Table 5.

Variance explained by each variance source (95% confidence intervals)

Maternal phenotype	Additive genetics	Environment unique to one mother	Environment shared between sisters who are mothers	Spouse effect	Environment unique to each pregnancy
Maternal smoking during pregnancya	69% (67%, 70%)	3% (2%, 4%)	4% (3%, 5%)	16% (15%, 16%)	8% (8%, 9%)
Offspring phenotype	Additive genetics	Environment shared between siblings	Environment shared between cousins	Paternal effect	Unique individual environment
Birth weight	50% (47%, 53%)	16% (15%, 17%)	7% (7%, 8%)	0% (0%, 0%)	27% (26%, 28%)
Preterm birth	27% (19%, 35%)	24% (21%, 27%)	8% (6%, 9%)	0% (0%, 0%)	41% (37%, 46%)
Born small for gestational age	43% (34%, 52%)	16% (12%, 19%)	7% (6%, 9%)	0% (0%, 0%)	34% (29%, 38%)
Low academic achievement	86% (78%, 94%)	1% (−1%, 3%)	12% (11%, 14%)	0% (−1%, 1%)	1% (−4%, 5%)
General cognitive ability	33% (26%, 39%)	19% (10%, 29%)	0% (0%, 0%)	1% (−8%, 10%)	46% (43%, 50%)
Criminal convictions	39% (19%, 60%)	2% (−5%, 9%)	4% (1%, 7%)	0% (0%, 0%)	54% (43%, 66%)
Violent criminal convictions	63% (42%, 84%)	2% (−5%, 8%)	6% (2%, 11%)	0% (0%, 0%)	29% (16%, 42%)
Drug/alcohol misuse	35% (30%, 40%)	6% (4%, 8%)	3% (1%, 4%)	1% (1%, 2%)	56% (51%, 60%)

Note: Estimates are from univariate models. Wald-type confidence intervals, hence negative values may exist in intervals. Parameters were fitted using the non-squared, and, if applicable, non-standardized variance parameters, therefore standard errors are calculated using the delta method.

^aCalculated using the full 1983–2009 cohort.