Association between Maternal Dietary Inflammatory Index (DII) and abortion in Iranian women and validation of DII with serum concentration of inflammatory factors: case-control study

Previous studies have shown that some dietary components may be implicated in the etiology of spontaneous abortion. However, the possible relationship between diet-related inflammation and the risk of abortion has not yet been investigated. We examined the ability of the literature-derived Dietary Inflammatory Index (DII) to predict the abortion incidence in women suffering from recurrent abortion in a case-control study conducted from April 2010 to March 2011. This included 67 incident cases and 68 controls (frequency matched to cases by age) who attended infertility and miscarriage specialized centers in Tehran, Iran. The DII was computed based on dietary intake assessed using a validated and reproducible 168 item food-frequency questionnaire. Logistic regression models were used to estimate multivariable ORs adjusted for age, education, occupation, and body mass index. Subjects with higher DII scores (i.e., a more pro-inflammatory diet) had higher odds of abortion, with the DII being used as a continuous variable (ORcontinuous = 2.12, 95% CI: 1.02-4.43). When analysis was carried out with DII expressed as a dichotomous variable, women in the pro-inflammatory diet group (DII > 1.24) were at 2.12 times higher odds of having abortion compared with women in the referent group (DII ≤ 1.24) (ORDII>1.24/≤1.24 = 2.12; 95% CI: 1.02-4.43). In the same study, for every 1-unit increase in DII, there was a corresponding increase in interleukin-6 by 0.15 pg/mL, 95% CI (<0.01, 0.28). In conclusion, subjects who consumed a more pro-inflammatory diet were at increased odds of abortion compared with those who consumed a more anti-inflammatory diet.