Methods
Participants
The sample comprised nulliparous women expected to deliver
at ‡37 weeks of gestation with live singleton cephalic pregnancies
and no contraindication to vaginal birth. We
excluded women who were less than 16 years or with limited
ability to speak or understand English.
Recruitment setting and procedures
The maternity unit in Scotland recruited women from October
2004 to September 2006, and the unit in South West
England recruited women from June 2005 to August 2006.
The annual rates of OVD were 14.5 and 11%, respectively,
which are representative of UK national rates. The Scottish
unit had a preference for forceps delivery (80% of OVD) and
the English unit similar rates of forceps (51%) and vacuum
delivery (49%). Women were recruited in the third trimester,
either when attending for antenatal care or when admitted for
induction of labour. We did not receive ethics approval to
recruit women in labour. After discussing the trial, women
expressing an interest in participation were given an information
sheet, a written consent form and a baseline questionnaire
on pelvic floor symptoms. On completion of the forms,
women were included in the study. Consent to participation
in the trial was reconfirmed verbally immediately prior to
randomisation in the second stage of labour.
Randomisation
Stickers in the woman’s maternity records alerted health professionals
to her participation in the study. Women were
randomised to one of two groups if they required an OVD
in the second stage of labour. The randomisation was performed
by computer program using a randomisation
sequence generated by a statistician unconnected with the
study. Allocation was stratified by maternity unit using randomly
permuted blocks of 10. Due to the need to randomise
women 24 hours a day, the patient’s hospital number was
entered into the program by the obstetrician or midwife caring
for the woman in labour, and the allocation was revealed
immediately prior to commencing the OVD. Some randomisations
were allocated using opaque envelopes due to technical
difficulties with the programme. Adherence to the
allocation was confirmed by the research midwife each day.
Interventions
Womenwere allocated to routine use of episiotomy (in all cases)
or restrictive use of episiotomy (only if tearing becomes apparent).
Women received usual care for all other aspects of the birth.
Clinical characteristics
Body mass index (BMI) was measured as booking weight/
height (kg/m2). Small for gestational age was defined as
a birthweight less than the 10th percentile using individualised
birth rate ratios (corrected for maternal height and
weight, parity, infant sex, ethnicity and gestation) (www.
gestation.net). Total duration of labour included both the
first and the second stages of labour and was recorded as
a continuous variable. Labour was classified as prolonged if
it exceeded 12 hours (average duration for nulliparous), and
the dichotomous variable was included in multiple regression
analyses. The second stage of labour included the passive and
active phases and was considered prolonged if more than 2
hours duration, although it is recognised that a longer second
stage may be appropriate, particularly with epidural analgesia.
A cardiotocograph showing persistent late decelerations,
tachycardia (>160 beats per minute) with decelerations or
bradycardia for more than 10 minutes in the second stage
of labour was considered pathological.8 Fetal malposition
was defined as either occipitotransverse or occipitoposterior
position.
Outcome measures
The primary outcome measure was extensive perineal tearing
involving the anal sphincter (third- or fourth-degree tears).
Each woman had a systematic vaginal and rectal examination
following delivery. Classification of anal sphincter tears was
according to the Royal College of Obstetricians & Gynaecologists
(RCOG) green-top guideline.9 Secondary outcomes
investigated were postpartum haemorrhage (PPH), shoulder
dystocia, the mother’s perception of pain, the length of postnatal
hospital stay, urinary or bowel symptoms and the rate of
healing complications. Neonatal outcomes included low
Apgar scores, low arterial blood gases, admission to the neonatal
intensive care unit and trauma. Estimated blood loss was
a global estimate as routine weighing of swabs and other
methods of formal blood loss assessment were not performed.
Primary PPH was defined as an estimated blood loss at delivery
and in the first 24 hours of more than 500 ml. Use of a
urinary catheter beyond 24 hours was regarded as prolonged.
Moderate or strong analgesia was defined as any analgesia excluding
paracetamol (usually nonsteroidal anti-inflammatory