Psychological stress during the first trimester of pregnancy is one of the contributing factors associated with adverse pregnancy outcomes, including preterm birth. Comprehensive midwifery care during early pregnancy is expected to reduce maternal stress through health education, counseling, early detection of pregnancy complications, and continuous emotional support. Appropriate antenatal midwifery care may improve maternal adaptation to pregnancy and contribute to the prevention of preterm birth. This study aimed to determine the relationship between the implementation of midwifery care among first-trimester pregnant women and stress levels as an effort to prevent the risk of preterm birth at RSU GMIM Kalooran Amurang. This quantitative study employed an analytical observational design with a cross-sectional approach. The study involved 30 first-trimester pregnant women selected using total sampling. Data were collected through structured questionnaires and analyzed using descriptive statistics and the Chi-Square test with a significance level of α = 0.05. Most respondents were aged 20–25 years (53.3%), had senior high school education (63.3%), were housewives (53.3%), and were equally distributed between primigravida and multigravida (50.0% each). Good implementation of midwifery care and adequate implementation each accounted for 36.7%, while poor implementation accounted for 26.7%. Half of the respondents experienced moderate stress (50.0%), followed by high stress (36.7%), and low stress (10.0%). Most respondents were not at risk of preterm birth (73.3%). Chi-Square analysis demonstrated a significant relationship between the implementation of midwifery care and maternal stress levels (p = 0.000). The implementation of quality midwifery care during the first trimester is significantly associated with maternal stress levels. Strengthening comprehensive antenatal care may reduce maternal stress and contribute to the prevention of preterm birth.