Interpretation and comparison to current literature
MCDA twins are considered to be at highest risk of perinatal morbidity
and mortality because of acute hemodynamic intrapartum changes mediated
by placental vascular anastomoses[10]-[11].
However, due to a lack of evidence, there is no clear consensus
regarding the optimal mode of delivery in uncomplicated twins. Despite
the relevance of chorionicity, most studies addressing the contribution
of the mode of delivery in perinatal morbidity have not been stratified
accordingly. Furthermore, relevant aspects such as the mode of onset of
labor or long-term neurodevelopment have not been taken into
consideration.
To date, only eight studies have taken chorionicity into account when
analyzing the optimal mode of delivery in uncomplicated twins, with
disparate designs and neonatal morbidity
criteria[16]-[23]. Of the eight studies, four
were secondary analysis of previous studies. None of them considered the
mode of onset of labor in the TOL group or long-term NDI. The most
relevant data of each study are summarized in table 6. Our findings are
consistent with those reported in the above-mentioned studies,
demonstrating that attempted vaginal delivery for uncomplicated MCDA
twins is a safe management option, when performed by a trained obstetric
team, and has a low perinatal morbidity rate. Therefore, when first twin
is in vertex presentation, PCS does not seem to be the strategy to avoid
perinatal adverse events in uncomplicated MCDA pregnancies after 32.0
weeks, but rather shows a slight increase in them (aOR 1.36, 95% CI
0.24-7.81).
The gestational age at delivery in the pregnancies included in the
different studies is highly variable, ranging from 24.0 to 38.6 weeks.
In our study, we decided to include moderate to late preterm births
(32.0 – 36.6 weeks) to avoid masking a protective effect of cesarean
section in that range of gestational age.
The impact of the mode of delivery in twins on 2-year-neurodevelopment
was studied by Asztalos et al. in 2016[26]. The
authors performed a secondary analysis of the Twin Birth Study , a
large randomized controlled trial designed to compare planned vaginal
delivery and PCS[5]. This study finally included
2,323 pregnancies, of which 555 were MCDA. Although they do not stratify
the data in relation to chorionicity, the authors conclude that a policy
based in PCS provides no benefit to children at 2 years of age [5.99%
vs. 5.83%, OR 1.04 (95% CI 0.77-1.41), p=0.79]. Our study yields
similar results, although the NDI rate is slightly higher in PCS group
compared to TOL and their different onset modalities (spontaneous or
induced). However, the rate of 2-year-NDI is similar to that reported by
other authors when a selective analysis of MCDA pregnancies is
performed[27].