Results:
From November 2015 to December 2017, 2539 women underwent an IVF cycle
with their own eggs. Of these cycles, 121 were abandoned before egg
collection or had no eggs collected. On three occasions there was
failure to obtain sperm. There were 78 cycles with complete failure to
fertilise and two with failed cleavage. Mature oocyte cryopreservation
was performed for 17 patients and there were 8 cycles where no eggs were
suitable to inject following denudation for ICSI. There were 21 cases of
freeze all embryo cycles and 11 where no embryo transfer was performed
due to abnormal development. Three surrogacy cycles were excluded as
were two cycles which were lost to follow up leading to no outcome
information being available. We also excluded 15 cycles where both TLI
and SC incubators were used. This resulted in a total of 2258 cycles
included in this retrospective analysis, of which 1219 were in the TLI
arm and 1039 in the SC arm (figure 1).
Table 1 outlines the baseline characteristics of the two groups for
comparison. As reported previously 4, there was a bias
to older patients in the TLI group where the mean age was 35.15 years as
compared with 33.47 years in SC (MD, 1.68 years, 95% CI 1.31 to 2.05).
Despite being older, the women in the TLI arm had more oocytes
retrieved, with a mean of 12.15 oocytes vs 10.87 oocytes for SC (MD
1.28, 95% CI 0.74 to 1.82). Age and number of oocytes were therefore
adjusted for when analysing the outcomes. The proportion of cycles that
had a transfer performed was similar between the two groups, as was the
mean number of embryos transferred. However the proportion of cycles
with embryos available for cryopreservation (TLI 49.38 % vs SC 43.79%,
OR 1.25, 95% CI 1.06 to 1.48, p = 0.008) as well as the mean number of
embryos cryopreserved (TLI 1.37 ± 2.03 vs SC 1.10 ± 1.68, MD 0.08, 95%
CI 0.10 to 0.41, p = 0.001) was higher in the TLI group. The embryo
utilisation rate was also higher in the TLI group, but this did not
reach statistical significance (TLI 37.08% vs SC 36.29%, OR 1.03, 95%
CI 0.97 to 1.11, p = 0.323)
Table 2 outlines the clinical outcomes in the two groups. The clinical
pregnancy rate per cycle was significantly higher in the TLI group (TLI
46.84% vs SC 41.87%, OR 1.22, 95% CI 1.04 to 1.45, p = 0.017). There
was no significant difference in the multiple pregnancy rate (TLI 6.48%
vs 4.83%, OR 1.37, 95% CI 0.79 to 2.37, p = 0.267). There was a
significantly higher live birth rate per cycle in the TLI arm (TLI
39.87% vs SC 38.02%, OR 1.08, 95% CI 0.91 to 1.28, p = 0.039). After
adjusting for the baseline characteristics of age and number of oocytes
which had been noted to be significantly different between the TLI and
SC groups, the live birth rate was still significantly higher in the TLI
group (aOR 1.20, 95% CI 1.01 to 1.44, p = 0.040).
As noted above, a higher proportion of cycles in the TLI arm had embryos
available for cryostorage which in turn translated to a non-significant
increase in the proportion of women who had an embryo available in
cryostorage following an unsuccessful fresh embryo transfer (TLI 41.80%
vs SC 36.69%, OR 1.24, 95% CI 0.99 to 1.55, p = 0.058). This is turn
led to a non-significant trend towards a higher number of frozen embryo
transfers being performed in the TLI arm (TLI 1.25 ± 0.90 vs SC 1.22 ±
0.90, OR 0.03, 95% CI -0.12 to 0.19, p = 0.707). There was no
significant difference in the live birth rate per frozen embryo transfer
(TLI 30.96% vs SC 30.39%, OR 1.03, 95% CI 0.74 to 1.42, p = 0.377).
The cumulative live birth rate per cycle after taking into account both
fresh and frozen embryo transfers from the study period was on initial
analysis not significantly different between TLI and SC groups (TLI
50.29% vs SC 46.78%, OR 1.15, 95% CI 0.97 to 1.36, p = 0.125).
However, upon adjusting for age and number of oocytes, the cumulative
live birth rate was significantly higher in the TLI group (aOR 1.24,
95% CI 1.04 to 1.48, p = 0.016).