Sunday, 6 December 2009

Placentogram


When I was working on Placenta with a PhD student (Charlie Orton) at the University of Liverpool. We wanted to represent for a cohort of cases all the information relating to a placenta from the mother (age, smoking or not, number of previous pregnancies), via the baby (sex, Apgar score, weight) to the macroscopic condition of the placenta (weight, size, condition) to the microstructure of the various components of the placanta in three layers (e.g. total surface area of terminal villi etc). The resulting display was based on finest Edward Tufte principles and we were very proud of it. I called it the Placentogram. The diagram therefore showed data on over 6 orders of magnitude in length (metres to microns) and allowed clinicians the chance to relate the clinical data they were used to seeing (e.g. Apgar score) with microstructural information that they were unused to.


Here is a real example. This plot shows the data from 14 births each individual birth is a column top to bottom. This was a subset of the Normal Birthweight - Non-smoking group. At the top is the mass of the baby in grams, then gender (I used international symbols for male and female), parity (how many confinements the mother has had at this birth)and the centile for the babys weight. The mass plot shows the max and min to the extreme right with mean and +/- 2 Standard errors. Next down is placental mass in grams, again with with mean and +/- 2 Standard errors, at right. I ordered these in increasing mass as the placenta was the key structure in the study. 

Below this is two boxes of data relating to the microstructure of the fetal capillary bed within the placenta. The terminal villi are anatomically defined and are the finest villi. The volume refers to total volume of terminal villi within the placenta and the three grey boxes indicate how this is distibuted in three equal volume tertiles. The maternal side is uppermost and fetal side lower. The dark grey indicates most volume of terminal villi in that tertile, mid grey the middle rank and white the lowest. The next box refres to the surface area of the terminal villi using same coding as the volume box. 

Comments: I produced this in MS Powerpoint! Which was a drag but the output doesn't look bad I think. The data moves from baby/mother at top to placenta below. Each parameter can be compared across the cohort and each individual up and down. The microstructural data is obtained with rigorous quantitative techniques called stereology (REF: Unbiased Stereology; Three-Dimensional Measurement in Microscopy by C.V. Howard & M.G. Reed Bios 2005). As you might expect there is a higher volume of the terminal villi nearer the maternal side of the placenta and likewise with the surface. The plot is worth looking at closely as one can make connections and comparisons in different ways. I am interested in the microstructural data first but a clinician may well come at it top down. 

Source: All data from an unpublished but excellent PhD thesis by my friend and colleague Dr Charlotte (Charlie) Orton - Stereological analysis of human placental microstructures from pregnancies complicated with intrauterine growth retardation and maternal cigarette smoking: a prospective case-controlled study. University of Liverpool 2002. Charlie looked in detail at about 150 placentas in total. 


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