The diagnosis of lethal fetal malformation prenatally has profound implications for the pregnancy, the expectant couple and the medical care provided. The aim of this study was to investigate these implications and the medical factors pertaining to prenatal diagnosis of lethal fetal abnormality in current obstetric practice in Ireland. Data was collected prospectively from all cases of lethal fetal malformation diagnosed at the Fetal Medicine Unit, University College Hospital Galway from December 1997 to June 1998 inclusive. Diagnosis was made on the basis of ultrasound findings and invasive procedures (amniocentesis and chorionic villus sampling). Thirteen cases of lethal fetal abnormality were diagnosed: Edward's syndrome, Patau's syndrome, bilateral multicystic renal dysplasia, Potters sequence, hypoplastic left heart, anencephaly with craniorrhachischisis, lethal osteogenesis imperfecta and non-immune hydrops. Intrauterine death occurred in four cases. Four women had preterm complications e.g. preterm premature rupture of membranes, preterm labour, placental abruption, coagulopathy and severe pre-eclampsia. Three pregnancies progressed to term, two of which had a vaginal delivery and one had an elective caesarean section for malpresentation, all of which were early neonatal deaths. Three women chose to travel abroad in order to obtain a termination of pregnancy. Obstetric and neonatal dilemmas in management of lethal fetal malformation are discussed.