Lower oxidative balance score is linked to increased miscarriage risk: findings from a case–control study

BACKGROUND: Oxidative stress (OS) may play a role in adverse pregnancy outcomes, including spontaneous miscarriage. This study aimed to assess oxidative balance score (OBS), ranging from 0 to 38, and related characteristics in women with spontaneous miscarriage compared to healthy pregnant women. METHODS: A case-control study was conducted at Kowsar Women's Hospital in Urmia, Iran, between June 2024 and March 2025. The case group included 152 women with spontaneous miscarriage, and the control group included 300 healthy pregnant women beyond 20 weeks' gestation. OBS, combining dietary and lifestyle antioxidant/pro-oxidant factors, was calculated and analyzed across tertiles. RESULTS: Total OBS was significantly lower in the case group compared to controls (20.25 ± 7.19 vs. 22.45 ± 6.67; p = 0.023), while dietary OBS did not differ significantly (p = 0.15). Lifestyle OBS was lower in the miscarriage group (p < 0.001), with reduced physical activity and higher smoking prevalence. Magnesium, selenium, and vitamin B6 intakes were also significantly lower in the case group (p-values = 0.047, 0.034, 0.042, respectively); However, after applying Bonferroni correction for multiple comparisons (adjusted α = 0.0026), none of the nutrient-level associations remained statistically significant. Higher tertiles of total and lifestyle OBS were associated with lower odds of miscarriage after adjustment for confounders (OR = 0.46, 95%CI (0.21- 0.99) and OR = 0.41, 95%CI(0.19- 0.88), respectively), while dietary OBS remained non-significant. CONCLUSION: Lower total and lifestyle OBS are associated with an increased risk of spontaneous miscarriage. OBS may serve as a useful marker for miscarriage risk assessment.