Pre-eclampsia has been defined as a disease of first pregnancies. The association between primiparity and pre-eclampsia is so widely accepted that it is at the core of several pathophysiological theories. For example, it has been proposed that pre-eclampsia is the consequence of a maternal immune reaction against paternal antigens expressed in the placenta and that this reaction might result in defective trophoblast invasion and subsequent placental dysfunction.
The lower risk of pre-eclampsia among multiparous women has been attributed to desensitization after exposure to paternal antigens in the placenta during previous pregnancies. The lower risk has also been attributed to smoother trophoblastic invasion after modification of maternal spiral arteries during the first pregnancy.
- The risk of pre-eclampsia is higher in first pregnancies (4.1%) than in subsequent ones (1.7%) The lower overall risk of pre-eclampsia among parous women is not explained by fewer pregnancies among women who experienced pre-eclampsia in a previous gestation
- The risk of recurrence is around 15% for women who had pre-eclampsia in one previous pregnancy and around 30% when two consecutive previous pregnancies were affected
- Recurrence is higher for pre-eclampsia associated with the very preterm delivery
Source: Sonia Hernández-Díaz Risk of pre-eclampsia in first and subsequent pregnancies: prospective cohort study BMJ 2009;338:b2255