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Introduction: Low birth weight is associated with reduced FEV1 in adulthood, which is often used to support the claim that low birth weight is associated with airflow obstruction. However, low FEV1 can indicate either airflow obstruction (low FEV1/FVC) or restriction (low FVC). Here, we report a systematic review and meta-analysis on the effect of birth weight on FEV1/FVC and FVC in adulthood, hereby attempting to disentangle early life effects on obstruction vs restriction. Methods: Eligible studies were published before January 27, 2015, of any design, and reporting associations of birth weight, weight at one year and weight gain in the first year of life with FVC and FEV1/FVC in adults. The authors searched EMBASE, MEDLINE and Web of Science for studies, screened titles and abstracts and extracted data in duplicate. Data were synthesized using a random effects inverse-variance weighted meta-analysis, and between-study heterogeneity was evaluated using I 2 . Results: After de-duplication, the searches identified 718 records, of which 18 were eligible for the review and 12 had sufficient data for the meta-analysis. We found that one kg increase in birth weight was associated with 59.4mL increase in FVC (95%CI: 43.3 to 75.5mL; I 2 :0), with no evidence of association for FEV1/FVC. Conclusion: Birth weight showed a positive association with FVC highly consistent across studies, while there is no epidemiological evidence to support an association between birth weight and FEV1/FVC.