Fetal postmortem weight loss in utero



Chard1 recently addressed the issue of weight loss in utero following fetal death at 24–32 weeks of gestation. He concluded that, although stillbirth weights were lower than live birth weights for gestation, many stillbirths may have a normal ‘true’ adjusted weight and would therefore be unlikely to be predicted by studies of fetal size alone. It is, as stated1, well recognised that stillbirth weights are lower than live birth weights at all gestations2. Furthermore, the in utero changes that occur postmortem are well reported and are due to a combination of the effects of maceration and tissue autolysis2, with resultant fetal tissue loss over a long period, as evidenced by the presence of a residual shrunken fetus at term in cases of twin pregnancies complicated by single intrauterine death in midtrimester. In order to account for at least some aspects of postmortem weight change, pathologists predominantly rely on organ weight ratios rather than actual body or organ weights to diagnose intrauterine growth restriction. Using organ weight data from live birth and stillbirth series2, organ weights are lower in stillbirths, but the brain/liver weight ratio, although marginally higher than for live births, remains within the normal range (3–4:1). Only when such a ratio is markedly abnormal (5–6:1) is the diagnosis of chronic intrauterine growth restriction due to uteroplacental insufficiency provided3, and in most of these cases, there will also be histological evidence of uteroplacental disease in the placenta. Using these criteria, only around 10% of stillbirths, most of which occur antepartum, are registered with intrauterine growth restriction as the likely cause of death3. Most cases of stillbirth therefore remain ‘unexplained’. These data, along with the conclusions of Chard1, further highlight the need for both detailed perinatal postmortem examination in all cases of stillbirth and the importance of adequate communication of the full clinical history and all relevant investigations between obstetrician and pathologist in order that improved understanding of the true aetiologies of stillbirth may be achieved.