Small placentas were associated with pre-eclampsia, and more strongly with preterm than term pre-eclampsia. In term pre-eclampsia, the association with placenta weight was u-shaped, yielding higher proportions of both low and high placenta weight compared to pregnancies without pre-eclampsia.

The increase in the prevalence of pre-eclampsia and the difference between Akershus and the rest of Norway are not likely to be explained by changes in genetic material. Altered registration routines throughout Norway since 1998 may influence the observations, and better registration routines may contribute to the observed lower prevalence in Akershus. Changes in lifestyle factors most likely explain the overall increase in the prevalence of pre-eclampsia.

a possible type 1 immune response was identified both during preeclampsia and towards term. In pre-eclampsia a premature activation of leucocytes might be present.