BACKGROUND: Clinical and preclinical evidence indicate that in utero maternal asthma exposure increases progeny asthma risk. Whether maternal asthma also increases the risks of progeny allergy is unclear. OBJECTIVES: To synthesise the available evidence on the relationship between in utero exposure to maternal asthma and postnatal asthma, wheezing and allergic diseases (Prospero: CRD42020201538). SEARCH STRATEGY: We systematically searched MEDLINE [PubMed], Embase [Ovid], Web of Science, Informit Health, the Cochrane Library, CINAHL [EBSCOhost], MedNar [Deep Web Technologies], ProQuest Theses and Dissertations, Scopus [Elsevier] and Trove, to the end of 2023. SELECTION CRITERIA: Studies reporting asthma, wheeze and/or allergic disease in progeny of women with and without asthma or with asthma classified by control, exacerbation or severity. DATA COLLECTION AND ANALYSIS: Double screening, selection, data extraction and quality assessment were performed, using Joanna Briggs Institute (JBI) scoring. MAIN RESULTS: Of 134 non-overlapping studies, 127 were included in ≥1 meta-analysis. Maternal asthma ever was associated with greater risks of asthma (65 studies, risk ratio [95% confidence interval] 1.76 [1.57-1.96]), wheeze (35 studies, 1.59 [1.52-1.66]), food allergy (5 studies, 1.32 [1.23-1.40]), allergic rhinitis (7 studies, 1.18 [1.06-1.31]) and allergic dermatitis (14 studies, 1.17 [1.11-1.23]) ever in progeny. Asthma during the pregnancy, more severe, and uncontrolled maternal asthma were each associated with greater risks of progeny asthma. CONCLUSIONS: Children of mothers with asthma are at increased risk for the development of allergic diseases. Whether improved maternal asthma control reduces risks of child allergy as well as asthma requires further investigation.