Two women without a specific risk had fetuses with multiple malformations diagnosed by ultrasound; extensive biochemical investigations on fetal blood revealed clues which would have allowed the correct diagnosis of a genetic condition: Pallister-Killian syndrome in one with increased fetal LDH, and Smith-Lemli-Opitz type II syndrome in the other with low fetal cholesterolaemia. When compared with chorionic villus sampling and amniocentesis, rapid karyotyping in women with multiple fetal malformations by fetal blood sampling allows the collection of additional data which may lead to the diagnosis of specific genetic syndromes.