Pre-eclampsia: Is the immune maladaptation hypothesis still standing? An epidemiological update.

Despite much research, and clear improvement in our understanding of risk factors and pathogenetic mechanisms, the exact etiology of pre-eclampsia remains unknown. The immune maladaptation hypothesis has been challenged recently by several large epidemiological studies. One of the explanations for contradictory findings might be that the type of pre-eclampsia seen by obstetricians in developed countries mostly involves 30 and more years old, mildly obese pregnant women having near-term pre-eclampsia. It could be that this type of pre-eclampsia is primarily related to pre-existing maternal constitutional factors. This type of pre-eclampsia might be the dominant type of pre-eclampsia in the large Scandinavian and USA studies. In contrast, the epidemiology of pre-eclampsia in young women (age 15-25), so commonly seen in developing countries and certain lower socio-economic groups in developed countries, appears more in line with the immune maladaptation hypothesis. The aim here is to provide an updated review on studies supporting or challenging the immune maladaptation hypothesis.