Superimposed preeclampsia refers to women with chronic arterial hypertension (primary or secondary) who develop preeclampsia (PE). Because hypertension affects 5-15 % of pregnancies, it is itself a matter of concern. However, this concern should be permanent, given the increased risk of the hypertension worsening and, particularly, the appearance of superimposed PE. The search for factors that underlie or promote the development of this disorder has been the subject of intense research. However, despite the wealth of knowledge, the cause or causes remain to be determined.