Association between pre-delivery maternal red blood cell distribution width and birth weight discordance in twin pregnancies: a twin pregnancy cohort study

BackgroundTwin growth discordance, commonly defined as an inter-twin birth weight difference ≥20%, is linked to increased neonatal morbidity, but simple maternal laboratory markers to aid late-pregnancy risk assessment are limited. Red blood cell distribution width (RDW), a routine hematological parameter associated with inflammation and placental dysfunction, has been associated with adverse perinatal outcomes in singleton pregnancies; however, its role in twin growth discordance remains unclear.ObjectiveThis study aimed to examine the association between pre-delivery RDW measured within 1 week before delivery and twin growth discordance in a cohort of Chinese twin pregnancies.Study designThis retrospective cohort study included 1,714 women with twin pregnancies who delivered at the Gansu Provincial Maternity and Childcare Hospital between July 2020 and February 2024. Pre-delivery RDW was obtained from the last prenatal complete blood count within 1 week before delivery. Twin growth discordance was defined as inter-twin birth weight discordance ≥20%. Associations were assessed using multivariable logistic regression, with RDW modeled continuously and categorically (<14.3, 14.3–16.0%, and ≥16.1%). Restricted cubic spline, subgroup, and sensitivity analyses were also performed.ResultsOverall, 231 women (13.5%) had twin growth discordance. Compared with the lowest RDW category, the highest category was associated with increased odds of twin growth discordance after adjustment for maternal age, IVF status, chorionicity, gestational age, pregestational body mass index, parity, hypertensive disorders of pregnancy, gestational diabetes mellitus, and hemoglobin [odds ratio (OR) 1.89, 95% confidence interval (CI) 1.28–2.80; p = 0.001]. A significant trend was observed across RDW categories (p for trend = 0.001). RDW modeled as a continuous variable showed a borderline association after full adjustment (OR 1.06, 95% CI 1.00–1.12; p = 0.060). Restricted cubic spline analysis suggested a nonlinear association (p for non-linearity = 0.013). Results were similar using discordance ≥25% (OR 2.24, 95% CI 1.31–3.83; p = 0.003).ConclusionHigher pre-delivery RDW was associated with greater odds of twin growth discordance. Prospective studies with serial RDW measurements are needed to confirm these findings and determine their clinical relevance.