Incidence and relation to parity of pregnancy-induced hypertension in Iceland

A retrospective study was made to determine the incidence of pregnancy-induced hypertension (PIH, pre-eclampsia) in Iceland. One-fourth of all births in Iceland in 1985 were selected from the national birth registry files by random number allocation, a total of 904 women. Maternity records were found in 97.9% of the cases. The criteria used to define PIH were met in 17.4% of the women. There were 146 (16.5%) with mild PIH (blood pressure of greater than or equal to 140/90 mmHg with or without proteinuria after the 20th gestational week). Eight (0.9%) had severe PIH (blood pressure of greater than or equal to 160/110 mmHg with or without proteinuria after the 20th gestational week). Primigravid women formed one-third of the group and of these 20.9% had PIH compared with 15.4% of the parous women. The incidence in parous women was higher than usually reported.