Results
A total of 5,037 women were included in this study. Group G consisted of
4,484 patients and Group GP included 553 patients. After propensity
score matching, 520 patients in group G were matched by their
counterparts in group GP.
Patients’ overall demographics and baseline IVF characteristics were
presented in table 1 (left panel).
Significant differences were observed in terms of paternal age, AFC,
duration of infertility, No. of blastocysts vitrified, ovarian
stimulation protocol, endometrial preparation protocol, cycles of ET,
day of blastocyst transferred and the proportion of using top quality
blastocysts between two groups (P<0.05). Comparison after PS
matching was also listed in table 1 (right panel), all the baseline
characteristics became very comparable between two groups (P
> 0.05). The distributions of the standard differences
before and after PS matching were plotted (Figure S1). Standard
difference<0.1 was used as the threshold to indicate a
negligible difference in the prevalence of a covariate between exposure
groups.
Table 2 illustrates the outcomes of both groups before and after PS
matching. Group GP achieved significantly higher PR (57.3%vs47.3%,
OR:1.51, 95% CI: 1.18-1.93), LBR (47.9% vs 41%, OR:1.33, 95% CI:
1.04-1.7) and MPR (30.5%vs2.4%,
OR: 17.49, 95% CI: 7.49-40.81) than group G after PS matching. MR for
group GP were similar to group G (15.4% vs 13.4%, OR: 1.18, 95% CI:
0.73-1.9).
The outcomes of both groups stratified by age using a cutoff of 35 years
old were displayed in table 3. After matching, in women less than 35
years of age, PR (58% vs 50.1%,
OR:1.38, 95% CI: 1.05-1.82) and MPR (31.7% vs 1.9%, OR:23.81, 95%
CI: 8.54-66.43) were significantly higher in group GP than in group G.
However, there were no significant differences in
MR and LBR between two groups
(31.6% vs 27.4% and 48.7% vs 43.9%, respectively). Interestingly, as
for women 35 years of age and over, not only PR and MPR, but also LBR
(48.1%vs27.2%, OR:2.56, 95% CI: 1.3-5.03) were found significantly
higher in group GP than in group G. Adjusted OR for multiple pregnancy
in women aged 35 and over before PS matching was not given, because
multivariate GEE model was not available when the incidence of multiple
pregnancy is low in relation to 21 variables used in the adjustment
model.
Comparisons of two groups stratified
by cycles of ET were listed in table 4. For patients who received ET
less than 3 cycles, group GP had no differences in PR, MR and LBR
compared to group G. However, both PR (56.5% vs 42.2%, OR:1.79, 95%
CI: 1.22-2.61) and LBR (46.6% vs 35.4%, OR:1.6, 95% CI: 1.09-2.35)
were observed statistically higher in group GP when compared to group G
in patients undergoing at least 3 times embryo transfer. MPR were
consistently significantly higher in group GP than in group G
(31.7%vs5.6%, OR:7.97, 95% CI: 3.6-17.63) regardless of ET cycles.