Placentitis--Placental and Post-Mortem Examination

Donald Schlafer, DVM, MS, PhD, Dipl. ACVP, ACVIM, ACT, professor of comparative obstetrical and gynecological pathology in the college of veterinary medicine at Cornell University, presented a detailed account of how a veterinarian might carry out a post-mortem examination of the equine placenta, fetus, and neonate at the 50th annual American Association of Equine Practitioners (AAEP) Convention in Denver, Colo., Dec. 4-8, 2004. Performance of a thorough placental examination, he said, requires a basic understanding of placental anatomy and some familiarity with the gross features found in a normal placenta.

"Two essentials of a thorough gross placental examination," he said, "are (1) that one can distinguish normal features and common artifacts from lesions that may have diagnostic significance, and (2) that one knows how to collect an appropriate set of samples for submission to a diagnostic laboratory."

Step number one when examining a placenta, Schlafer said, is simplified by first finding the cord and carefully unfolding and flattening the three 'arms' of the Y-shaped chorioallantoic membrane (the outer membrane in the placenta). One of the first concerns, he emphasized, is to check for completeness because retention of pieces of the tips of the horns is relatively common and can have serious consequences if they remain inside the mare's uterus.

The umbilical cord also should be examined, he said, to determine if cord torsion has occurred, something that is not uncommon in the horse. Undue twisting of the cord can obstruct blood and urine flow.

When examining a placenta, he said, one of the most important areas is the cervical star, where the foal normally erupts through the placental membranes.

"The chorioallantoic cervical star deserves special attention because it is that part of the placenta that is physically against the inner side of the cervix. Because ascending infections through the cervix are common in the pregnant mare, the cervical star area must be carefully examined and routinely sampled. During normal delivery, the foal ruptures through the amnion and then through the chorioallantois at the cervical star which is in direct apposition to the cervix. If the placenta is prematurely separated from the endometrium, the fetus can rupture the chorioallantois in an area that is not the cervical star. This finding and the presence of a markedly congested chorioallantoic membrane in the distal body near the star are important diagnostic features of premature placental separation."

Schlafer then went into detail on what samples should be taken for laboratory analysis and approaches involved in doing a foal necropsy.

He also provided a suggested pathology report form for veterinary use when dealing with an aborted foal.

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

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