PLACENTA CIRCUMVALLATA Its Aetiology and Clinical Significance

BY

JOHN H. M. PINKERTON, M.D., M.R.C.O.G. From the Department of Obstetrics and Gynaecology, University College of the West Indies

ONE of the commonest and most striking aberrations of gross placental structure is the peripheral ring formed by a whitish circumfer- ential area which is free of superficial blood vessels and which may or may not completely encircle the placenta. It was found in 25 per cent of the placentas of 2,019 consecutive deliveries, including 154 abortions, in the University College Hospital of the West Indies.

There are two types; placenta marginata, in which the ring is only slightly, if at all, raised above the rest of the placental surface and is not undermined and placenta circumvallata in which the ring is definitely raised and is undermined to a greater or lesser extent so that a recess is formed under it (Fig. 1). Placenta marginata is much commoner, occurring in 22.5 per cent of all the cases, while placenta circumvallata accounts for only 2.5 per cent. Either type of ring may be complete or incomplete, that is to say, the ring may or may not completely encircle the periphery of the placenta. In our material, one-fifth of the marginate placentas were

complete, while four-fifths were incomplete; of the circumvallate placentas one-third were complete and two-thirds incomplete.

INCIDENCE OF THE CIRCUMVALLATE FORM This communication is concerned largely with

the circumvallate placentas of which 50 occurred in the series-an incidence of 2.5 per cent. The earlier writers, cited by Williams (1927), give a very high incidence of from 7.6 to 21.3 per cent. Williams himself, however, discovered the condition in only 2 per cent of his cases, while Hobbs and Price (1940) and Hunt, Mussey and Faber (1947) found 0.7 per cent and 0.5 per cent respectively. The high incidence given by earlier European workers was probably due to the inclusion of many cases of placenta marginata. On the other hand, an apparently low incidence of the condition will occur if only the more marked types are recorded. This may explain the discrepancy between the incidence given by Hobbs and Hunt and their co-workers, and that found in the present series (Table I).

TABLE I Incidence and Clinical Significance of Placenta Circumvallata as Recorded by Various Workers

(Percentages in brackets)

Number ofcases . . . . . . Incidence . . . . . . . . Abortions . . . . . . . . Bleeding during pregnancy . . Hydiorrhoea . . . . . . Premature rupture of membranes Premature births . . . . . . Foetal survival rate . . . . Retained membranes . . . . Manual removal of placenta . . Post-partum haemorrhage of 560 ml.

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . . or more

150 (0.7)

33 (22) 33 (22) 4 (2.6)

23 (16) 101 (67)

-

47 (0.5) 8 (17)

26 (55) 7 (15)

15 (32) 10 (21) 36 (74)

49 - -

19 (28) -

3 P1. 743

I44 AETIOLOGY

The study of the histological structure of these rings is complicated by the fact that frequently they are composed of dense, white tissue in which little or no detailed structure is discernible. Many theories of their aetiology were enunciated by European authors of the latter part of the last century, who evinced great interest in both the aetiology and the clinical significance of the condition.

Williams (1927), in the first paper written in English on the subject, summarized ten theories which had been propounded between 1885 and 1909. His own views have influenced nearly all subsequent writers, and, as far as the histology and aetiology of the condition are concerned, are still largely accepted. He postulated that the chorion frolidosum, by reason of some defect in ovum or decidua, became too small to support the demands of the growing ovum. Compen- sation was made for this by a lateral growth of villi into the adjacent decidua Vera which was thus split into a basal and a superficial layer; the former was continuous with the decidua basalis, but the latter formed a layer over the peripheral aspect of the placenta which lay outside the chorionic plate. As the foetus and its sac grew larger, the membranes became pressed against this decidua, and loosely attached to it, this area constituting that part of the surface of the placenta which lies outside the ring (Fig. 2).

We have found this decidua splitting theory unsatisfactory in three significant respects. Firstly, it fails to explain the most striking feature of the circumvallate placenta, namely, the undermined appearance of the ring (Fig. 1). Splitting of the decidua Vera adjacent to the placenta could only produce a flat peripheral ring with, at most, a slightly raised unfolded edge.

Secondly, we have been unable to demonstrate that “the ring is composed of folded foetal membranes” (Williams, 1927). In our material, the ring is composed of flattened, usually fibrotic, but quite definitely recognizable placental tissue covered on the foetal side by chorion and amnion and continuous with the rest of the placenta peripherally (Figs. 3 and 4).

Lastly, the decidua-splitting theory as stated by Williams ignores the placenta marginata as

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“having nothing in common with the condition under discussion”. We have repeatedly noted the circumvallate type of ring merging into the marginate type (Fig. 6) ; and we believe that they are both the result of bleeding at the edge of the placenta early in pregnancy. Bartholomew and his colleagues (1953) have pointed out that “when erosive action of chorionic tissue on decidual arterioles permits free pressurized flow of blood upwards through the intervillous spaces to the chorionic plate, thence outward in all directions beneath the chorionic .plate to the periphery of the placenta, the flow meets resistance at the junction of the decidua reflexa and Vera. Apparently, at this point, the decidua may be unable to contain the pressure of the maternal blood stream and a break-through occurs.” If this should happen the blood may pass in any of three directions. It may pass to the exterior between the chorion and the uterine wall. It may invade the chorionic plate, and, if the pregnancy continues, this will result in the appearance of a marginate placenta with its peripheral flattened ring of putty-like material derived from the fibrin and separating the membranes from the underlying placenta. Or the blood may strip up the placenta from the decidua basalis; if it does so to a marked degree, death of the foetus and abortion will be the result. If only the edge of the placenta is separated, it will curl up upon itself, and later, as the amnion and chorion are folded more firmly against it by the enlarging foetal sac, the curled up edge of the placenta will be flattened out to form the typical undermined ring of the circumvallate placenta (Fig. 5). The chorion will remain attached to the original edge of the chorionic plate and will therefore pass over the outer aspect of the definitive placenta to which it will be but weakly adherent, to a point some- where near the inner margin of the ring (Fig. 5).

In this manner we can account for the gross anatomical appearances of the circumvallate placenta, namely, the undermined and raised ring and the absence of superficial blood vessels outside it: for the microscopic appear- ances, namely, the chorion overlying but not firmly attached to the periphery of the placenta and the presence of placental tissue in the substance of the ring. The association of the

FIG. 1 Placenta Circumvallata. Note the marked undermining of the ring which

is raised well above the placental surface.

FIG. 2 Part of an illustration from Whitridge Williams’s paper demonstrating the decidua splitting theory. Ncte that there is no placental tissue shown in the

fold but only decidua Vera. Contrast with Figpres 3 and 5 .

J.H.M.P. [744]

FIG. 3 Photomicrograph of' a circumvallate fold. Note the placental tissue (P) in the substance of the fold. Most of the villi are embedded in hyaline mat- erial but are still recognizable. There is no decidual tissue in the centre of

the fold. x 12.

FIG. 4 Higher power photomicrograph of the same fold as in Figure 3 showing

placental chorionic villi (V) embedded in hyaline tissue (H). x 150.

J.H.M.P.

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PLACENTA CIRCUMVALLATA 745 CHORION

w l l h ATROPHIC VILLI

DECIDUA lombeddad In

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CAPSULARIS

3. FIG. 5

Diagram to illustrate the development of the circumvallate ring due to separation of the edge of the placenta.

two different types of placental ring, marginate and circumvallate, which may occur in the same placenta can also be accounted for in this way, since the bleeding at one point may be sufficient to separate the placenta from its decidual bed, while at an adjacent point it may merely infiltrate the chorionic plate leaving a fibrinous deposit in it.

CLINICAL SIGNIFICANCE OF THE CIRCUMVALLATE PLACENTA

There is little unanimity of opinion among writers on the subject as to the clinical signifi- cance of placenta circumvallata. The earlier European workers noted an increased tendency to abortion, intermittent haemorrhage (Kiistner, 1884; Schwab, 1895), and abnormalities of the third stage (Herff, 1896). Williams (1927) stated that in his experience placenta circumvallata was practically without clinical significance, and was

to be regarded merely as an interesting anatom- ical condition. But subsequent writers on the clinical aspects of the condition have emphasized its association with abortion, intermittent bleeding during pregnancy, ante-partum haemor- rhage and a foetal mortality rate as high as 33 per cent (Hobbs and Price, 1940); and with hydrorrhoea gravidarum and premature labour (Hunt et al., 1947). Pathologists are less emphatic about its clinical importance; thus Hellman (1947) comments : “usually the extra chorionic portion of the placenta is only 2-3 cm. in depth and so of little clinical significance.” He quotes Hertig as stating that ante-partum haemorrhage may be frequently associated with circumvallate placenta. Potter (1952) is of the opinion that, while the stillbirth rate is slightly higher with the most severe forms, the milder varieties are accompanied by no increase in mortality.

51A

746 Our own results are given in Table 11. From

this can be seen that in those pregnancies which went almost or completely to term, the foetus was at no apparent disadvantage on account of its abnormal placenta. The foetal mortality rate was not raised. As far as the mother was con- cerned, no increase in the incidence of premature rupture of the membranes or intermittent haemorrhage during pregnancy could be de- tected. There was, however, a marked increase in the incidence of post-partum haemorrhage in excess of 20 ounces (560 ml.); thus, among the 47 cases at or near term, 11 (or 23 per cent) lost 20 ounces or more as compared with 6 per cent among the total number of cases under review. This bleeding was not associated with undue delay in the third stage, its average duration being 20 minutes, and in only one instance was manual removal necessary, after the placenta had remained partially attached for 75 minutes.

DIAGNOSIS It is not possible to diagnose placenta circum-

vallata during pregnancy. Repeated small haemorrhages or discharges of liquor are suggestive but the diagnosis can only be con- firmed by inspection of the placenta after

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delivery. The bleeding which may occur during the latter half of pregnancy may be indis- tinguishable from inevitable haemorrhage, and the case must be treated as placenta praevia unless this can be excluded by radiological or other means. In one of our cases severe haemor- rhage occurred at the 28th week andecaesarean section was required to control it.

SUMMARY Fifty cases of circumvallate placenta occur-

ring in 2,019 pregnancies are discussed. The condition is believed to result from separation of the edge of the placenta early in pregnancy with subsequent curling up of the placental margin. In the antenatal period the condition may cause bleeding which is indistinguishable from that due to placenta praevia. In our series there was a high incidence of post-partum haemorrhage.

ACKNOWLEDGMENTS I am indebted to Professor D. B. Stewart

for much helpful criticism during the writing of this paper, and to the Editors of the American Journal of Obstetrics and Gynecology for permission to reproduce Figure 2.

TABLE 11 Efect ofPlacenta Circumvallata on the Mother and Foetus in 50 Consecutive Cases

Effect on the Mother

Haemorrhage during pregnancy . . . . . . 4 3 incomplete abortions

Premature rupture of membranes . . . . . . 3 all artificial rupture of membranes for toxaemia Abnormalities of the 3rd stage:

1 severe haemorrhage at 28 weeks

(a) Retention of membranes . . . . . . 7 partial

(b) Retention of placenta . . . . . . . . 2 (c) Post-partum haemorrhage of 20 ounces or more 11

4 complete

22 per cent (average of all deliveries 6 .2 per cent) Maternal mortality . . . . . . . . .. nil

Effect on the Foetus

Abortion . . . . . . . . . . , . 3 at 20, 24 and 24 weeks respectively Intra-uterinedeath . . . , . . . . . . 1 hysterotomy for ante-partum haemorrhage at 28

Neonatal death . . . . . . . . . . . . 1 prematurity; severe pre-eclamptic toxaemia; anuria Prematurity . . . . . . . . . . . . 2 severe ante-partum haemorrhage; severe pre-

Average birth weight . . . . . . . . . . 7 pounds 3 ounces (3,220 g.); (average of all births

Foetal survival . . . . . . . . . . . . 46

weeks

eclamptic toxaemia

6 pounds 15 ounces (3,108 g.))

_________

PLACENTA CIRCUMVALLATA 747 REFERENCES

Bartholomew, R. A., Colvin, E. D., Giimes, W. H., Fish, J. S., and Lester, W. M. (1953): Amer. J . Obstet. Gynec., 66, 1042.

L. M. (1947): Gynecozogicuz pathology. Saunders, Philadelphia. p. 518.

by Williams, 1927.)

Gynec., 39, 39.

Hunt, A. B., Mussey, R. D., and Fabe., J. E. (1947):

Kiistner, -. (1884): Cbl. Gynak., 8, 664. (Quoted by

Potter, E. L. (1952): Pathology of rhe fetus and newborn.

Schwab, -. (1895): Arch. Toco. Gyn&., 22. (Quoted by

Williams, J. W. (1927): Amer. J . Obsret. Gynec., 13, 1.

New Orleans med. surg. J., 100, 203.

Williams, 1927.)

Yearbook Publishers, Chicago. p. 23.

Williams, 1927.)

Herff, -. (1896): Z. Geburtsh. Gynuk., 35, 268. (Quoted

Hobbs, J. E., and Price, C. B. (1940): Amer. J. Obsret.