Although prostacyclin (PGI2) production in the umbilical artery is known to be reduced in pregnancy-induced hypertension (PIH), little information is available about its production in maternal vascular tissues. We measured 6-keto-prostaglandin F 1 alpha generation in the umbilical and omentum arteries of 24 Andean women divided into three groups: 1) 8 normal pregnant women, 2) 8 cases with clinical evidence of severe PIH, and 3) 8 normotensive non-pregnant women. The normal pregnant group (232 +/- 172 pg mg-1 2h-1) and the non-pregnant control group (237 +/- 146 pg mg-1 2h-1) showed similar PGI2 production in the omentum arteries, whereas the PIH group showed lower PGI2 generation (P less than 0.05) than the normal patients both in the umbilical (697 +/- 377 vs 1528 +/- 291 pg mg-1 2h-1) and omentum (132 +/- 73 vs 232 +/- 172 pg mg-1 2h-1) arteries. PGI2 production was 6.8 times lower in the omentum arteries than in the umbilical arteries. The data confirm and extend the view of the occurrence of reduced PGI2 production in the maternal-fetal vascular tissues of women with severe PIH.