Genetic and familial predisposition to eclampsia and pre-eclampsia in a defined population.
 Familial predisposition and patterns of genetic inheritance of eclampsia and pre-eclampsia were investigated through three or four generations in 94 families from the homogenous island population of Iceland.
 The families descended from index women delivered in the years 1931-47 and who had either eclampsia (n = 38) or severe pre-eclampsia (n = 69).
 Inheritance was followed both through sons and daughters.
 The prevalence of pre-eclampsia and eclampsia in daughters was significantly higher (23%) than that in daughters-in-law (10%).
 No difference was noted in the prevalence of these diseases by whether the daughter was born of an eclamptic or pre-eclamptic mother or whether she was a first or later born daughter.
 There was a non-significantly higher occurrence of pre-eclampsia among grand-daughters than in grand-daughters-in-law.
 No difference was seen by whether grand-daughters descended through sons or daughters.
 With increasing numbers of affected daughters or grand-daughters the probability rose of finding more affected women in a family.
 Hypotheses of single recessive and dominant gene inheritance were compared and maximum likelihood estimates for gene frequency obtained.
 For a single recessive gene model this was 0.31 reflecting a population prevalence of 9.6%, whereas a dominant model with incomplete penetrance gave 0.14 at 48% gene penetrance, corresponding to a population prevalence of 0.9% homozygous expression of severe disease and 11% heterozygous expression of milder disease.
 Either genetic model could fit the data.
