BackgroundThis study aimed to evaluate spatial changes in dental arches resulting from premature loss of first primary molars and assess the necessity of a space maintainer.MethodsWe searched the electronic databases PubMed, Cochrane Library, ClinicalTrials, and EMBASE. Split-mouth studies involving unilateral premature loss of a primary first molar were included. Quality assessment of selected studies made use of the ROBINS-I tool. Mean space differences were calculated for the D + E and D spaces, arch width, arch length, arch perimeter.ResultsOf the 329 studies considered, 11 split-mouth studies were selected, including 246 cases in the maxilla and 217 in the mandible from 477 individuals aged 5–10 years. Over the medium-term follow-up period (6–24 months), space loss was 0.65 mm in the maxillary D + E (MD 0.65, 95% CI 0.15–1.16, P = 0.01), 1.24 mm in the mandibular D + E (MD 1.24, 95% CI 0.60–1.89, P < 0.01), and 1.47 mm in the mandibular D (MD 1.47, 95% CI 0.66–2.28, P < 0.01). There was no significant change in arch width, length, or arch perimeter between the initial and follow-up examinations (P > 0.05).ConclusionsAfter premature loss of first primary molars, space can be lost, but the amount of loss would not affect arch width, length, or arch perimeter over the 6–24 months follow-up period.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12903-023-03111-x.