Objective To investigate the association between high-normal blood pressure in the first trimester and adverse pregnancy outcomes （APO）. Methods This cohort study recruited singleton and live birth pregnancies in the first trimester （6-13⁺⁶ weeks of gestation） from Shenzhen Maternity and Child Healthcare Hospital Affiliated from January 1，2020 to December 31，2022.The general data，mean blood pressure in the first trimester and APO were collected. According to the 2024 Chinese Guidelines for the Management of Hypertension，participants were categorized based on mean blood pressure in the first trimester into three groups： normotensive pressure group[<120/80 mmHg（1 mmHg=0.133 kPa）]，high-normal blood pressure group （120-139/80-89 mmHg），and hypertension group （≥140/90 mmHg）. Statistical analyses were performed using the χ² test，multivariate logistic regression，and sensitivity analysis. Results Compared with the normotensive group，the high-normal blood pressure group had a significantly higher overall incidence of APO （P<0.05）. Multivariate logistic regression analysis showed that high-normal blood pressure was an independent risk factor for gestational hypertension （aOR=6.22，95%CI 4.99-7.76） and preeclampsia （aOR=3.43，95%CI 2.85-4.13）. After excluding the women who developed gestational hypertension or preeclampsia in the second or third trimester，high-normal blood pressure remained significantly associated with increased risks of gestational diabetes mellitus （aOR=1.95，95%CI 1.42-2.67），preterm birth （aOR=1.17，95%CI 1.03-1.33），and small for gestational age （aOR=1.23，95%CI 1.11-1.44） （P<0.05）. Conclusions There is a significant dose-response relationship between first-trimester blood pressure level and the risk of APO. High-normal blood pressure，as defined by the Chinese guidelines，is an independent risk factor for APO.