A stereological method for estimating the feto-maternal exchange surface area in the bovine placentome at 135 days gestation

The feto-maternal relationships within the bovine placentome at 135 days gestation were investigated using unbiased stereology. This provides an estimate of the feto-maternal interface without physically separating these. The functional surface area, the volume of the fetal and maternal components, volumetric tissue shrinkage due to processing, and the feto-maternal surface amplification factor were estimated and quantified in standard units. In this healthy bovine pregnancy there were 105 placentomes with a total volume of 900 ml. The volumetric tissue shrinkage was 24% and the maternal: fetal tissue ratio overall was 0.92. The total feto-maternal exchange surface area was 18.5 m 2 with a surface amplification factor of 108.1. Analysis of the coefficient of error from counting different numbers of points within the reference area suggested that 50% and 75% fewer points could be counted to achieve the result obtained by counting approximately 6000 points used in this study.