Organ weights in human fetuses after formalin fixation: standards by gestational age and body weight

This study provides new standards of fetal organ weights (brain, heart, liver, pancreas, spleen, lungs, kidneys, adrenals, thymus, and thyroid) and body dimensions (crown-heel and crown-rump lengths, head circumference, and foot length). Subjects came from a large dataset including more than 4,000 fetuses autopsied in fetopathology units of pediatric hospitals in Paris between 1986 and 2001. From this dataset, 673 subjects were carefully selected by exclusion of multiple pregnancies, macerated and malformed fetuses, subjects with abnormal karyotypes, and those with severe infections. Fetal age ranged from 9 to 42 gestational weeks, with a very large sample of fetuses in the first half of gestation. Each organ was weighed after fixation in formalin. The standards were computed in relation to age and body weight. The mathematical models used to fit the percentile growth curves were carefully selected for each organ or dimension. This study, based on reliable methodology, affords a whole set of accurate growth standards useful for pathologists.