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.