MR Dictionary

Dynastic effects are the potential for MR causal estimates to be confounded by characteristics that are transmitted across generations. For example, an MR study of the effect of height on coronary heart disease might be biased by a dynastic effect through a confounding path linking genetic instruments for height to coronary heart disease via the correlation between own and mother’s height genes and the possibility that maternal height influences fetal growth and development in utero, which influences future offspring (own) heart disease. 

It is difficult to detect the magnitude of any bias resulting from this. It is less likely to occur in MR studies of ‘own’ risk factors (as opposed to  intrauterine exposures from maternal pregnancy risk factors), that are not ‘visible’ and, hence, not likely copied from parents by offspring. Triangulation of MR findings with those from other methods that have different and unrelated potential causes of bias can help improve confidence about whether MR results are markedly biased by these effects. 

References

Other terms in 'Sources of bias and limitations in MR':