In a second study, the Cardiff IVF sample was used to examine the association between maternal smoking during pregnancy and child antisocial behavior (Rice et al., 2009). The inclusion of the genetically unrelated rearing mothers (embryo donation or egg donation) provides a naturalistic experiment to help disentangle genetic from prenatal associations. Analyses indicated that the association between prenatal smoking and child antisocial behavior was present in genetically related mother-child dyads, but was absent in genetically unrelated mother-child dyads. This suggests that genetic factors play a role in the association between maternal smoking during pregnancy and child antisocial behavior, rather than there being a direct causal pathway from prenatal smoking to child antisocial behavior. Conversely, this study found that prenatal smoking reduced child birth weight in both unrelated and related children, consistent with effects arising from prenatal mechanisms independent of the relation between the maternal and child genomes. This design and pattern of findings can thus point prevention researchers in the direction of specific postnatal and/or prenatal intervention targets in ways that would not be possible without this type of design.
