RESULTS
The total number of fetal records from 2011 to 2014 in the JECS was
104,102. Of these, 1,994 and 3,278 records were excluded for multiple
gestations and insufficient DII data, respectively. Then, 10,432
participants were excluded for having insufficient data. After applying
our inclusion criteria, 88,398 participants were eligible for the
present study and were then categorised into two groups based on the
presence or absence of endometriosis (self-reported) (n=3,249,
endometriosis group; n=85,149 without endometriosis group). Finally,
both groups were divided into five categories according to quintiles of
their DII score (Figure 1).
Table 1 summarises the basic characteristics of the participants
according to the presence of endometriosis. The mean maternal age and
maternal age categories were significantly different between the two
groups (p<.001 and p<0.001, respectively). The mean
DII was significantly higher in the non-endometriosis group
(p<0.001). In the endometriosis group, the rate of uterine
myoma, adenomyosis, and ART pregnancy were significantly higher than
those in the non-endometriosis group. The categories of maternal
education, household income, and BMI were significantly different
between the two groups (p<0.001, p<0.001, and
p=0.031, respectively).
Table 2 summarises the trend of obstetric outcomes for both groups
according to the DII category. The prevalence of PTB <37 and
<34 weeks, LBW <2500 g, and HDP were 4.5%, 0.9%,
7.9%, 0.5%, and 2.8%, respectively, for the non-endometriosis group,
and 6.2%, 1.2%, 10.0%, 0.7%, and 3.2%, respectively, for the
endometriosis group. Among women with endometriosis, the incidence of
LBW <2500 g decreased in the DII group (p=0.008). Among women
with endometriosis, the incidence of PTB <34 weeks and LBW
<1500 g significantly decreased in the DII group (p=0.040 and
p=0.003).
Table 3 summarises the aORs of obstetric complication according to DII
category for both the endometriosis and non-endometriosis group, with Q1
(most pro-inflammatory category) as the reference. The multiple
regression analysis shows decreased risk for PTB <34 weeks in
Q3 (aOR 0.77, 95% CI 0.62–0.97), Q4 (aOR 0.77, 95% CI 0.61–0.96),
and Q5 (aOR 0.80, 95% CI 0.64–0.998) for the endometriosis group. For
the endometriosis group, Q5 groups had significantly decreased risk of
PTB <34 weeks (aOR 0.35, 95% CI 0.12–0.99) and LBW
<1500 g (aOR 0.13, 95% CI 0.03–0.61). For women with
endometriosis without ART, Q5 still significantly decreased the risk of
PTB <34 weeks (aOR 0.25, 95% CI 0.07–0.83) and LBW
<1500 g (aOR 0.07, 95% CI 0.01–0.60).