Mode of Delivery in Multiple Pregnancy

Amir Aviram, Jon F. R. Barret, Elad Mei-Dan and Nir Melamed

The Facts

Multiple pregnancies carry a higher risk of adverse perinatal outcomes compared with singleton gestations, mainly attributed to preterm delivery and low birthweight.

As such, a twin delivery remains one of the most challenging events in the daily practice of obstetricians. The perennial dilemmas that apply to any singleton delivery, such as intra­partum monitoring and operative interventions, are compounded by the presence of the second fetus. In this chapter we review the evidence concerning mode of delivery in twin gestations and address specific clinical scenarios that are often encountered in daily practice. We also briefly address triplet and higher-order pregnancies, albeit that the evidence base in this regard is limited.

The literature regarding mode of delivery in twins was limited to observational and retrospective cohort studies until the publication of the Twin Birth Study (TBS) in 2013.1 Prior to that only one small-scale randomised controlled trial (RCT) was performed.² This RCT aimed to assess the management of a non-vertex twin B. Sixty women carrying twins (in all of whom twin A was cephalic and twin B was non-cephalic) were randomised to planned vaginal delivery (VD) versus planned CD.

As mentioned previously, all other studies were mainly observational or retrospective in nature. A systematic review and meta-analysis published in 2011 included retrospective observational manuscripts published in the first decade of the millennium. Their results showed that while as a general rule the rate of neonatal morbidity of twin A is lower than that of twin B, it is not associated with mode of delivery or presentation of twin B. They also reported lower rates of neonatal morbidity of twin A in VD as compared with CD.³

In an effort to reconcile different results from different studies, the TBS, a multinational, multicentre, randomised, controlled trial, was initiated in 2003.¹ In the TBS, patients were eligible for recruitment between 32⁺⁰ and 38⁺⁶ weeks of gestation if the first twin was in the cephalic presentation and both fetuses were alive with an estimated weight between 1,500 g and 4,000 g. Exclusion criteria were monoamniotic twins, fetal reduction at 13 or more weeks of gestation, lethal fetal anomaly and contraindication to labour or VD (such as fetal compromise, twin B substantially larger than twin A, two or more previous CDs or vertical uterine incision, etc.). Women were randomised to planned VD or planned CD and delivery was planned between 37+5 and 38+6 weeks of gestation. Mothers and infants were followed up to 28 days after delivery. The primary outcome was a composite of neonatal adverse outcomes, and a composite maternal outcome was also defined.¹ Overall, data were available for a total of 1,392 women in each arm, 2,783 fetuses/infants in the planned CD arm and 2,782 fetuses/infants in the planned VD arm. Approximately 90% of women assigned to the planned CD arm had a CD, 9% had a VD of both twins and 1% had a combined delivery.

No differences in the primary composite neonatal outcome or the composite maternal outcome were found between the groups. These results did not change in the pre-specified subgroup analyses according to parity, gestational age at randomisation, maternal age, presentation of twin B, chorionicity or the national perinatal mortality rate of the mother's country of residence. It was found, however, that the second twin was more likely than the first twin to have the primary outcome.¹ The authors of the study concluded that planned CD was not associated with better neonatal or maternal outcomes than planned VD.

While this study was the first (and will likely be the only comprehensive, large-scale RCT regarding mode of delivery in twin pregnancies), it leaves several questions unanswered. Among these questions is the significance of a weight discrepancy between the twins, the level of expertise deemed necessary of those managing multiple pregnancy births, VD of twins at less than the specified gestational age and women with previous CDs.

Interestingly, a secondary analysis of the results has shown that for pregnancies between 32+° and 36+6 weeks of gestation, a planned VD was associated with fewer adverse outcomes compared to planned CD (OR 0.62, 95% CI 0.37-1.03). Nonetheless, at gesta­tional ages of 37+° weeks and above, the rate of composite perinatal outcome was 2% in the planned VD arm versus 1% in the planned CD arm (OR 2.25,95% CI 1.06-4.77). While this may look as though CD may be favourable, we must remember that most twins are delivered well before 38 weeks. The authors of this secondary analysis concluded that ‘the absolute risks at term are low and must be weighed against the increased maternal risks associated with planned CD'.⁴

Following the publication of the TBS, several sub-analyses were performed.

Neonatal outcomes at two years of age were also assessed in the TBS cohort. Overall, 4,603 children from the initial cohort of 5,565 infants (83%) were included in the study. The authors found no significant difference in the outcome of death or neurodevelopmental delay (OR 1.04, 95% CI 0.77-1.41) and concluded that planned CD had no added benefit to children at two years of age compared with planned VD in patients with characteristics similar to the TBS cohort.⁷ A further paper explored whether maternal outcomes two years after delivery, such as urinary stress or faecal or flatus incontinence, were affected by planned mode of delivery in twins and found that women in the planned CD group were less likely to experience urinary stress incontinence compared with their VD group counterparts (OR 0.63, 95% CI 0.47-0.83), with no reported difference in the quality of life. No differences were found in faecal or flatus incontinence or in other maternal outcomes.⁸

Several years after the publication of the TBS, these results were further validated by the JUmeaux MODe d'Accouchement (JUMODA), a national prospective population-based cohort study in 176 maternity units in France.⁹ The inclusion criteria were quite similar to those of the TBS.

The Issues

Delivery of the Non-cephalic Second Twin

As mentioned earlier in this chapter, in uncomplicated DCDA or MCDA twin pregnancies after 32 weeks of gestation, if twin A is in cephalic presentation, regardless of the presenta­tion of twin B, no differences were found in the TBS between planned VD and planned CD. Yet the delivery of twin B is at times not straightforward, especially in the era of the Term Breech Trial when manual expertise of breech deliveries declined significantly.¹⁰ The main dilemma surrounds the optimal management of the non-cephalic twin B - whether an external cephalic version (ECV) should be attempted or whether total breech extraction should be preferred.

Several authors tried to assess the confidence level of trainees in obstetrics in VDs of twins. In one of the studies, out of a total of 417 residents only a third felt confident managing the breech second twin and 28% did not feel comfortable managing the breech second twin post-residency.¹¹ The solution to training gaps might be simulations, yet further studies are needed in order to determine the optimal training method for managing the second breech twin.

In 1983, a small study advocated ECV of the second non-vertex twin after delivery of the first twin in order to achieve delivery of the second twin in a vertex presentation.¹² The ECV was successful in 18/25 (72%) sets of twins after successful delivery of the first vertex twin and was not associated with increased perinatal complications.¹² Subsequent to this, other investigators published similar findings. Others, however, have reported a significantly higher incidence of VD with breech extraction (with or without internal podalic version) compared with ECV for the second non-vertex twin.

Combined Delivery

The unique entity of combined delivery should also be addressed. Several authors have published their findings through the years regarding risk factors for CD of the second twin following VD of the first. According to past reports, the rate of combined delivery is 5-10%. Most of these findings come from small-sized, retrospective studies which showed that malpresentation of the second twin is associated with higher rates of combined delivery. Combined deliveries were also associated with a higher incidence of maternal and neonatal infectious morbidity.

Recently a sub-analysis of the TBS concerning combined deliveries was published.¹³ Of 842 cases where the first twin was delivered vaginally, 59 (7%) had CD for the second twin. The rate of non-cephalic presentation of twin B was more than twofold higher in the combined delivery group and the likelihood of spontaneous version of twin B (a different presentation at delivery compared to the presentation at randomisation) was also higher in the combined delivery group. In a multivariable regression model, breech presentation was not significantly associated with combined delivery (aOR 0.99, 95% CI 0.36-2.67), in contrast to transverse/oblique lie (aOR 43.74, 95% CI 15.37-124.49). Combined deliveries were more likely to be associated with fetal/neonatal death or serious neonatal morbidity (13.6% vs 2.3%, p < 0.001), five-minutes Apgar score < 7, NICU admissions, abnormal level of consciousness and prolonged (≥ 24 hours) assisted ventilation. Combined delivery was also associated with fetal/neonatal death or serious neonatal morbidity (aOR 5.14, 95% CI 1.95-13.53). The authors conclude that the data can be used for counselling couples who consider trial of labour and imply that training, probably including simulation, may prove beneficial for those practising vaginal twin births.

Time Interval between Delivery of Twins

It was previously believed that the time interval between the deliveries of twins should be no longer than 30 minutes, as a prolonged interval placed the second twin at risk of asphyxia from decreased placental circulation, as well as decreased likelihood of VD. In the TBS the mean inter-twin delivery interval was 8 minutes with a range of 1 to 33 minutes.¹

Recent studies report conflicting results. For example, one study which examined the effect of inter-twin delivery interval on neonatal outcome found that in cases where both twins were delivered vaginally (n = 151), there was no significant correlation between the inter-twin delivery interval and umbilical cord arterial pH or Apgar scores at 1, 5 and 10 minutes of twin B.¹⁴ Another study which examined the association between inter­twin delivery interval and short-term perinatal outcomes found that a composite adverse neonatal outcome (at least one of perinatal death, admission to neonatal intensive care unit (NICU), endotracheal intubation, Apgar < 7 at five minutes and cord lactate > 4.0 mmol/L) occurred in 201/345 (58.2%) of the twins and 7 (2%) had a CD for the second twin. For the second twin delivery interval was associated with higher cord lactate, and low Apgar scores and CD were more frequent with intervals > 30 minutes. The predictors of adverse outcome were gestational age, abnormal fetal heart rate tracing and breech delivery of twin B.¹⁵

Most of the studies prove hard to interpret, since most of them do not correlate mode of delivery and the set-up (operating room or delivery room) with a longer twin-to-twin interval. Naturally, if there is an abnormal fetal heart rate tracing and an urgent CD is necessary, the inter-twin delivery interval will be longer than an uncomplicated VD, if only because of the need to transfer to the operating room, administer anaesthesia and so forth. As such, a longer interval may be associated with poorer outcomes, but this association is mainly confounded by the primary indication to intervene rather than the longer time that was the result of an intervention. It is safe to assume that there is probably some association between the inter-twin delivery interval and deterioration of Apgar scores and umbilical cord pH, yet a clear threshold is hard to establish and the correlation is probably weak. The UK National Institute for Health and Care Excellence (NICE) guideline uses a 20-minute interval as a cut-off for delivery of the second twin if there is an abnormal (suspicious or pathological) fetal heart rate tracing.¹⁶

Breech-Presenting Twin (Twin A)

The literature regarding the recommended mode of delivery of a non-cephalic twin A is scarce. First, singleton vaginal breech deliveries have been a matter of debate until the publication of the Term Breech Trial. Another concern with a breech twin A and a cephalic twin B is the potential rare complication of locked twins. This complication is uncommon with an estimated frequency of 1:500-1:800, but the mortality associated with fetal entangle­ment is extremely high.

A systematic review of 1 small RCT (60 twin pairs) and 16 observational studies (3,167 twin pairs) did not find significant differences between non-cephalic twin As delivered via CD or VD. Nonetheless, the authors only compared the rates of neonatal mortality and five- minute Apgar scores < 7, and for the purpose of non-cephalic twins A included only 8 low- quality observational studies. The authors concluded that ‘No final conclusion can be drawn due to the small sample sizes and statistical limitations of the included studies.'¹⁷

The Term Breech Trial was published in 2000 and changed obstetrical practices around the world.¹⁰ In this multinational, multicentre study, 2,088 women with singleton gestation in breech presentation were randomised to planned VD versus planned CD. The authors found that perinatal mortality, neonatal mortality or serious neonatal morbidity were lower in the planned CD group (1.6% versus 5.0%, p complications such as twin-twin transfusion syndrome, twin anaemia-polycythaemia sequence, twin-reversed arterial perfusion and selective fetal growth restriction. Even in the absence of recognisable monochorionic-specific complications, monochorionic twins usually experience a higher rate of adverse neonatal outcomes.

Several studies have attempted to address the issue of mode of delivery of MCDA twins, usually through retrospective analysis. Most studies compared delivery outcomes of MCDA twins with those of DCDA twins, and most did not find significant differences between these groups. Nonetheless these studies were retrospective, with various sample sizes. Most importantly, these studies do not provide practical information and tools that can be used in clinical practice to counsel couples regarding the optimal mode of delivery based on multiple factors, including chorionicity.

In the TBS 23-25% of women had monochorionic twins and approximately 2% had unknown chorionicity. While the analysis considered chorionicity as a co-factor in the primary outcome, no direct analysis was performed of the impact of mode of delivery in monochorionic twins.¹ Recently a sub-analysis of the data regarding MCDA twin was completed.²⁰ The authors found no differences between planned VD and planned CD for MCDA twins.

Preterm Birth and Low Birthweight

The published literature on mode of delivery for preterm and/or low-birthweight twins is very conflicting with some studies of preterm twins showing adverse outcomes associated with VD while others do not.

A systematic review and meta-analysis of the safest mode of delivery for preterm twins when twin B is in non-cephalic presentation found no difference between twins delivered by VD or CD in cephalic/non-cephalic twin pairs at 24+° to 27+6 weeks. Nonetheless, the confidence intervals were wide due to the small sample size, and the 24+° to 27+6 weeks sample was quite large, indicating significant heterogeneity and variety between the studies.²¹

Another systematic review and meta-analysis included 15 studies with more than 12,000 infants. Caesarean delivery was associated with a 41% decrease in odds of death between 23+° and 27+6 weeks (OR 0.59, 95% CI 0.36-0.95, NNT 8), especially under 24+6 weeks of gestation (OR 0.58, 95% CI 0.44-0.75, NNT 7). The odd ratios for 25+° weeks and above were not significant. Caesarean delivery was also protective with regards to severe intraventricular haemorrhage between 23+° and 27+6 weeks, yet this effect, as for mortality, was mainly visible in lower gestational ages.²²

The NICE guidelines suggest offering CD for preterm twin deliveries between 26 and 32 weeks when twin A is in a non-cephalic presentation. Prior to 26 weeks, their recommen­dation is that the decision should be individualised.¹⁶ The SOGC guidelines recommend VD of both twins as long as their individual weights exceed 1,500 grams and twin A is in a cephalic presentation. Between 500 and 1,500 grams there is no recommendation, as the writers acknowledge the lack of good-quality literature.¹⁸

To conclude, neonatal outcomes in twin deliveries are highly variable and depend not only on mode of delivery, but also on neonatal weight, presentations, level of neonatal care and advances in neonatal resuscitation through the years. With current knowledge, clear gestational age and birthweight thresholds are difficult to determine.

Previous Caesarean Section (Twin VBAC)

While the risks and potential adverse outcomes of trial of labour after a previous CD (TOLAC) were extensively studied for singleton gestations, data for women with twin gestation and a history of CD are less clear.

Two meta-analyses recently published have addressed twin TOLAC. In the first one, the authors included 10 studies for a total of 2,336 trials of labour and 5,736 CDs. They reported that the pooled rate for successful TOLAC was 72.2% (95% CI 59.7-83.2%) and the risk for uterine rupture during TOLAC was 0.87% (95% CI 0.51-1.31%). They found TOLAC was associated with higher risk of neonatal death (RR 3.02, 95% CI 1.07-8.54). The risks of uterine dehiscence, blood transfusions and hysterectomy were comparable, though the risk of infectious morbidity was higher in the CD group. The authors concluded that twin TOLAC is associated with a high success rate and a low rate of uterine rupture, and that the higher neonatal mortality rate may be attributed to prematurity.²³

The second meta-analysis pooled data from 11 cohort studies (8,209 twin gestations), of which 2,484 were intended for planned VD and 5,725 for planned CD. Twin TOLAC was associated with a higher risk of uterine rupture (OR 10.09, 95% CI 4.30-23.69; I2 = 68%) when compared to twin CD. Nonetheless, when compared with singleton TOLAC, twin TOLAC was not found to differ with regard to the rate of uterine rupture (OR 1.34, 95% CI 0.54-3.31). None of the other adverse outcomes were found to be different between twin TOLAC and CD, and the success rate of twin TOLAC was similar to that of singleton TOLAC (OR 0.85, 95% CI 0.61-1.18).²⁴ To conclude, it seems that twin TOLAC is a reasonable and safe option for women carrying twins who had a previous CD and that the risks and success rates are similar to those reported for TOLAC in singleton pregnancies.

Higher-Order Multiple Pregnancy

Several authors have attempted to assess the feasibility of VD in triplet pregnancies. All these studies are observational and are limited by small sample size. As for the guidelines, similar to MCMA twins, the NICE, ACOG and SOGC guidelines are uniform in their recommendation for CD in the case of triplets or higher-order multifetal gestations.^16,18,19

Management Recommendations

• Twin delivery should be undertaken by an experienced practitioner competent in twin deliveries.

• Ultrasonographic examination is a useful adjunct prior to delivery (in order to assess fetal presentations, well-being and estimated fetal weights) and after delivery of the first twin in order to establish the fetal lie and presentation of the second twin. Depending on the gestational age, up to 20% of second twins will spontaneously change presentation once the first twin is delivered.¹²

• Intravenous access should be secured and blood sent for group and screen in anticipation of post-partum haemorrhage.

• The use of epidural, although not mandatory, is highly recommended. It is the authors' opinion that given the high likelihood for obstetrical intervention such as internal podalic version, breech extraction and/or operative delivery, adequate analgesia is essential.

• Continuous electronic monitoring is highly recommended. In order to increase maternal comfort by reducing the number of abdominal straps, and to better differentiate the two twins, the authors prefer a fetal scalp electrode on the leading twin once the membranes are ruptured.

• The use of oxytocin for augmentation may be advantageous, especially after the delivery of the first twin.

• We use double set-up (delivery in the operating room) for all twin gestations. The double set-up arrangement allows for a safe VD in the same setting of the delivery room, with extra care taken to provide for spousal chaperoning, skin-to-skin contact and so forth. On the other hand, if urgent obstetrical intervention is needed, all necessary personnel are in place and conversion to a CD is prompt.

• The third stage of labour should be managed actively to prevent blood loss, using oxytocin, uterine massage and other uterotonics as needed.

Key Points

• In women with uncomplicated DCDA or MCDA twin gestation, between 32 and 38 weeks of gestation, twin A in a cephalic presentation, and estimated fetal weights between 1,500 and 4,000 grams, a trial of VD should be offered.

• In women with twin and breech twin A, a caesarean section should be offered.

• Delivery of the second non-cephalic twin is probably safer using total breech extraction (with or without internal podalic version), rather than ECV.

• Although there is probably some association between the inter-twin delivery interval and deterioration of Apgar scores and umbilical cord pH, an exact threshold of the optimal time interval between the delivery of twins is not established.

• After delivery of the first twin, if there is concern about the well-being of the second twin, usually due to abnormal fetal heart rate tracing, delivery of the second twin should be expedited.

• There is scarce evidence regarding mode of delivery for MCMA twins, yet most guidelines recommend a caesarean section.

• The current data and recommendation regarding mode of delivery for MCDA twins suggest that it is no different than DCDA twins.

• Clear data concerning mode of delivery in preterm and low-birthweight twins is lacking, and individual management plans are recommended based on presentation, estimated fetal weight, gestational age, parity and so forth.

• Women with single previous low-segment caesarean section may be considered for a trial of VD in their subsequent twin gestation.

• There is scarce evidence regarding mode of delivery for higher-order multiple pregnancies, yet most guidelines recommend a caesarean section.

References

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