The Twin Birth Study

Here’s the RoshReview Question of the Week:

Which of the following needs to be met to undergo vaginal delivery with a monochorionic-diamniotic twin pregnancy with vertex twin A?

Check your answer and get a special RoshReview deal for listeners at the links above!


Actual title: A Randomized Trial of Planned Cesarean or Vaginal Delivery for Twin Pregnancy

https://www.nejm.org/doi/full/10.1056/nejmoa1214939 

Background:

  • Where was the study published?

    • NEJM, October 3, 2013

  • Why was the study done?

    • Tthrough the 1990s and 2000s there was a significant rise in twin births in the USA, likely attributed to advancing maternal age (when twinning is more common spontaneously) and the use of reproductive technology – ovulation induction and IVF.

    • In the wake of the Term Breech trial, as well as some observational studies looking at twins specifically, there was concern that breech birth risks could be extended to twins – and practice was changing!

      • In 1995, 53.9% of twin births were by CS. By 2008, this number was 75%. 

    • Not all observational studies were in agreement about the risk of “breech extraction” of a second twin, specifically – so a new study was planned and performed.

  • Who performed the study?

    • The “Twin Birth Study Collaborative Group” – a large multinational collaborative, but with the main site at the University of Toronto and funded by the Canadian Institutes of Health Research – the same funders that brought you the Term Breech Trial!

      • You’ll note a lot of similarities (but also some important differences!) between this study and the Term Breech Trial. We definitely recommend a compare-contrast session!

  • What was the research objective?

    • To compare the risk of fetal/neonatal death or serious morbidity between planned cesarean or planned vaginal delivery for twin pregnancies between 32w0d and 38w6d, if the presenting twin was in cephalic presentation. 

Methods:

  • Who participated and when?

    • Recruitment between December 13, 2003 and April 4, 2011 at 106 centers in 25 countries.

    • Enrolled 1392 patients in the planned cesarean group and 1392 patients in the planned vaginal delivery group.

  • Eligibility:

    • Needed to have:

      • Twin pregnancy between 32w and 38w6d

      • First twin in cephalic presentation

      • Both fetuses alive with EFW between 1500g and 4000g, confirmed by ultrasound within 7 days before randomization

    • Exclusions:

      • Monoamniotic twins

      • Lethal fetal anomalies

      • Other contraindication to labor or vaginal delivery (including 2nd twin being “substantially larger” than the first)

      • Prior cesarean with vertical incision or more than one LTCS

  • Management:

    • Delivery by cesarean or by labor induction was planned between 37w5d and 38w6d

    • If in the CD group, if the first twin delivered vaginally, then a c-section was attempted for the second twin if logistically possible.

    • In the VD group:

      • Continuous EFM was “recommended” during active labor

      • Use of oxytocin and epidural analgesia were left to OB provider discretion

      • After delivery of first twin, use of US was “encouraged” to check second twin presentation

        • If cephalic, amniotomy was delayed until head was engaged and SVD anticipated, unless for other OB indication

        • If non-cephalic, OB decided on best delivery option – spontaneous or assisted breech delivery, total breech extraction +/- internal podalic version, ECV and vaginal cephalic delivery, or intrapartum CD

      • Deliveries were attended by qualified OB experienced in twin delivery, defined as a OB who judged themselves to be experienced at twin delivery and whose department head agreed with this judgment (similarly to Term Breech Trial).

  • Outcomes:

    • Primary: fetal/neonatal mortality or serious neonatal morbidity, assessed up to 28 days after birth.

      • Morbidities included many of the same things in the Term Breech Trial, and were serious neonatal morbidities (for the sake of brevity, we won’t list them out).

    • Secondary: maternal death or serious maternal morbidity, assessed up to 28 days after delivery.

      • Again, this was very similar to the Term Breech Trial. 

    • A number of subgroup analyses were planned for the primary outcome, including by nulliparity; gestational age at randomization; maternal age; presentation of the second twin; chorionicity; and the perinatal mortality rate in the mother’s country of residence. 

Results

  • Who was recruited?

    • Outcome data was available for 1392 women (2783 fetuses/infants) in the cesarean group and 1392 women (2782 fetuses/infants) in the vaginal delivery group. 

    • Baseline characteristics were overall similar, and most patients (82.4%) underwent randomization between 32w0d and 36w6d. 

      • More than half of the infants in each group were born at 37w0d or later. 

        • Around 5-6% in each group were between 32w and 33w6d, and another 42% between 34w0d to 36w6d. 

      • The time from randomization to delivery was similar but slightly different between groups (12.4 vs 13.3 days).

  • In the planned CD group: 

    • 90% had CD

    • 1% had a combined vaginal-cesarean delivery, and 

    • 9% had both twins vaginally.

      • Almost 60% of the CDs were performed before the onset of labor.

  • In the planned VD group:

    • 56% delivered both twins vaginally, 

    • 4% had a combined vaginal-cesarean delivery, and 

    • 40% had a cesarean for both twins.

      • Of those in the VD group who had a CD, 67.5% of them were performed during labor (or another way to look at it, 32.5% had a CD prior to labor in the planned VD group).

    • 95% had an experienced OB present, according to the study definition

  • Primary Outcome:

    • The frequency of composite primary outcome did not differ between planned CD (60, or 2.2%) and planned VD (52, or 1.9%) groups.

      • The only variable that appeared to modify the risk of the primary outcome was earlier gestational age at randomization. 

      • The number of deaths in each group was 24 (0.9%) in CD group and 17 (0.6%) in VD group. 

        • 11 of these deaths in the CD group and 8 in the VD group were before labor onset.

    • In subgroup analyses, there was no significant interaction with the primary outcome with respect to parity, gestational age at randomization, presentation of the second twin, chorionicity, or national perinatal mortality rate. 

    • The second twin was more likely than the first to have the primary outcome, but this was not different between the groups. 

  • Secondary outcome:

    • There were no differences in primary maternal composite outcome rates (7.3% CD, 8.5% VD). 

Impact

  • What is the impact of all of this, and what are we doing now?

    • This paper certainly helped to encourage the training and planning of vaginal delivery of the second twin, including by breech delivery by stating that no increased risk was seen with a policy of planned vaginal delivery. 

      • In ACOG PB 231 on multifetal gestation, it notes that vaginal delivery of a non-cephalic second twin is reasonable, provided an OB with experience is present.

      • That’s key – it’s apparent in this paper that, compared with the Term Breech Trial, there was more emphasis on patient counseling / selection (i.e., 13 day median from randomization to delivery, protocolized assessment of EFW by US within 7 days, 95% presence of “experienced OB”). 

        • And this is heavily noted in the conclusions of the paper – stating “only centers that can provide OB management as specified by the protocol, including ability to perform a CD within 30 minutes if necessary” should undertake this.

  • Methodologically, this group responded to many criticisms of the Term Breech Trial:

    • An improved randomization scheme that was block-based, stratified by gestational age and parity.

    • Improved use of ultrasound and CTG in labor, as well as higher standard of care at all sites to prevent misappropriation of primary outcome.

    • More explicit counseling – happening weeks before delivery on average, rather than in labor!

  • And finally - and most importantly - this represents a well-selected, high-resource, best-case scenario work.

    • For our US listeners who mostly practice in centers where there is ability to perform cesarean within 30 minutes, the Twin Birth Study included:

      • Twins delivering between 32w0d and 38w6d

      • With EFW estimated by US within 7 days of delivery, ranging from 1500g - 4000g

        • Second twin not significantly larger (with expert opinion putting this around a max of 15% discordance)

      • Ability to perform CD within 30 minutes, and use CTG and intrapartum US

      • With someone with experience and ability to perform breech extraction and internal podalic version available