What is adequate sampling of extraplacental membranes?: a randomized, prospective analysis

It is the generally accepted practice to submit 1 or 2 membrane rolls when examining placentas.

To determine whether obtaining additional sections would increase diagnostic yield and, if so, to what degree.

A membrane roll section was prospectively procured from each quadrant of its respective singleton placenta. These placentas were submitted for routine pathologic examination, the process of which was entirely separate from this study. All study sections were randomized and assigned new numbers, thereby blinding the pathologist to the placenta of origin. We evaluated the incidence of acute chorionitis/chorioamnionitis (AC/A) and atherosis when 1, 2, 3, or 4 slides were examined. The diagnostic yield from all possible combinations of single, pairs, and triplets of sections was tabulated. When an additional slide identified more extensive acute inflammation than what was demonstrated initially, the AC/A was upstaged.

With 1 section examined, 7 to 10 placentas had AC/A. With 2 sections, 10 to 15 placentas had AC/A; with 3 sections, 16 to 18 cases; and with 4 sections, 19 cases. Additional sections upstaged the AC/A diagnosis infrequently. A total of 4 of 53 placentas had atherosis, based on review of all 4 slides. One slide identified 1 to 3 cases of atherosis. With a second and third section, the yield increased to 2 to 4 and 3 to 4, respectively.

Review of a single membrane roll identified, at most, 53% of cases of AC/A and 50% of cases of atherosis. Additional sections increased the yield for both diagnoses in a roughly linear manner.