Maternal age at delivery and risk of allergy and asthma in the offspring: a systematic review and meta-analysis protocol

Introduction While several perinatal factors have been linked to the risk of developing asthma and allergy in childhood, the role of maternal age at delivery remains uncertain. Some studies suggest that young maternal age at delivery may increase the risk, while other studies suggested a reduced risk. To provide a clearer appreciation of the underlying evidence, we plan to undertake a systematic review to synthesise previous studies that have investigated the association between maternal age at delivery and the risk of asthma and allergy in the offspring. Methods and analysis We will search PubMed, EMBASE, ISI Web of Science, Scopus and Google Scholar to identify relevant studies on the topic published in the databases from inception until October 2020. We will search databases of proceedings of international conferences, contact authors who have published on the topic and search the reference lists of the included studies in order to identify additional studies. Two investigators will independently screen the identified studies, perform data extraction and examine the risk of bias in the studies; a third investigator will arbitrate throughout these processes. We will use the Effective Public Health Practice Project tool for assessment of the risk of bias in included studies. We will perform random-effects meta-analysis to combine effect estimates from included studies judged to be homogeneous. Ethics and dissemination Only data from the published literature will be included in this study, therefore no ethics approval is required. Our findings will be published in a peer-reviewed journal. Protocol registration The protocol has been submitted for registration on PROSPERO, University of York, and Centre for Review and Dissemination, now awaiting the assignment of a registration number.