Association between childhood asthma and history of assisted reproduction techniques: a systematic review and meta-analysis.

Genetic and environmental factors during early development may influence lung growth and impact lung function. We performed a meta-analysis of epidemiological studies examining the association between conception history of assisted reproduction techniques (ART) and childhood asthma. We searched PubMed and Embase up to November 2020 for relevant observational studies and synthesized data data under a fixed or random effects model as appropriate. Heterogeneity was assessed using the I2 metric. We identified 13 individual studies including 3,226,386 participants. We did not observe a statistically significant association between ART and physician-diagnosed asthma (n = 9, random OR 1.16; 95% CI 0.94-1.43; I2 61%). We observed a statistically significant association between ART and prescription of asthma medications (n = 6, fixed OR 1.27; 95% CI 1.23-1.32; I2 0%). Wheezing was also associated with ART (n = 4, fixed OR 1.71; 95% CI 1.08-2.72; I2 0%). When we combined studies using any asthma definition, a statistically significant association was observed (random OR 1.19; 95% CI 1.05-1.34; I2 80%).Conclusion: The available observational evidence suggests that the risk of asthma is higher among children born after ART. The mechanism and potential sources of bias behind this association are under scrutiny, and further work is needed to establish causality. What is Known: • "Positive" epidemiological signals for the association between assisted reproduction techniques and asthma stemming from large studies were not replicated by subsequent research. • Any available research synthesis effort so far bears no quantitative aspect. What is New: • The available observational evidence suggests that the risk of asthma is higher among children born after ART. • The mechanism and potential sources of bias behind this association are under scrutiny.