4. Discussion
In this cohort study of women pregnant with twins, delivering a
gestation age between 32 weeks 0 days and 38 weeks 6 days with the first
twin in cephalic position, we found that neonatal outcomes between VB
and CB were similar in term pregnancies whereas adverse neonatal
outcomes were increased in the VB group in preterm second twin.
In a large-scale retrospective study, it was concluded that vaginal twin
delivery appears safe if experienced staff monitor birth weight
differences, birth interval, and blood values (15). In a comprehensive
randomized study, no difference was observed between fetal and neonatal
mortality rates and severe neonatal morbidity when comparing VB and CB
in twin pregnancies between 32 and 38 weeks with the first twin in
vertex presentation (4,14). A recently published prospective cohort
study found that an increased risk on adverse neonatal outcomes was
seen after planned CB compared to planned VB at a gestation age of 32
weeks 0 days to 36 weeks 6 days. In addition, no difference was found
between the groups after 37 weeks (10). In another study, no difference
was observed between the groups for term pregnancies, but preterm
pregnancies were found to have significantly higher rates in the VB
group (13). Another study found that perinatal mortality did not differ
statistically significant between planned CB and planned VB in preterm
twins but at term, a planned CB may result in less asphyxia and
trauma-related outcomes (16). In our study, there was no difference in
ENMR in the term pregnancy groups when comparing CB and VB, but this
rate was significantly higher in the VB group in the preterm group.
As for neonatal outcomes, it seems that second twins displayed higher
morbidity rates (9,17,18). In our study, all the first twins were
delivered via VB in group 1, and 17.97% of the second twins were
delivered via emergency intrapartum cesarean sections, which is similar
to the VB group in the study performed by Goossens et al. (intrapartum
CB rate of 19.7%) (16). Early neonatal deaths occurred in two of the
second twins who had to be delivered via emergency intrapartum cesarean
sections in the VB group, and the ENMR in this group was 2.24%, while
this rate was 0.97% in the CB group for the second twins. However, in
the subgroup analysis, early neonatal deaths in both groups were
observed in the preterm pregnant group. Unlike in our study, Barrett et
al. (11), who reported no difference in terms of early neonatal
mortality after CB and VB in the preterm pregnant group.
Zafarmand et al. (19) identified gestational age at birth as a strong
prognostic factor for the outcomes of neonates, depending on the planned
mode of birth. They also stated that from 32 to 37 weeks, a planned VB
seems favourable, while from around 37 weeks on, a CB might be safer. In
our study, early neonatal mortality was observed in both the VB and CB
groups at 32–37 weeks but not over 37 weeks.
When VB is attempted, the capacity for immediate CB is important in the
event that complications necessitating urgent birth arise (e.g.,
prolapsed umbilical cord, non-reassuring fetal heart rate, no descent of
the fetal presentation, failed breech extraction, or failed internal
podalic or external cephalic version, cervical retraction, prolapse of
an arm and placental abruption). Our study showed that main indication
for cesarean for the second twin was the failure of intrauterine
manoeuvres. In the main, emergency situations presenting more than one
obstetrical complication were responsible for this uncommon practice
(20). Studies have shown that in twin pregnancies, the incidence of
adverse perinatal outcomes in twin pregnancies delivered with emergency
intrapartum cesarean sections is higher than in planned CBs (21-23). Our
study also showed high ENMR results in twins with emergency intrapartum
cesarean sections in the VB group, which is similar to the results of
literature.
Grossman et al. (24) found that maternal morbidity increased in the VB
group compared to the planned CB group. Also, in this study, the highest
rate of adverse outcomes was seen in twins who underwent CB after failed
induction of labor (24). Also, Mei-Dan et al. (14) found that planned
VB group had more antepartum hemorrhage (1.9% vs 0.6%) and maternal
complication (2.4% vs 0.1%) compared with the planned CB group.
Conversely, in another study was found that in twin pregnancies with
planned VB, CBs for the second twin and for both twins are associated
with higher risks of severe acute maternal morbidity than VB (3). The
multicentre retrospective study of Wenckus et al. (8) comparing maternal
and neonatal outcomes in twins undergoing a trial of labor versus
prelabor caesarean, there was an increased risk for postpartum
haemorrhage and blood transfusion for the trial of labour. In our study,
we did not find any difference in terms of maternal morbidity/mortality
according to the mode of birth.
Although the literature is controversial, inter-twin weight discordance
>20% was found to be a risk factor for increased perinatal
morbidity of second twins (25). However, Peaceman et al. (26) emphasized
that the route of birth does not influence neonatal outcomes when
assessing weight discordance above 20%. In our study, there were no
differences in terms of weight discordance in twin birth according to
the mode of birth.
As a limitation, the small number of study population and retrospective
collection of the data may be considered as weakness of our study. The
strength of our study is that it evaluates a controversial issue.