Introduction: Smoking during pregnancy poses severe public health risks, including preterm birth, low birth weight, and congenital anomalies. Despite ongoing public health efforts, the prevalence of smoking among pregnant women in the United Kingdom (UK) remains concerning. Methods: A mixed-methods systematic review was conducted, focusing on studies published between 2014 and 2024. The search strategy was designed to retrieve relevant studies from PubMed, CINAHL, Cochrane, and Medline databases, using a combination of keywords, Medical Subject Headings (MeSH), and Boolean operators (e.g., AND, OR). Eligibility criteria required studies to specifically examine factors influencing smoking cessation in pregnant women, including psychosocial, behavioural, and healthcare-related aspects. Only studies in English and conducted in the UK were included to ensure geographic relevance. Results: The review identified significant barriers to smoking cessation, including psychological dependence, financial strain, and a lack of social support. Conversely, facilitators included the motivation to protect infant health, supportive healthcare providers, and the use of digital interventions like MiQuit, which provided continuous motivational support. Conclusion: The findings highlight the need for multi-faceted, tailored interventions that address both psychological and socioeconomic challenges. Integrating mental health support, offering non-judgmental, personalized approaches, and embedding cessation programs into routine prenatal care are essential for improving smoking cessation outcomes among pregnant women.