Objective To investigate the association between the atherogenic index of plasma (AIP) during the third trimester and the prevalence of preeclampsia (PE) among Tibetan pregnant women residing in high-altitude regions.

Methods A retrospective cross-sectional study was conducted on singleton pregnancies admitted to Chaya County People's Hospital, Changdu City, Xizang Autonomous Region, from January 2023 to May 2025. Participants were divided to PE or control groups according to established diagnostic criteria and further stratified into AIP tertiles: Q1 (AIP ≤ 0.79), Q2 (0.79 ＜ AIP ≤ 1.16), and Q3 (AIP ＞ 1.16). Baseline characteristics, laboratory parameters, and PE prevalence were compared across groups. Multivariable Logistic regression was employed to assess the association between AIP and PE, with restricted cubic splines used to characterize the dose–response relationship.

Results Compared with controls, the PE group had significantly higher pre-delivery body mass index (pre-BMI), triglycerides (TG), serum uric acid (UA), blood urea nitrogen, serum creatinine, and AIP levels, along with elevated rates of cesarean section, low birth weight (LBW), neonatal asphyxia, and intrauterine fetal demise (all P ＜ 0.05); HDL-C levels and neonatal birth weight were significantly lower (both P ＜ 0.05). Across AIP tertiles, significant differences were observed in pre-BMI, residential altitude, hemoglobin, TG, LDL-C, HDL-C, UA, neonatal birth weight, and the incidence of PE, preterm birth, cesarean section, and macrosomia (all P ＜ 0.05). Trend analyses revealed that as AIP increased, pre-BMI, TG, LDL-C, UA, neonatal birth weight, and the incidences of PE, cesarean section, and macrosomia rose progressively, whereas residential altitude, hemoglobin, HDL-C, and the incidence of preterm birth declined (all P ＜ 0.05). Multivariable logistic regression demonstrated a positive association between AIP and PE prevalence (OR = 2.97, 95% CI: 1.44–6.15, P = 0.003), with a significant dose–response relationship (P for trend ＜ 0.05). Restricted cubic spline analysis confirmed a linear association (P for non-linearity = 0.795).

Conclusion s Among Tibetan women with singleton pregnancies in high-altitude regions, AIP during the third trimester is positively and linearly associated with PE prevalence, providing a practical reference for perinatal metabolic management in this population.