Little attention has been paid to the pathologic features of the umbilical cord, which might fatally damage the fetus. We determined the association of hypercoiling (more than 1 coil per 5 cm) and thinning with consecutive constriction of the umbilical vessels (thin cord syndrome; TCS) and intrauterine fetal death (IUFD). Three hundred and three cases of consecutive fetal autopsies over a 5-year period, including spontaneous and induced abortions of the 2nd trimester of pregnancy, were examined using a standardized protocol. The mean maternal age was 28.5 years and the mean gestational age was 19.1 weeks (range: 12.6 to 24.5 weeks). Thirty-six percent of all cases were induced abortions because of congenital malformations, and 8.9% resulted from legal abortions, as regulated by German law. One hundred sixty-seven cases (55.1%) were spontaneous abortion specimens. The leading cause for IUFD in the spontaneous abortion group was an amnion infection (34.7%), followed by abruptio placentae (15.6%). In 25.1% of cases, placental dysmaturity with consecutive placental insufficiency was responsible for IUFD. Pathologies of the umbilical cord as the cause of IUFD were seen in 10.2% of the cases. Most of these cases (15/17) involved TCS. In 14.4% of all spontaneous abortion specimens the cause of IUFD could not be determined by autopsy. There was an apparent difference in the frequency of TCS in the spontaneous abortion group (15/167 = 9%) compared to the nonspontaneous group (2/136 = 1.5%). A remarkably high percentage (17/303 = 5.6%) of all cases showed TCS. In cases of spontaneous abortions, TCS was causative for intrauterine death in 9% of cases (15/167). Careful pathologic examination of the umbilical cord is recommended to detect TCS and to reduce the cases with unexplained intrauterine death.