Table 1 Trial eligibility - maternal exclusion criteria

• ≥ 40 years of age and ≤16 years age at delivery

• Grand multiparity (> 5)

• Height: < 152 cms (5 feet)

• BMI < 18 or > 29

• Medical History: respiratory, renal, infective, immune, neurological, cardiovascular, gastrointestinal, endocrine, haematological, mental ill-health, muscoskeletal

• Social

Current history of drug misuse

Smoking ≥ 20 cigarettes per day

• Latex allergy

• Previous obstetric history

History of preterm birth at < 34 weeks gestation, recurrent miscarriage, moderate to severe pre-eclampsia,intra-uterine growth restriction, previous stillbirth, CS, eclampsia, uterine rupture, placental abruption, PUPP, obstetric cholestasis, 3rd or 4th degree tear, PPH (> 500 mls or symptomatic), manual removal of placenta, shoulder dystocia, midtrimester miscarriage, neonatal death, infant with hypoxic ischaemic encephalopathy

• Previous gynaecological history

Uterine surgery, myomectomy, hysterotomy, cone biopsy (unless subsequent term vaginal delivery), two previous Letz procedures, uterine fibroids, cervical cerclage, infertitlity, uterine anomaly, perineal reconstruction (more than 24 hours post birth)