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
