Aim: To investigate the impact of oral health care before conception and during mid-pregnancy in preventing gingivitis during pregnancy. Methods: Systematic evaluation and meta-analysis were conducted. Findings: Among the 14 trials, 5 were classified as having robust research methodologies, while the others were deemed to have lower methodological quality. Interestingly, the outcomes of trials with high and low methodological quality diverged significantly. High-quality trials suggested that pre-conception and mid-pregnancy interventions effectively reduced gingivitis, whereas the opposite was observed in low-quality trials. Furthermore, high-quality studies indicated that these interventions did not have a significant influence on pre-term birth rates (Odds Ratio: 1.15, 95% Confidence Interval: 0.95 – 1.40, p = 0.15) or the likelihood of low birth weight (Odds Ratio: 1.07, 95% Confidence Interval: 0.85 – 1.36, p = 0.55). Conclusion: Maintaining oral hygiene and implementing root planning and scaling are essential components of pre-conception and mid-pregnancy oral healthcare practices that effectively prevent gingivitis. Dental assessments during these critical periods yield positive results for the prevention of gingivitis. Importantly, these measures do not affect the occurrence of pre-term birth or low birth weight.