Operative characteristics and pregnancy outcome
The operative characteristics and pregnancy outcomes were showed in
table 2. There was no significant difference between the two groups in
the operative characteristics. The cervical length before procedure and
the total ablation time were non-significant. The rate of preterm birth
before 37 weeks, before 34 weeks, before 32 weeks ,before 30 weeks and
before 28weeks were similar between the two groups. The complication
after the procedure in the two group were non-significant different,
including post-procedural complication and perinatal complication.
Termination of pregnancy(TOP) due to fetal serious oligohydramnios or
structural anomaly of the co-twin. TOP occurred in 8 cases in fetal
abdomen group and 3 cases in fetal back group. The TOP rate was
non-significant different in the two group(6.9% vs 10.3,p =0.53). The characteristics about delivery were non-significant
different between the two groups too, including the neonatal gestational
age and the rate of cesarean section.
The relation of RFA technique was assessed by means of survival
analysis. Multivariate Cox regression analysis indicated that the
survival curve of fetal survival time interval after the procedure
between the two needle insert angles were statistically different, while
set several related variables as covariates, including gestational age
at the procedure, cervical length, indications and total ablation time.
(P <0.001)(Figure 2). The model characteristic was
showed in table 3, cervical length and the gestational age before the
procedure were significant predictors for the period between RFA
procedure and delivery(table 3).
Risk of adverse outcome of the RFA procedure: multivariable
analysisMultivariable logistic analysis was conduct to assess the relation of
the risk of perinatal adverse outcome and several factors, include
different RFA needle insert angle, gestational age at the RFA procedure
cervical length before the procedure, the overall ablation time, while
controlling for maternal age and indication for RFA as potential
confounders. The result showed that compared to live birth at term, the
risk of miscarriage,termination and IUFD were statistically higher when
the cervical length was less than 35mm( Table 4). The model revealed
that the subject cervical length less than 27mm were 33.416 times to
report adverse perinatal outcome than those whose cervical length more
than 35mm. While other factors were non-significantly related with a
higher rate of adverse perinatal outcome, including miscarriage, IUFD,
termination and preterm birth.Factors associated with risk of advertise outcomeWe further assessed the association between the indication for RFA and
the risk of adverse post-procedure complication. Overall, 49(33.8%) RFA
were conducted due to TTTS, 30(20.7%) due to anomalous co-twin,
23(15.9%) due to sIUGR, 19(13.1%) due to TRAP, 12(8.3%) due to
excessive number of fetuses, 11(7.6%) due to TTTS accompanied by sIUGR,
1(0.7%) due to TAPS. Table 5 showed the outcome variables stratified by
indication.
Table 5 showed the outcome variables stratified by indication.The
gestational age at the procedure was significantly different within the
indications, those who underwent RFA for TRAP and excessive number of
fetuses were lower than monochorionic twin pregnancy complications.
Women who underwent RFA for TTTS had a similar gestational age at the
procedure as who underwent RFA for TTTS, TTTS & sIUGR. The interval
between RFA procedure and delivery was statistically different within
the indications, the interval of those who underwent RFA for excessive
numbers of fetuses was longer than other indications. The preterm
labor(<37weeks) rate was statistical different within the
indications, those who underwent RFA for TTTS was later than any other
indications. Even though there was non-significantly different during
the indications, the gestational age at delivery of TTTS was lower than
other indications.Even though there was non-significant difference
within the indications, the pregnancy with live born fetus showed a
higher trend in IUGR &TTTS and excessive number of fetuses than other
indications.
In order to assess the impact of gestational age at the RFA procedure on
perinatal outcome, we conduct a subgroup analysis, according to whether
the procedure was performed before 24weeks or after 24 weeks, the age of
viability2.(table 6)
Overall, 117 RFA procedures were performed before 24 weeks gestational
age, and 28 RFA procedures were performed after 24 weeks gestational
age. In order to avoid serve preterm birth, the RFA procedure were
conducted before 28 weeks. There was no significant difference between
the subgroups with regard to total ablation time, alive rate, adverse
perinatal outcome rate, gestational age at delivery and preterm labor.
The interval between RFA procedure and delivery was statistically
shorter in post-viability group than in pre-viability group.