Histologic Estimation of Intrauterine Retention Time after Fetal Death

The fetus undergoes postmortem changes after death in utero due to autolysis. Several reports have suggested that the autolysis may provide a method for determining the intrauterine retention time (IURT).Among them, the Genest’s study has presented the loss of nuclear basophilia as a most reliable histologic indicator. According to the Genest’s criteria, 10 histologic features based on loss of nuclear basophilia were found to have sufficient specificity, sensitivity, and positive predictive values. Specificity and sensitivity were assessed by classifying death to delivery time into 13 time windows, and 86% of the fetuses assayed could be assorted into one of seven time windows. But applying these criteria, three types of practical limitations are revealed. The first is the internal problem of Genest’s methods. Time windows for IURT are arbitrary. For example, a true death-todelivery time of 23 h 59 min would be classified into the ‘≥ 4h and ≤ 24h’ time window, whereas a deathto-delivery time of 24 h 1 min would be classified into the ‘≥ 24h’ time window. The second is the pathologic conditions that accelerate or decelerate the autolysis rate should be excluded in advance and more detailed. The third is the assessment of 10 histologic features to keep the Genest’s criteria is still affected by the kappa value for inter or intra-observer