Background Antenatal care (ANC) is a crucial component of maternal and child health, yet disparities in utilization persist globally. This study aimed to assess the patterns of ANC service utilization and adherence among pregnant women attending primary healthcare centers (PHCCs) in Al-Ahsa, Saudi Arabia. Methodology A quantitative, cross-sectional study was conducted among 277 women attending PHCCs in Al-Ahsa. Data were collected through structured questionnaires, assessing demographic characteristics, ANC follow-up patterns, structural and personal barriers, and mental health conditions using the Depression, Anxiety, and Stress Scale. Results Significant regional variations in ANC follow-up patterns were observed, with higher proportions of pregnant women attending ANC in the Middle and Eastern regions. Prominent structural barriers included transportation challenges (structural barrier 3, 61.0%) and limited service availability (structural barrier 6, 56.0%), while personal barriers encompassed transportation problems (personal barrier 6, 36.8%) and forgetfulness regarding appointments (personal barrier 4, 19.9%). Mental health assessments revealed predominantly normal levels of depression, anxiety, and stress, with some regional variations in distress levels. Conclusions The study highlights regional disparities in ANC service utilization and adherence, influenced by structural barriers, personal barriers, and mental health conditions. Tailored interventions addressing these barriers, improving access to care, and providing targeted support are crucial for enhancing ANC service utilization and promoting maternal and child health in Al-Ahsa.