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Examination of the recently delivered placenta by phase contrast microscopy
Examination of the recently delivered placenta by phase contrast microscopy H.
ROBERT
Chicago,
MISENHIMER,
M.D.
Illinois
Phase contrast microscopic examination of the recently delivered placenta offers a readily available method of identifying abnormalities of the chorionic villi. This type of examination on 995 placentas from both normal patients and those with a variety of clinical abnormalities showed a statistically significant increase in the incidence of syncytial, stromal, and combined abnormalities in patients with these clinical problems. The pathogenesis of these abnormalities remains to be defined.
IT
SEEMS
REASONABLE
to
offers a method that is capable of detecting abnormalities of the villi that usually are not seen in fixed preparations. Furthermore. Aladjem2g 4 has shown a direct relationship between certain findings with this technique and the outcome of the pregnancy. In the report which follows, the results of a study designed to evaluate further the role of phase contrast microscopic examination of the recently delivered placenta as a clinically useful tool will be presented.
t!XpeCt
examination of the placenta to reveal changes that correlate with at least some of the abnormalities of the fetus and neonate. However, many years of experience with examination of this organ by standard histologic techniques have failed to achieve this correlation and, in fact, most often shown no abnormalities of the chorionic villi. Such frustrations are probably mainly responsible for the common practice of discarding the placenta without examination irrespective of the complications of the pregnancy or its outcome. In the past eight years, there have been several reports on the use of phase contrast microscopy to examine the terminal villi of the recently delivered placenta.*? 5 Most of these reports conclude that this technique From the Department of Obstetrics Gynecology, Rush-PresbyterianSt. Medical Center.
and Luke’s
Supported in part by a grant from Research and Education Committee the Rush-Presbyterian-St. Luke’s Medical Center.
the of ’
Presented at a meeting of the Gynecological Society, March
Chicago 17, 1972.
Received
20, 1972.
for publication
June
Material
and
methods
The placentas submitted for exarnination were refrigerated in plastic bags, without additives, from the time of delivery until examination, and care was taken to prevent freezing. Phase contrast microscopic examination was carried out within 24 hours in most cases, although our experience suggests that no morphologic changes occur in the placental tissue in the first 48 to 72 hours after delivery under these storage condi-, tions. A minimum of 4 fragments of tissue, one from each quadrant of the placenta, were teased from the approximate midpoint between the basal and chorionic plates. Each fragment was washed in a solution of 5 per cent dextrose in distilled water to remove as much maternal blood as possible; the fragment was suspended in a drop of the s:urte
Accepted for publication June 22, 1972. Reprint requests: Dr. H. Robert Misenhimer, Dept. of Ob./Gyn., RushPresbyterian-St. Luke’s Medical Center, I753 W. Congress Pkwy., Chicago, Illinois 60612. 796
Volume Numhrr
114 6
Examination
of
recently
delivered
placenta
797
Fig. 1. Phase contrast photomicrographs of normal villi. (Original magnification x200.) A, Fifteen weeks, showing a large villus with thick syncytium, a small capillary, and normal syncytial sprout formation. B, Twenty-four weeks, showing a decrease in the width of the villus and an increase in the size of the capillary. C, Thirty-six weeks, showing an increase in capillary size, a decrease in the thickness of the syncytium, and absence of syncytial sprouts. D, Thirty-nine weeks, showing marked tortuosity of the capillary, minimal stroma, and no sprouts.
solution, covered with a cover slip, and examined immediately. Throughout this study the nomenclature and definitions suggested by Alvarez5 and Aladjem* have been used. In all instances the microscopic examination was performed by the same individual without knowledge of the indication for placental examination. The study spanned 3 years in 2 hospitalsThe Baltimore City Hospitals, Baltimore, Maryland, and the Rush-Presbyterian-St. Luke’s Medical Center, Chicago, Illinoisand included more than 1,500 placentas which were examined by phase contrast microscopy. This report will deal with 995 of these specimens that were examined for the indications shown in Table I. The components of the individual terminal villi-the syncytium, the stroma, and the villus
capillary-were
the
focal
points
in
this
Table I. Indications
for placental
examination
Indication Normal pregnancy Premature rupture of membranes (PROM) Macrosomia (birth weight > 4,000 Gm. ) Premature infant (birth weight = 501 to 2,500 Gm.) Chronic hypertensive disease (chronic high blood pressure) Pre-eclampsia/eclampsia 1 min. Apgar score of 6 or less Diabetes mellitus Abruptio placentae Isoimmunization Total
No. 143 256 192 108 79 69 57 33 30 28 995
examination. The normal morphology and the expected changes in the appearance of the villi are illustrated in Fig. 1. The syncytium was studied to assess the
798
Misenhimer
Fie. 2. Phase contrast th; technique. (Origink edema. C, Villus edema.
uhotomicrosraphs which magnification x200.) D, Viilus degeneration.
degree of proliferation, judged by the number of syncytial sprouts that were present per 100 villi, and this sprout-villus index (SVI) was determined to be normal or abnormal in comparison to the normal values that have been reported by Aladjem.’ Because this index decreases with advancing maturation of the placenta, it was also necessary to estimate the age of the placenta. This was done by estimating the proportion of the villus that was occupied by the capillary and stromal-vascular ratio (SVK), as well as the degree of tortuosity of the capillary. Both the SVR and the tortuosity increase with advancing gestational age. Syncytial hypoplasia was diagnosed when the SW was less than expected for the degrer of maturation of the villi. Syncytial hyperplasia was reported in the more mature placentas when the SVI exceeded the normally small number of sprouts. The pattern of sprout formation was also examined. In the normal placenta sprouts
show some A, Abnormal
of the abnormalities sprout pattern.
described B, Subsynrytin!
by
form primarily at the free end of the villus and are attached to the parent \4lus by ‘I broad base. In some situations sprouts wcw seen along thtx lateral walls of the major slcm villi, or the sprouts which had formed at rhcb tip of the villus were being sloughed frorrl the villus by a reduction in t’nr siw of rhe attachment to a thin pedicle. These changes were diagnosed as an abnormal sprout pattern as is shown in Fig. 2> A. Subsyncytial edema is an abnormality assigned to the syncytium in this nomenclature, scheme and was diagnosed when villi contained an accumulation of fluidlike material interposed between the syncytium and the underlying stromn (Fig. 2, P The syncytium was also scrutinized for evidence of fragmentation of the syncytilim or the complete absence of the syncytium from the majority of the villi. The abnormalities of the stroma that wcrc found most commonly were ischemia, villus tlqcn~~ration, and villus tedem;:. I,ess i‘otil-
Volume Numhcr
114 6
Examination
Table II. Incidence
Clinical
of specific
disease of
6 or less
recently
delivered
placenta
799
abnormalities NO abnormalities (%I
condition
Normal pregnancy PROM Macrosomia Premature infant Chronic hypertensive Pre-eclampsia/eclampsia 1 min. Apgar score Diabetes mellitus Abruptio placentae Isoimmunization
of
67.1 47.4 44.8 21.3 38.0 43.5 40.3 33.3 40.0 32.1
manly, avascularity of the villus was diagnosed when no evidence of a capillary could be found, and intravillus hemorrhage was noted as a diagnosis when there was frank bleeding into the villus stroma. Villus &hernia was diagnosed when the villus capillary contained less than the normal amount of blood. This is the most subjective interpretation in this technique and the most difficult to evaluate. Villus degeneration is the abnormality characterized by complete replacement of the villus stroma and capillary by a fluidlike substance but with preservation of the syncytium (Fig. 2, D). Villus edema might more appropriately be called villus hypertrophy because the characteristics of this abnormality are enlargement of the entire villus without other changes except for an apparent decrease in the stroma-vascular ratio in the more advanced degrees of villus edema. The significance of this abnormality is thought to be a reduction in the surface area of the villus that is exposed to the intervillus space (Fig. 2, C i . Our initial evaluation of the results of this study has been to determine the frequency with which abnormalities of the syncytium, the stroma, or both (mixed) occurred in relationship to the maternal and fetal conditions shown in Table I. Results The incidence of abnormalities in each of the components of the villus is shown in Table II. Sixty-seven per cent of the placentas from
Syncytial abnormalities (%b) 4.2 7.8 3.6 15.7 12.6 7.2 7.0 3.0 6.7 0
Stromal abnormalities (%) 21.7 25.8 33.3 21.3 19.0 26.1 42.1 42.4 33.3 39.3
Mixed abnormalities (%I 7.0 19.5 18.2 41.7 30.4 23.2 10.5 21.2 20.0 28.6
normal patients had no abnormalities, whereas those from patients with the clinical conditions listed all had a statistically significant reduction in the number of normal placentas, as determined by phase contrast examination (p equal to or less than 0.01 for each condition, chi square test). Table III shows the distribution of specific abnormalities, by clinical condition, that occurred more often than normal. Only those abnormalities in which the increased incidence of occurrence was statistically significant are shown. Syncytial hypoplasia was seen most often in association with clinical conditions that resulted in delivery of premature infants. In the categories of PROM and Apgar score of 6 or less, the incidence of hypoplasia was not significantly different from normal if the incidence was corrected by removing the premature infants from the groups. Syncytial hyperplasia was found only in association with chronic hypertensive disease and a low one-minute Apgar score. Subsyncytial edema occurred in several conditions with no pattern of relationship discernible. The abnormalities listed as “other” include thickening of the syncytium, fragmentation of the syncytium, and, most commonly, abnormal patterns of sprout formation. The latter abnormality was seen only in association with syncytial hyperplasia. Stromal abnormalities occurred almost universally in association with these particular clinical conditions, with the exception of avascularity which was found only in cases of abruptio placentae.
800
Misenhimer
Table III. Specific
abnormalities Syncytial
Clinical
condition
Normal pregnancy PROM Macrosomia Premature infant Chronic HBP Pre-eclampsia/ eclampsia 1 min. Apgar score of 6 or less Diabetes mellitus Abruptio placentae Isoimmunization
r/o
that
hypoplasia
Syncytial
IP 0.001
58.3
0.001
hygerplasia
0.001
15.8
0.05
significant
greater
Subsyncytial
edema
%I@ 5.0 13.7 15.6 13.9 1.5.2
0.01 0.01 O.Or, 0.02
frequency
than
OthPr i:ncytml abnolmaliticc ---~ 5% / P 1.4
9.2 8.9
0.01
24.6
0.001
26.7 7.1
0.001 0.05
21.4
Comment
The results of this study confirm the reports of other investigators that phase contrast microscopic examination of the recently delivered placenta reveals a spectrum of abnormalities in the terminal chorionic villi that are rarely, if ever, appreciated by standard histologic techniques. Alvarez” and Aladjem’ provide evidence that many of the abnormalities seen in fresh tissue specimens are sufficiently altered or even destroyed by the dehydration of routine histologic procedures so as to make their identification impossible. The frequency with which some of the phase contrast abnormalities occur in specific
REFERENCES
Aladjem, S.: Obstet. Gynecol. Aladjem, S.: AM. J. OBSTET. 701-, 1968.
statistically
20.2
The correlation between identifiable abnormalities of the chorionic villi by standard histologic techniques and phase contrast microscopy was evaluated in 123 specimens studied by both methods. The chorionic villi were judged to be normal in 110 cases by standard microscopic examination of hema& toxylin and eosin-stained tissue, and in only 37 of these same placentas were the villi considered to be normal by phase contrast. This difference is statistically significant (p < 0.001) Furthermore, the abnormalities noted on the fixed preparations were not the same as those seen by phase contrast.
1. 2.
with
%lP 5.0
0 24.2
8.7
occurred
28,
GYNECOL.
1968. 101:
~I.001
10.0
‘LO5
0.01
clinical conditions, e.g.> the high incidence of syncytial hypoplasia in association with premature delivery, at least suggest that there, may be a cause-and-effect relationship.” However, at this time we have a poor understanding of the pathogenesis of the abnormalities, and, until such etiologic aspects ha\ P been defined, examination of the placenta will continue to be less than adequate :I?, ii means of assessing or understanding abnormal pregnancies. Despite this basic deficiency, the technique of phase contrast microscopy has several features that make its routine use in examination of the placenta a worthwhile addition to those currently employed. Two of these fentures are : 1. The simplicity and almost immediate availability following delivery provide a means of assessing another parameter that may influence the neonatal course. If thP pediatrician can be provided with informntion regarding the placenta, he may bc in n better position to outline the management of the sick infant. 2. Informtaion obtained from examination of the placenta by this technique ma)- help to broaden our understanding of the pathophysiology of abnormal pregnancies.
3. 32:
14.0
4. 5.
Aladjem, S.: J. Obstet. Gynaecol. Br. Commonw. 75: 1237, 1968. Aladjem, S.: Obstet. Gynecol. 38: 671, 1971. Alvarez, H.: Obstet. Gynecol. 23: 813, 1964.
in
Volume Number
normal
114 6
Examination
of
recently
delivered
placenta
801
pregnancy Intravillus
Avascularity
hemorrhage
%
P
0.7
10.0
70
0
0.02
/
Zschemia P
Villus
degeneration
Villus
edema
P
70
P
70
P
25.9 49.2 45.3 72.2
0.001 0.001 0.001
2.1 12.5 15.1 14.8 16.4
0.001 0.001 0.001 0.001
3.5 19.9 14.6 29.6 12.6
0.001 0.01 0.001 0.02
43.5
0.02
10.1
0.05
10.5
0.05
45.4 56.7 64.3
0.05 0.01 0.001
20.0
0.001
36.8 36.4 26.7 53.6
0.001 0.001 0.001 0.001
70
Discussion
DR. RALPH M. WYNN, Chicago, Illinois. The correlation of anatomic data with clinical experience is the key to progress in our field. Dr. Misenhimer’s phase contrast microscopy of the placenta is such an example, for which he deserves credit. Although the attempt to predict fetal outcome and neonatal course on the basis of histologic structure of the placenta is admirable, problems of technique and interpretation render these studies inaccurate and often misleading. My objections are those that I have already expressed with regard to the reports of Aladjem, the methods and conclusions of which the present investigation duplicates. Aladjem, who in turn based his work on that of Alvarez in Montevideo, attempted to assess fetal well-being by phase contrast microscopy of material obtained through transabdominal placental biopsy. The method proved impracticable and potentially dangerous. First, the sampling error in any blind biopsy of the placenta is enormous, as pointed out by numerous authors,l, 2 because of the normal variation in histologic structure from chorionic plate to basal plate, center to margin of the cotyledon, villus to villus, and, even, as shown by electron microscopy, within an individual villus. If, for example, the biopsy were obtained from an infarcted area of the placenta, the results would obviously be indicative of degeneration. Furthermore, the inherent risk of hemorrhage with this technique precluded further testing in women. Attempts were then made by Aladjem and repeated by Misenhimer to forecast neonatal course on the basis of the placental histologic structure, or, in other words, to identify the high-risk infant. Although biopsy of the delivered placenta involves
no hazard, attempts to base clinical management on the results of phase contrast microscopy are often misleading in individual cases; for it is well known that severely ill neonates may have placentas of which large portions appear essentially normal, whereas abnormal placentas may be associated with healthy newborn infants. The hypothesis of Aladjem and Misenhimer relates the degrees of hyperplasia and hypoplasia of the syncytium and various abnormalities of the villous stroma to placental function. It requires our acceptance of the simplistic concept that the placental exchange area in the terminal villi is essentially a measure of the functional integrity of the capillary bed when the vascular area is expressed as a percentage of the total villous area. Dr. Misenhimer examined one fragment of tissue from each quadrant of the placenta, with particular reference to the syncytium, villouz stroma, and capillaries. He related hypoplasia of the syncytium to placental insufficiency and hyperplasia to pre-eclampsia, hypertension, and diabetes, all of which may be associated with relative placental hypoxia. The syncytial sprouts, interpreted as hyperplasia, may, however, be tips of other villi not in focus in a particular planr. Sprouts, furthermore, may consist of hyperplastic, apparently healthy syncytium or degenerating clumps with pyknotic nuclei, as revealed by electron microscopy. The sprout-villus index is said to decrease with advancing maturation, but the age of the placenta was merely estimated by ascertaining the proportion of the villus that was occupied by capillaries-at best an imprecise technique and perhaps an example of circular reasoning. The terms “ischemia,” “edema,” “hem. are subjective ant orrhage,” and “degeneration”
802
Misenhimer
at most qualitative and not amenable to refined quantitation. Unpublished observations from my laboratory, as well as the recent report of Coles,:’ do not confirm the view that the villi accurately reflect the state of the fetus or that a few villi arr representative of the whole placenta. In fact, Coles shelved that the villi differed greatly in various parts of the placenta to the extent that examination of even large numbers of villi did not provide valuable information about the condition of the baby. Finally, since the systematic errors render the technique imprecise, it is unprofitable to waluate the accuracy of the method, since, by logical and statistical definitions, accuracy cannot possibly exceed precision.
I applaud Dr. Misenhimer’s attempt to cxamine histologically the freshly deliver4 plac.enta, the organ most seriously neglected 1)) clinicians and pathologists, btlt I mu\t I~VIV( judgment about the wisdom of basing clirlical management on the results of thc>c intr,w.lin!: studies REFERENCES
1, 2.
3.
Benirschke, K.: AM. J. OBSTET. GYXECCII.. 84: 1595, 196’. Wynn, R. M.: In Assali, N. S., editor: Biology of Gestation, New York, 1968, vol. 1, AradPmic Press, Inc., chap. 3. Coles, R. A.: AX. J. OBSTET. GYNEC:OI.. 1 II: 369. 1971.
ROBERT
Chicago,
MISENHIMER,
M.D.
Illinois
Phase contrast microscopic examination of the recently delivered placenta offers a readily available method of identifying abnormalities of the chorionic villi. This type of examination on 995 placentas from both normal patients and those with a variety of clinical abnormalities showed a statistically significant increase in the incidence of syncytial, stromal, and combined abnormalities in patients with these clinical problems. The pathogenesis of these abnormalities remains to be defined.
IT
SEEMS
REASONABLE
to
offers a method that is capable of detecting abnormalities of the villi that usually are not seen in fixed preparations. Furthermore. Aladjem2g 4 has shown a direct relationship between certain findings with this technique and the outcome of the pregnancy. In the report which follows, the results of a study designed to evaluate further the role of phase contrast microscopic examination of the recently delivered placenta as a clinically useful tool will be presented.
t!XpeCt
examination of the placenta to reveal changes that correlate with at least some of the abnormalities of the fetus and neonate. However, many years of experience with examination of this organ by standard histologic techniques have failed to achieve this correlation and, in fact, most often shown no abnormalities of the chorionic villi. Such frustrations are probably mainly responsible for the common practice of discarding the placenta without examination irrespective of the complications of the pregnancy or its outcome. In the past eight years, there have been several reports on the use of phase contrast microscopy to examine the terminal villi of the recently delivered placenta.*? 5 Most of these reports conclude that this technique From the Department of Obstetrics Gynecology, Rush-PresbyterianSt. Medical Center.
and Luke’s
Supported in part by a grant from Research and Education Committee the Rush-Presbyterian-St. Luke’s Medical Center.
the of ’
Presented at a meeting of the Gynecological Society, March
Chicago 17, 1972.
Received
20, 1972.
for publication
June
Material
and
methods
The placentas submitted for exarnination were refrigerated in plastic bags, without additives, from the time of delivery until examination, and care was taken to prevent freezing. Phase contrast microscopic examination was carried out within 24 hours in most cases, although our experience suggests that no morphologic changes occur in the placental tissue in the first 48 to 72 hours after delivery under these storage condi-, tions. A minimum of 4 fragments of tissue, one from each quadrant of the placenta, were teased from the approximate midpoint between the basal and chorionic plates. Each fragment was washed in a solution of 5 per cent dextrose in distilled water to remove as much maternal blood as possible; the fragment was suspended in a drop of the s:urte
Accepted for publication June 22, 1972. Reprint requests: Dr. H. Robert Misenhimer, Dept. of Ob./Gyn., RushPresbyterian-St. Luke’s Medical Center, I753 W. Congress Pkwy., Chicago, Illinois 60612. 796
Volume Numhrr
114 6
Examination
of
recently
delivered
placenta
797
Fig. 1. Phase contrast photomicrographs of normal villi. (Original magnification x200.) A, Fifteen weeks, showing a large villus with thick syncytium, a small capillary, and normal syncytial sprout formation. B, Twenty-four weeks, showing a decrease in the width of the villus and an increase in the size of the capillary. C, Thirty-six weeks, showing an increase in capillary size, a decrease in the thickness of the syncytium, and absence of syncytial sprouts. D, Thirty-nine weeks, showing marked tortuosity of the capillary, minimal stroma, and no sprouts.
solution, covered with a cover slip, and examined immediately. Throughout this study the nomenclature and definitions suggested by Alvarez5 and Aladjem* have been used. In all instances the microscopic examination was performed by the same individual without knowledge of the indication for placental examination. The study spanned 3 years in 2 hospitalsThe Baltimore City Hospitals, Baltimore, Maryland, and the Rush-Presbyterian-St. Luke’s Medical Center, Chicago, Illinoisand included more than 1,500 placentas which were examined by phase contrast microscopy. This report will deal with 995 of these specimens that were examined for the indications shown in Table I. The components of the individual terminal villi-the syncytium, the stroma, and the villus
capillary-were
the
focal
points
in
this
Table I. Indications
for placental
examination
Indication Normal pregnancy Premature rupture of membranes (PROM) Macrosomia (birth weight > 4,000 Gm. ) Premature infant (birth weight = 501 to 2,500 Gm.) Chronic hypertensive disease (chronic high blood pressure) Pre-eclampsia/eclampsia 1 min. Apgar score of 6 or less Diabetes mellitus Abruptio placentae Isoimmunization Total
No. 143 256 192 108 79 69 57 33 30 28 995
examination. The normal morphology and the expected changes in the appearance of the villi are illustrated in Fig. 1. The syncytium was studied to assess the
798
Misenhimer
Fie. 2. Phase contrast th; technique. (Origink edema. C, Villus edema.
uhotomicrosraphs which magnification x200.) D, Viilus degeneration.
degree of proliferation, judged by the number of syncytial sprouts that were present per 100 villi, and this sprout-villus index (SVI) was determined to be normal or abnormal in comparison to the normal values that have been reported by Aladjem.’ Because this index decreases with advancing maturation of the placenta, it was also necessary to estimate the age of the placenta. This was done by estimating the proportion of the villus that was occupied by the capillary and stromal-vascular ratio (SVK), as well as the degree of tortuosity of the capillary. Both the SVR and the tortuosity increase with advancing gestational age. Syncytial hypoplasia was diagnosed when the SW was less than expected for the degrer of maturation of the villi. Syncytial hyperplasia was reported in the more mature placentas when the SVI exceeded the normally small number of sprouts. The pattern of sprout formation was also examined. In the normal placenta sprouts
show some A, Abnormal
of the abnormalities sprout pattern.
described B, Subsynrytin!
by
form primarily at the free end of the villus and are attached to the parent \4lus by ‘I broad base. In some situations sprouts wcw seen along thtx lateral walls of the major slcm villi, or the sprouts which had formed at rhcb tip of the villus were being sloughed frorrl the villus by a reduction in t’nr siw of rhe attachment to a thin pedicle. These changes were diagnosed as an abnormal sprout pattern as is shown in Fig. 2> A. Subsyncytial edema is an abnormality assigned to the syncytium in this nomenclature, scheme and was diagnosed when villi contained an accumulation of fluidlike material interposed between the syncytium and the underlying stromn (Fig. 2, P The syncytium was also scrutinized for evidence of fragmentation of the syncytilim or the complete absence of the syncytium from the majority of the villi. The abnormalities of the stroma that wcrc found most commonly were ischemia, villus tlqcn~~ration, and villus tedem;:. I,ess i‘otil-
Volume Numhcr
114 6
Examination
Table II. Incidence
Clinical
of specific
disease of
6 or less
recently
delivered
placenta
799
abnormalities NO abnormalities (%I
condition
Normal pregnancy PROM Macrosomia Premature infant Chronic hypertensive Pre-eclampsia/eclampsia 1 min. Apgar score Diabetes mellitus Abruptio placentae Isoimmunization
of
67.1 47.4 44.8 21.3 38.0 43.5 40.3 33.3 40.0 32.1
manly, avascularity of the villus was diagnosed when no evidence of a capillary could be found, and intravillus hemorrhage was noted as a diagnosis when there was frank bleeding into the villus stroma. Villus &hernia was diagnosed when the villus capillary contained less than the normal amount of blood. This is the most subjective interpretation in this technique and the most difficult to evaluate. Villus degeneration is the abnormality characterized by complete replacement of the villus stroma and capillary by a fluidlike substance but with preservation of the syncytium (Fig. 2, D). Villus edema might more appropriately be called villus hypertrophy because the characteristics of this abnormality are enlargement of the entire villus without other changes except for an apparent decrease in the stroma-vascular ratio in the more advanced degrees of villus edema. The significance of this abnormality is thought to be a reduction in the surface area of the villus that is exposed to the intervillus space (Fig. 2, C i . Our initial evaluation of the results of this study has been to determine the frequency with which abnormalities of the syncytium, the stroma, or both (mixed) occurred in relationship to the maternal and fetal conditions shown in Table I. Results The incidence of abnormalities in each of the components of the villus is shown in Table II. Sixty-seven per cent of the placentas from
Syncytial abnormalities (%b) 4.2 7.8 3.6 15.7 12.6 7.2 7.0 3.0 6.7 0
Stromal abnormalities (%) 21.7 25.8 33.3 21.3 19.0 26.1 42.1 42.4 33.3 39.3
Mixed abnormalities (%I 7.0 19.5 18.2 41.7 30.4 23.2 10.5 21.2 20.0 28.6
normal patients had no abnormalities, whereas those from patients with the clinical conditions listed all had a statistically significant reduction in the number of normal placentas, as determined by phase contrast examination (p equal to or less than 0.01 for each condition, chi square test). Table III shows the distribution of specific abnormalities, by clinical condition, that occurred more often than normal. Only those abnormalities in which the increased incidence of occurrence was statistically significant are shown. Syncytial hypoplasia was seen most often in association with clinical conditions that resulted in delivery of premature infants. In the categories of PROM and Apgar score of 6 or less, the incidence of hypoplasia was not significantly different from normal if the incidence was corrected by removing the premature infants from the groups. Syncytial hyperplasia was found only in association with chronic hypertensive disease and a low one-minute Apgar score. Subsyncytial edema occurred in several conditions with no pattern of relationship discernible. The abnormalities listed as “other” include thickening of the syncytium, fragmentation of the syncytium, and, most commonly, abnormal patterns of sprout formation. The latter abnormality was seen only in association with syncytial hyperplasia. Stromal abnormalities occurred almost universally in association with these particular clinical conditions, with the exception of avascularity which was found only in cases of abruptio placentae.
800
Misenhimer
Table III. Specific
abnormalities Syncytial
Clinical
condition
Normal pregnancy PROM Macrosomia Premature infant Chronic HBP Pre-eclampsia/ eclampsia 1 min. Apgar score of 6 or less Diabetes mellitus Abruptio placentae Isoimmunization
r/o
that
hypoplasia
Syncytial
IP 0.001
58.3
0.001
hygerplasia
0.001
15.8
0.05
significant
greater
Subsyncytial
edema
%I@ 5.0 13.7 15.6 13.9 1.5.2
0.01 0.01 O.Or, 0.02
frequency
than
OthPr i:ncytml abnolmaliticc ---~ 5% / P 1.4
9.2 8.9
0.01
24.6
0.001
26.7 7.1
0.001 0.05
21.4
Comment
The results of this study confirm the reports of other investigators that phase contrast microscopic examination of the recently delivered placenta reveals a spectrum of abnormalities in the terminal chorionic villi that are rarely, if ever, appreciated by standard histologic techniques. Alvarez” and Aladjem’ provide evidence that many of the abnormalities seen in fresh tissue specimens are sufficiently altered or even destroyed by the dehydration of routine histologic procedures so as to make their identification impossible. The frequency with which some of the phase contrast abnormalities occur in specific
REFERENCES
Aladjem, S.: Obstet. Gynecol. Aladjem, S.: AM. J. OBSTET. 701-, 1968.
statistically
20.2
The correlation between identifiable abnormalities of the chorionic villi by standard histologic techniques and phase contrast microscopy was evaluated in 123 specimens studied by both methods. The chorionic villi were judged to be normal in 110 cases by standard microscopic examination of hema& toxylin and eosin-stained tissue, and in only 37 of these same placentas were the villi considered to be normal by phase contrast. This difference is statistically significant (p < 0.001) Furthermore, the abnormalities noted on the fixed preparations were not the same as those seen by phase contrast.
1. 2.
with
%lP 5.0
0 24.2
8.7
occurred
28,
GYNECOL.
1968. 101:
~I.001
10.0
‘LO5
0.01
clinical conditions, e.g.> the high incidence of syncytial hypoplasia in association with premature delivery, at least suggest that there, may be a cause-and-effect relationship.” However, at this time we have a poor understanding of the pathogenesis of the abnormalities, and, until such etiologic aspects ha\ P been defined, examination of the placenta will continue to be less than adequate :I?, ii means of assessing or understanding abnormal pregnancies. Despite this basic deficiency, the technique of phase contrast microscopy has several features that make its routine use in examination of the placenta a worthwhile addition to those currently employed. Two of these fentures are : 1. The simplicity and almost immediate availability following delivery provide a means of assessing another parameter that may influence the neonatal course. If thP pediatrician can be provided with informntion regarding the placenta, he may bc in n better position to outline the management of the sick infant. 2. Informtaion obtained from examination of the placenta by this technique ma)- help to broaden our understanding of the pathophysiology of abnormal pregnancies.
3. 32:
14.0
4. 5.
Aladjem, S.: J. Obstet. Gynaecol. Br. Commonw. 75: 1237, 1968. Aladjem, S.: Obstet. Gynecol. 38: 671, 1971. Alvarez, H.: Obstet. Gynecol. 23: 813, 1964.
in
Volume Number
normal
114 6
Examination
of
recently
delivered
placenta
801
pregnancy Intravillus
Avascularity
hemorrhage
%
P
0.7
10.0
70
0
0.02
/
Zschemia P
Villus
degeneration
Villus
edema
P
70
P
70
P
25.9 49.2 45.3 72.2
0.001 0.001 0.001
2.1 12.5 15.1 14.8 16.4
0.001 0.001 0.001 0.001
3.5 19.9 14.6 29.6 12.6
0.001 0.01 0.001 0.02
43.5
0.02
10.1
0.05
10.5
0.05
45.4 56.7 64.3
0.05 0.01 0.001
20.0
0.001
36.8 36.4 26.7 53.6
0.001 0.001 0.001 0.001
70
Discussion
DR. RALPH M. WYNN, Chicago, Illinois. The correlation of anatomic data with clinical experience is the key to progress in our field. Dr. Misenhimer’s phase contrast microscopy of the placenta is such an example, for which he deserves credit. Although the attempt to predict fetal outcome and neonatal course on the basis of histologic structure of the placenta is admirable, problems of technique and interpretation render these studies inaccurate and often misleading. My objections are those that I have already expressed with regard to the reports of Aladjem, the methods and conclusions of which the present investigation duplicates. Aladjem, who in turn based his work on that of Alvarez in Montevideo, attempted to assess fetal well-being by phase contrast microscopy of material obtained through transabdominal placental biopsy. The method proved impracticable and potentially dangerous. First, the sampling error in any blind biopsy of the placenta is enormous, as pointed out by numerous authors,l, 2 because of the normal variation in histologic structure from chorionic plate to basal plate, center to margin of the cotyledon, villus to villus, and, even, as shown by electron microscopy, within an individual villus. If, for example, the biopsy were obtained from an infarcted area of the placenta, the results would obviously be indicative of degeneration. Furthermore, the inherent risk of hemorrhage with this technique precluded further testing in women. Attempts were then made by Aladjem and repeated by Misenhimer to forecast neonatal course on the basis of the placental histologic structure, or, in other words, to identify the high-risk infant. Although biopsy of the delivered placenta involves
no hazard, attempts to base clinical management on the results of phase contrast microscopy are often misleading in individual cases; for it is well known that severely ill neonates may have placentas of which large portions appear essentially normal, whereas abnormal placentas may be associated with healthy newborn infants. The hypothesis of Aladjem and Misenhimer relates the degrees of hyperplasia and hypoplasia of the syncytium and various abnormalities of the villous stroma to placental function. It requires our acceptance of the simplistic concept that the placental exchange area in the terminal villi is essentially a measure of the functional integrity of the capillary bed when the vascular area is expressed as a percentage of the total villous area. Dr. Misenhimer examined one fragment of tissue from each quadrant of the placenta, with particular reference to the syncytium, villouz stroma, and capillaries. He related hypoplasia of the syncytium to placental insufficiency and hyperplasia to pre-eclampsia, hypertension, and diabetes, all of which may be associated with relative placental hypoxia. The syncytial sprouts, interpreted as hyperplasia, may, however, be tips of other villi not in focus in a particular planr. Sprouts, furthermore, may consist of hyperplastic, apparently healthy syncytium or degenerating clumps with pyknotic nuclei, as revealed by electron microscopy. The sprout-villus index is said to decrease with advancing maturation, but the age of the placenta was merely estimated by ascertaining the proportion of the villus that was occupied by capillaries-at best an imprecise technique and perhaps an example of circular reasoning. The terms “ischemia,” “edema,” “hem. are subjective ant orrhage,” and “degeneration”
802
Misenhimer
at most qualitative and not amenable to refined quantitation. Unpublished observations from my laboratory, as well as the recent report of Coles,:’ do not confirm the view that the villi accurately reflect the state of the fetus or that a few villi arr representative of the whole placenta. In fact, Coles shelved that the villi differed greatly in various parts of the placenta to the extent that examination of even large numbers of villi did not provide valuable information about the condition of the baby. Finally, since the systematic errors render the technique imprecise, it is unprofitable to waluate the accuracy of the method, since, by logical and statistical definitions, accuracy cannot possibly exceed precision.
I applaud Dr. Misenhimer’s attempt to cxamine histologically the freshly deliver4 plac.enta, the organ most seriously neglected 1)) clinicians and pathologists, btlt I mu\t I~VIV( judgment about the wisdom of basing clirlical management on the results of thc>c intr,w.lin!: studies REFERENCES
1, 2.
3.
Benirschke, K.: AM. J. OBSTET. GYXECCII.. 84: 1595, 196’. Wynn, R. M.: In Assali, N. S., editor: Biology of Gestation, New York, 1968, vol. 1, AradPmic Press, Inc., chap. 3. Coles, R. A.: AX. J. OBSTET. GYNEC:OI.. 1 II: 369. 1971.