Background: Obesity during pregnancy has a high incidence rate worldwide. At the same time, postpartum weight of pregnant obese patients can lead to a series of complications. This study aimed to examine the effectiveness of independent self-monitoring (SM) interventions during pregnancy and postpartum on reducing postpartum weight retention in women with obesity during pregnancy. Methods: A multicenter observational study was conducted, involving 448 participants diagnosed with obesity during pregnancy, from five medical organizations. Participants were divided into two groups: those with independent SM activities (SM; n = 201) and those without independent self-monitoring activities (no-SM, NSM; n = 247). Independent SM behaviors included dietary and weight measurements. Linear mixed-effects models with repeated measures, and multiple logistic regression models were employed to assess continuous and categorical weight outcomes, respectively. Results: Changes in body weight were observed from the prepregnancy period to the 12-month postpartum phase. An observable SM effect was evident, resulting in reduced weight retention in the SM group across various time intervals. Notably, at the 12-month postpartum mark, the SM effect retained a slight but significant impact, with the SM group maintaining 2.4 kg less weight compared to the NSM group (95% confidence interval (CI): –4.5 to –0.3). Furthermore, relative to NSM participants, the SM group exhibited a 2.5-fold increased likelihood (95% CI: 1.2–4.8) of experiencing no weight retention at 3 months postpartum compared to their prepregnancy weight. Additionally, SM was associated with a higher probability of vaginal delivery and a decreased likelihood of cesarean sections (p = 0.046). Importantly, no significant distinctions were observed in neonatal outcomes or among participants with varying gestational weight gain (GWG) levels (p = 0.144 and p = 0.064). Conclusion: Independent SM interventions, comprising dietary and weighting, are effective in limiting postpartum weight retention among women with obesity during pregnancy, and enhance delivery method. Healthcare professionals should consider incorporating independent SM strategies into prenatal and postnatal care programs, to support healthy weight management and reduce the risk of adverse pregnancy outcomes and long-term obesity development.