ObjectiveTo systematically review the associations of maternal diabetes mellitus with cleft lip and palate in offspring. MethodsThe PubMed, EMbase, Cochrane Library, Web of Science, CNKI, VIP and WanFang Data databases were electronically searched to collect the observational studies on the association of maternal diabetes mellitus with cleft lip and palate in offspring from inception to June, 2024. Two reviewers independently screened literature, extracted data and assessed the risk of bias of the included studies. Meta-analysis was then performed by using Stata 17.0 and RevMan 5.4 software. ResultsA total of 34 studies involving 2 556 911 participants were included. The results of meta-analysis showed that maternal pregestational diabetes mellitus was associated with an increased risk of cleft lip and palate in offspring (OR=1.91, 95%CI 1.59 to 2.30, P<0.01). Maternal type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) were also associated with an increased risk of cleft lip and palate in offspring(T1DM: OR=2.28, 95%CI 1.65 to 2.30, P<0.01; T2DM: OR=1.87, 95%CI 1.10 to 3.19, P<0.01). There was no correlation between maternal gestational diabetes mellitus and cleft lip and palate in offspring. ConclusionCurrent evidence shows that maternal pregestational diabetes mellitus was associated with an increased incidence of cleft lip and palate in offspring. Due to the limited quality and quantity of the included studies, more high quality studies are needed to verify the above conclusion.