Background: First-time mothers often face unique challenges due to limited prior experience, making knowledge of postpartum changes essential for effective adaptation. Sociodemographic factors such as age, education, occupation, and marital status may influence baseline knowledge and readiness to learn which can inform the design of effective health education interventions. Objective: To determine the association between pre-intervention knowledge of postpartum changes and sociodemographic characteristics of first-time mothers. Methods: A quasi-experimental study was conducted among 204 first-time mothers in Zaria Metropolis, Nigeria, assigned to study (n = 64) and control (n = 64) groups. Baseline knowledge of postpartum changes was assessed using a validated 10-item questionnaire. Sociodemographic characteristics including age, education, marital status, ethnicity, religion, and occupation were collected. Associations were analyzed using Chi-square tests, with significance set at p < 0.05. Results: In the study group, no significant associations were observed between pre-intervention knowledge and any sociodemographic characteristics, including age (χ² = 6.445, p = 0.40), education (χ² = 3.307, p = 0.347), marital status (χ² = 0.632, p = 0.427), ethnicity (p = 0.977), religion (p = 0.594), or occupation (p = 0.437). Whereas, in the control group, age (χ² = 9.820, p = 0.007) and education level (χ² = 7.080, p = 0.002) were significantly associated with pre-intervention knowledge, with older mothers (25–29 years) and those with secondary or tertiary education demonstrating higher baseline knowledge. Other variables, including marital status, ethnicity, religion, and occupation, were not significantly related to knowledge. Conclusion: Baseline knowledge of postpartum changes among first-time mothers is generally independent of most sociodemographic characteristics, except for age and educational level in the control group. These findings suggest that interventions aimed at improving maternal knowledge should focus on younger mothers and those with lower educational attainment while remaining accessible to all first-time mothers. Recommendation: Maternal health education programs should be universally provided but tailored to address the needs of younger mothers and those with lower formal education to enhance postpartum knowledge and adaptation.