(1) Background: Diet holds a pivotal position in exacerbating or ameliorating chronic inflammation, which has been implicated in the pathogenesis of hyperemesis gravidarum (HG). However, no study has explored the association between dietary inflammatory potential and HG. This study aimed to investigate the potential correlation between following a pro-inflammatory diet and the likelihood of developing HG. (2) Methods: A total of 2033 Chinese pregnant women (mean age: 31.3 ± 3.4 years) were included in this cross-sectional study from April 2021 to September 2022 as part of the China Birth Cohort Study (CBCS). Dietary inflammatory index (DII) scores with 23 food components were constructed through dietary intakes collected via a reliable 108-item semi-quantitative food frequency questionnaire. HG was defined as a pregnancy-unique quantification of emesis (PUQE) score ≥13 points, severe nausea and vomiting leading to weight loss ≥5%, or being hospitalized for treatment due to the disease. The relationship between DII and HG was conducted utilizing binary logistic regression and restricted cubic spline regression. (3) Results: Overall, 8.2% (n = 167) of study participants had HG. The DII scores ranged from −4.04 to 3.82. After adjusting for potential confounders, individuals with the highest tertile of DII score had a higher risk of HG (OR = 1.65, 95% CI: 1.04, 2.62, Ptrend = 0.032). Such an association was stronger in those with pre-pregnancy overweight/obesity (Pinteraction = 0.018). (4) Conclusions: A higher DII score, which serves as a marker for a diet promoting inflammation, is correlated with an elevated risk of developing HG. This finding suggests that dietary recommendations for HG should focus on minimizing the DII through incorporating foods abundant in anti-inflammatory components.
