Figure 2.

Two-level mediation model within the maternal line. The two ellipses represent: (i) the level 2 unit (mother; the presence of arrows indicates the random intercept terms at level 2); and (ii) the cluster variable (centre; the absence of arrows indicates that cluster-robust standard errors were computed in order to take the correlation among mothers within centres into account). *The ‘unknown’ category is not shown. ^†Smoking during other periods (or unknown smoking period).