Urinary stress incontinence is more likely following vaginal than caesarean section (CS) delivery of twins, a multinational randomised controlled trial has shown.

A total of 2,804 women were recruited to the Twin Birth Study between 32 weeks and term. All the women had uncomplicated twin pregnancies where the presenting fetus was cephalic.

Around half were randomised to planned CS delivery the other half to planned vaginal delivery. The groups were comparable in terms of maternal age, parity, previous CS, and history of previous incontinence.

Overall, 2,305 women (82.2%) were followed up after two years, of whom 1,155 were randomised to planned CS and 1,150 to planned vaginal delivery. Data were analysed on an intention to treat basis.

In the planned CS group, 1,035 (89.6%) delivered both twins by CS (of which 609 CS were performed prior to the onset of labour); 113 (9.8%) had a vaginal delivery of both babies, and seven (0.6%) had a vaginal delivery of one of the twins.

In the planned vaginal delivery group, 700 (60.8%) delivered both (657) or one (43) of the babies vaginally. A total of 450 (39.1%) had both twins delivered by CS.

Two years after delivery women were questioned about whether they had urinary, faecal, or flatal incontinence. Those who were classified as having problematic incontinence were asked to complete an Incontinence Impact Questionnaire (IIQ-7). The possible scores ranged from 0 (no impact) to 100 (great impact).

Urinary incontinence was more common in women assigned to vaginal delivery. The figures for problematic incontinence were 93 (8.1%) and 140 (12.2%) for the planned CS and vaginal delivery groups respectively; adjusted odds ratio (AOR) 0.63 (95% CI: 0.47-0.83, P = 0.001). The impact of incontinence measured by the IIQ-7 questionnaire was similar in the groups with mean IIQ-7 scores of 18.4 and 19.1 respectively (P = 0.82).

In those women with no prior history of incontinence the rates were 6.8% for planned CS and 11.6% for planned vaginal birth, respectively AOR 0.56 (95% CI: 0.41-0.76, P = 0.0002). In those women who had a prior history of urinary incontinence no significant difference between the groups was observed (30.8% for planned CS and 24.1% for planned vaginal birth; AOR 1.4 (95% CI: 0.60-3.24, P = 0.44).

There were no differences in problematic faecal or flatal incontinence rates, or any other maternal outcomes, between the groups.

Maternal stress urinary incontinence is more common in the first few months after vaginal delivery following breech presentation than after CS in singleton pregnancies.¹ However, in the longer term, this difference disappears. The present large study has shown that this is not the case following twin pregnancy delivery.

Although an earlier study by the same investigators had found no significant early differences in neonatal outcome for planned CS versus planned vaginal birth in uncomplicated twin delivery² this later study has shown that urinary incontinence was significantly lower in women allocated to a planned CS compared with planned vaginal birth, but only in women with no previous history of incontinence.

Ultimately, the decision whether to opt for an elective CS or a planned vaginal birth will need to be made by the woman in concert with her obstetrician.

The study authors conclude: ‘We found that planned caesarean delivery reduced the risk of problematic urinary stress incontinence, compared with planned vaginal birth, at 2 years postpartum for the mothers of twins with no prior history of problematic urinary stress incontinence. Although this information may not, in itself, form the basis for a decision in favour of caesarean birth, it should be included in the counselling of women with twin pregnancies so that they can make an informed decision as to their preferred method of birth.’

Dr Chris Barclay