INTRODUCTION
Endometriosis occurs in 10% of women of reproductive age, is
characterised by ectopic proliferation of the endometrial tissue of the
uterus, and is commonly associated with chronic pelvic pain and
infertility.1 It occurs in up to 50% of women with
infertility.2 A recent study has shown that
inflammation leads to the elevation of components of signalling pathways
such as mitogen-activated protein kinase in
endometriosis3,4; therefore, treatment for chronic
inflammation could be a potential target of therapy for endometriosis.
Although several clinical managements for infertility, including
surgical debulking of endometriosis lesion and assisted reproductive
treatment, have been proposed,5 a recent systematic
review and meta-analysis suggests that women with endometriosis are also
at risk of obstetric complications such as preterm birth (PTB) and low
birth weight (LBW),6 resulting in long-term sequelae
such as neurodevelopment disorders of offspring. Neurodevelopment
morbidity is thought to be affected by intrauterine inflammation and
earlier gestational age.7–9
Diet is thought to actively influence the regulation of chronic
inflammation. A high-calorie, high-fat diet (such as diets including
Western food), promotes inflammation, and consumption of Western food
exposes the body to recurrent inflammation.10Consequently, several diseases such as cardiovascular disease, diabetes
mellitus, thrombosis, asthma, and depression may
occur.11–13 By contrast, many vegetables and foods
rich in minerals, such as traditional Japanese food and Mediterranean
food, have anti-inflammatory effects.14,15 Recently,
the concept of pro-inflammatory and anti-inflammatory diets has been
reported. The dietary inflammatory index (DII) is used to assess the
inflammatory potential of an individual’s diet.16 The
DII has been proved to be associated with non-communicable diseases such
as cancer, cardiovascular disease, obesity, type 2 diabetes mellitus,
and asthma.17
In our previous study using the largest Japanese birth cohort study, we
reported that a high DII score (pro-inflammatory effect) before
pregnancy leads to leukocytosis during the first trimester and a low DII
score (anti-inflammatory diet) decreases the risk of PTB and
LBW.18 Therefore, changing one’s dietary habit for an
anti-inflammatory diet before pregnancy could potentially prevent these
obstetric complications. To our best knowledge, no study has examined
the correlation between prepregnancy dietary pattern and obstetric
outcome among women with endometriosis.
We hypothesised that a prepregnancy anti-inflammatory diet might reduce
the PTB risk, especially among women with endometriosis. Hence, this
study aimed to investigate the effect of prepregnancy anti-inflammatory
diet, by means of DII score, on obstetric outcomes among women with
endometriosis using the largest Japanese birth cohort study.