To investigate possible causes of abortion (and intrauterine foetal death) we reviewed clinical and morphological data of foetuses and placentas morphologically from 830 spontaneous abortions seen during a 12 years period (1978-1989) at the Institute of Pathology, University of Leipzig, and the Pathological Institute of Hoyerswerda. Our review showed that definite and possible causes of foetal death and abortion could be classified as placental, foetal maternal, and clinical. Placental changes, which included infection of the foetal membranes, disturbances of the uteroplacental circulation (abruptio placentae with bleeding) and placental dysmaturity, were the most important causes and accounted for 73.8% of the cases. Foetal causes mainly comprised multiple twin pregnancies and foetal malformations. In 20 cases (2.4%) we found malformations as a cause of foetal death and consecutive abortion. Overall, malformations were found in 7.5% of the cases examined. Maternal and obstetric complications of pregnancy were less frequent. In 16.5% of our cases, the cause of the abortion or intrauterine death remained obscure. However, since 1989, genetic analysis and prenatal diagnostic procedures have improved, bringing a greater knowledge on the spectrum and aetiology of possible developmental disorders in the foetus. This should reduce the number of unexplained abortions.