicians if they counted < 6 kicks in 2 hours and to have a non-stress test within 12 hours

7 women whose infants had major congenital anomalies were excluded from the analysis of perinatal and neonatal outcomes
McNellis (1994)32

Country: USA
Study type: Randomised controlled trial

Evidence level: 1+
Total number of patients = 265

Intracervical PGE2 gel n = 174

Placebo n = 91
Uncomplicated pregnancies 41–43 weeks GA (verified by US)

Nulliparity
PGE2: 60%
Placebo: 59%

Mean Bishop score
PGE2: 4 (SD 1.4)
Placebo: 3.8 (SD 1.4)
Induction of albour (Intracervical PGE2 gel) versus
No induction (placebo)
Randomisation-to-delivery interval (hours): 36 (6–492) versus 35 (7–387) (NS)
Maternal infection: 19% versus 14% (NS)
Maternal need for transfusion: 1% versus 0% (NS)
Uterine hyperactivity: 1% versus 1% (NS)
Vaginal delivery: 77% versus 82% (NS)
CS: 22% versus 18% (NS)
Apgar score < 4 at 5 minutes (No): 0 versus 0 (NS)
No meconium (No.): 131 (75%) versus 71 (78%) (NS)
Thin meconium (No.): 31 (18%) versus 12 (13%) (NS)
Thick meconium (No.): 10 (6%) versus 7 (8%) (NS)
Meconium aspirated pneumonia (No.): 1 versus 1 (NS)
Source of Funding: NICHHD, US

Part of a RCT to assess effects of induction of labour versus expectant management.
Women in the induction group underwent induction within 24 hours of randomisation to PGE2 gel or placebo prior to induction with oxytocin
Power calculation

Computer randomisation in a 2:1 scheme
(PGE2:placebo)
Balchin (2007)30

Country: UK
Prospective cohort study of maternity records

Evidence level: 2+
Total number of women = 197 061 in 15 matenity units81% white, 13% South Asian, 6% black women who delivered a single baby weighing ≥ 500 g at 24–43 weeksCompare perinatal mortality (PNM) according to length of gestation in white, south Asian and black womenCrude PNM rates/1000births
White women vs South Asian women: 5.6 vs 9.2 (OR 1.6, 95% CI 1.4 to 1.9)
White women vs black women: 5.6 vs 10.8 (OR 2.0, 95% CI 1.6 to 2.3)

Crude stillbirth rates/1000births
White women vs South Asian women: 4.3 vs 7.5 (OR 1.8, 95% CI 1.5 to 2.1)
White women vs black women: 4.3 vs 7.8 (OR 1.8, 95% CI 1.5 to 2.3)

Crude antepartum stillbirth rates/1000births
White women vs South Asian women: 3.3 vs 6.2 (OR 1.9, 95% CI 1.6 to 2.2)
White women vs black women: 3.3 vs 6.3 (OR 1.9, 95% CI 1.5 to 2.4)

Crude intrapartum stillbirth rates/1000births
White women vs South Asian women: 0.6 vs 0.5 (OR 0.9, 95% CI 0.5 to 1.5)
White women vs black women: 0.6 vs 1.2 (OR 2.0, 95% CI 1.1 to 3.4)

Crude early neonatal death rates/1000births
White women vs South Asian women: 1.3 vs 1.8 (OR 1.3, 95% CI 1.0 to 1.8)
White women vs black women: 1.3 vs 3.1 (OR 2.3, 95% CI 1.6 to 3.3)

Independent factors associated with antepartum stillbirth (corrected for confounding variables [placental abruption, congenital abnormality, low birthweight, birthweight < 10th centile, meconium opassage, fever, maternal BMI ≥ 30, maternal age ≥ 30])

South Asian: OR 1.8, 95% CI 1.2 to 2.7
none

From: Evidence tables

Cover of Induction of Labour
Induction of Labour.
NICE Clinical Guidelines, No. 70.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2008 Jul.
Copyright © 2008, National Collaborating Centre for Women's and Children's Health.

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