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Placental calcifications
FETUS AND NEWBORN Placental calcifications A biophysical
0.
HASSLER,
Umea”,
and
histologic
study
M.D
Sweden
Thirty human placentas from cases with various types of pregnancy complications and 20 placentas from normal pregnancies were examined by microradiography. Four different types of calcification could be distinguished by this method: (I) large strongly radiopaque confluent calcifications on the maternal surface, (2) small weakly radiopaque flakelike calcifications within the placenta, (3) veiled weakly radiopaque calcifications within the parenchyma, and (4) perivascular weakly radiopaque calcifications. No type was found to be specifically related to any pathologic disorder. X-ray diflraction examination of the first two types showed that they consisted mainly of calcium hydroxyapatite.
FE T A L deaths in utero represent an important cause of mortality in the Western world and interest in them has increased greatly in recent years. The majority of these deaths are obscure, in regard to their nature, and at present arc commonly attributed to such diffuse causes as “placental insufficiency.” A large number of pathologic lesions, such as fibrinoid degeneration, cystic degeneration, calcification, and infarctions of various types, are well known to occur abundantly, even in placentas from otherwise uncomplicated pregnancies. The lesions have mostly only been studied qualitatively and not quantitatively, i.e., they have generally been seen in histologic sections which comprise a very small, usually selected part of the total volume. Because the classical qualitative studies have so far failed to reveal the cause of “placental insufficiency,” it was considered
desirable to try new and more quantitative methods. The aim of the present study was to examine for calcifications systematically, with microradiography, placentas from normal and abnormal pregnancies. Material
and
methods
A total of 50 placentas were examined during July-September. Thirty were from patients who had had various complications during pregnancy (Table I). The remaining 20 placentas were obtained from pregnancies which seemed normal. Thus, the length of the pregnancy was less than 2 weeks before or after the calculated time and the weight of the child 2,900-3,900 grams. The mothrr and child appeared healthy. The placentas xvere fixed in formalin for 16 hours. They were then dehydrated in rising concentrations of alcohol and stored in absolute alcohol until the microradiographic examinations, which were performed within 2 days, largely in the same way as in a previous w0rk.l At first the whole placenta
From the Department of Pathology II, lJnive7sity of Umed. Supported by a grant from the Swedish Medical Research Council.
348
Placental
Table I. Distribution
of vario,us calcifications
over the various Maternal
Total Stillborn
of
the child
or mother
baby
of
No. caSex
calcifications Degree
Veiled calcifications Degree
zzz / zz
zzz 1 zz
IZZ ( II
/ z
4 0 0 1000100
( z
3
4
0
Toxicosis; stillborn baby Stillborn, malformed baby Malformed (living) baby
1 1 1
0 0 1
Premature (living) .4sphyxia Rh immunization Rh immunization;
7 4 3 1
;
420:
0 0
3003000300~ 10 0
2
1
10
0
Toxicosis Diabetes Clontrols
3 3 20
1 2 8
20 10 10
2
0 0 6
30 30 13
Total
50
17
30
3
9
36
baby
low
estrogens
Low estrogens
“Degree area on thr
I = no calcification. microradiographic
Degree plate 250
II = calcified mm.2.
area
on
\vas examined on Kodalith Ortho Type 3 film (50 kv., FSD 110 cm.). Then 2 mm. thick slices were examined on Kodak Maximum Resolution Plates (30 kv., FSD 110 cm. 1L Three aluminum strips (99.9 per cent aluminum) 0.10, 0.15, and 0.20 mm. thick, respectively, were placed on the specimen during this examination, which was so timeconsuming that only slices covering 108 cm.” \vere examined and not the whole placenta. The slices were cut in such a way that all parts of the placenta were represented. With regard to each of the four types of cnlcifications, the placentas Lvere divided into three classes, depending on the occurrence of the calcification in question (Table I). The arcas were at first measured roughly on millimeter paprr and, lvhen it xvas not quite apparent to which group the placenta belonged, a more exact determination wxs made with a planimeter. Ten representative calcifications of each type lvere embedded and divided into thin sections (varying between 5 and 500 p) . The sections were re-examined with microradiography on Kodak High Kesolution Plates (20 kv.. FSI> 4.5 cm.) . Routine histologic sections were prepared from all placentas and several calcifications
349
parts of the material*
Small calcifications within placenta Degree
surface
Diagnosis
calcifications
1
0
0
Perivascular calcifications Degree
1 I
zzz 1 zz ( I -
4 0 100
0
4 I
10001001001
000
the
1000 1
microl-adiographic
100
51 20
01
10 20
00 01
0
13
1
3
5
0
6
<
0
19
100 101
00 00 0
plate
1
6007
50 rnn~.~.
1 1
300 3 17
0 0
44
0
Degree
III
0 3 5 =
3 3 17 45calcified
with representative microradiologic appearances. X-ray diffraction examination was performed in the same way as in preceding Lv0rks.l Representative calcifications of each of the two first-mentioned types were studied in 3 cases. The other two types did not occur in sufficiently large amounts to allow both diffraction and histologic examination. Results On the x-ray films of the whole placenta, as a rule, only the large confluent flakelike calcifications on the maternal surface could be easily recognized. The pattern of the variations resembled that described by Tindall and Scott.” The other types of calcification could not be seen on these films, except type 2, lvhen it showed confluence. In the microradiographic plates calcifications were seen in all placentas examined. Four kinds of calcification were distinguished : ( 1) large strongly radiopaque confluent flakelike calcifications on the maternal surface, (2) small, weakly radiopaque, flakelike calcifications within the placenta, (3) rveakly radiopaque, veiled calcifications within the parenchyma, and (4) perivascular, weakly radiopaque calcifications.
150
Hassler
Fig. 1. A, Microradiogram of maternal surface calcification, The calcification is strongly radiopaque and was formed by the confluence of flakelike calcifications. The placental parenchyma is at the bottom. (~30.) B, X-ray diffractogram from the same calcification shows that it consists mainly of calcium hydroxyapatite, but that small amounts of beta Caa( PO+)? (indicated by line 85.0) are also present. C, Histologic section through a maternal surface calcification. The decidua is at the top and the chorionk villi at the bottom. (van C&on’s stain. x160.)
Volume Number
103 3
Placental
Fig. 2. A, Small, Histologic with fibrin
flakelike calcifications within the weakly radiopaque, section through one of the calcifications in A. The calcification deep in the placenta among the villi. (van Gieson’s stain. x260.)
calcifications
placenta. (x40.) B, is situated together
351
Fig. 3. A, Veiled, weakly radiopaque calcifications within the placenta. (j7.j R, weakly radiopaque calcifications. (~180.) C. Histologic section through part of tion in A. The calcification occurred in a fibrin infarction. (Hematmylin and D, Histologic section through one perivascular calcification which is situatrd to lumen of the artery with erythrorytes is to thr right. (Hrmatoxylin and eosill.
1. Large, strongly radiopaque, confluent, flakelike calcifications on the maternal surface. These calcifications (Fig. 1. A) were generally more radiopaque than 0.20 mm. aluminum. They often became confluent to form a calcification that had a maximum diameter of several centimeters. They occurred on the basal (decidual) plate of the
Prrix-ascular. the c:dcificae[Gn. ‘4.50.) thv if>lt ‘I%(, ?~‘I~.
placenta. ‘They were the commonest type of calcification. They were not found to be especially common in any f)athologic states [Table I). They UYX commoner with inc.reasing maturity of the child. ‘The microradiologic examination of thin sections and the histologic examination showed that the calcifications occurred in the: intervillou~
Placental
space near the decidual surface or in the most superficial parts of the decidua (Fig. 1, C) . They occurred, as a rule, together with fibrin and fragments of necrotic decid11;1. T’h x-ra) diffraction examination shol\-cd calcium hydroxyapatite contents in all 3 specimens examined (Fig. 1, B) , and in 2 of them also small amounts (less than 25 per cent) of tricalcium phosphate were present. 2. Small, weakly radiopaque, flakelike calcifications within the placenta. These calcifications (Fig. 2, A) were as a rule less radiopaque than 0.15 mm. aluminum and the)- never conflowed to form calcifications larger than 5 mm. They were scattered deeply Tvithin the placenta and were almost as common as the first-mentioned type of calcification. They were not found to be particularly common in any pathologic state I Table I). They were commoner \+ith inc,rrasing maturity of the child. They Lverc regularly found in connection with fibrin j Fig. 2, R) . They occurred sometimes within \Ui and sometimes in the intcrvillous space. \Yhrn they \vmz seen within the villi, the lattcr ones were partly destroyed. Intervillous t&ificntions probably often started within \-illi that got destroyed so they became inter\illous. The calcifications \\-ere often seen at the border of fibrin infarcts, but they Lvere practically just as common within fibrin infarcts as outside them. The x-ray diffraction rsamination showed calcium hydroxyapatite \\-ith a slight admixture of tricalcium phosphate (less than 25 per cent in all 3 cases). 3. Veiled, weakly radiopaque calcifications within the placenta. They were less &me than 0.10 mm. aluminum. Detailed esarnination of radiograms of thin sections revealed that they were generally finely granular. The veiled calcifications (Fig. 3, A) had diameters that never exceeded 8 mm. and were not frequent (Table I). Histologic examination (Fig. 3, C) showed that they occurred as a rule in fibrin infarcts together with fibrin in the intervillous space. 4. Perivascular, weakly radiopaque calcifications. Thev were less dense than 0.10 mm.
calcifications
353
aluminum (Fig. 3, B) and were not very frequent (Table I). The microradiologic examination of thin sections and the histoIogic examination showed that they were situated in the periadventitial tissue of the vessels, together with fibrin (Fig. 3, D) . Comment
Radiologic studies of placenta calcifications t\-ere performed by Masters and Clayton’ and by Tindall and Scott.3 They used conventional x-rays and therefore were able to observe mainly the comparatively strong radiopaque calcifications on the maternal surface. With microradiography, it was now possible to distinguish four different types of calcification. The four types seem to occur rather independently of each other. The present results are therefore difficult to compare with those of previous investigators, which comprise the total contents of calcifications visible \\-ith conventional x-rays or determined chemically. However, none of the types of calcification now distinguished could be found to have anything to do with an) pathologic disorder. The calcifications on the maternal surface were often very dense and extensive, so that they comprised at least one third of the surface without any clinical signs. Because much smaller calcifications \vf’re disclosed in the present study than in the previous radiologic ones,2l 3 the frequency of placentas with calcifications was higher in the present work. The placenta calcifications may appear within the maternal tissues like many of the maternal surface calcifications or they may appear in the fetal tissues as most of the other calcifications. Because of the tissue destruction around the calcifications, it is often difficult to decide from the radiograms and histologic sections if the calcification has started in maternal or fetal tissues. REFERENCES
1. Has&r, ?. Masters, Gvnaec. 3. Tindall, Gynaec.
0.: J. Neurosurg. 27: 336, 1967. M.,. and Clayton, S. G.:. J. Obst. & Brit. Emu. 47: 437. 1940. V. R., and Scott,’ J. S.: J. Obst. & Brit. Comm. 72: 356, 1965.
0.
HASSLER,
Umea”,
and
histologic
study
M.D
Sweden
Thirty human placentas from cases with various types of pregnancy complications and 20 placentas from normal pregnancies were examined by microradiography. Four different types of calcification could be distinguished by this method: (I) large strongly radiopaque confluent calcifications on the maternal surface, (2) small weakly radiopaque flakelike calcifications within the placenta, (3) veiled weakly radiopaque calcifications within the parenchyma, and (4) perivascular weakly radiopaque calcifications. No type was found to be specifically related to any pathologic disorder. X-ray diflraction examination of the first two types showed that they consisted mainly of calcium hydroxyapatite.
FE T A L deaths in utero represent an important cause of mortality in the Western world and interest in them has increased greatly in recent years. The majority of these deaths are obscure, in regard to their nature, and at present arc commonly attributed to such diffuse causes as “placental insufficiency.” A large number of pathologic lesions, such as fibrinoid degeneration, cystic degeneration, calcification, and infarctions of various types, are well known to occur abundantly, even in placentas from otherwise uncomplicated pregnancies. The lesions have mostly only been studied qualitatively and not quantitatively, i.e., they have generally been seen in histologic sections which comprise a very small, usually selected part of the total volume. Because the classical qualitative studies have so far failed to reveal the cause of “placental insufficiency,” it was considered
desirable to try new and more quantitative methods. The aim of the present study was to examine for calcifications systematically, with microradiography, placentas from normal and abnormal pregnancies. Material
and
methods
A total of 50 placentas were examined during July-September. Thirty were from patients who had had various complications during pregnancy (Table I). The remaining 20 placentas were obtained from pregnancies which seemed normal. Thus, the length of the pregnancy was less than 2 weeks before or after the calculated time and the weight of the child 2,900-3,900 grams. The mothrr and child appeared healthy. The placentas xvere fixed in formalin for 16 hours. They were then dehydrated in rising concentrations of alcohol and stored in absolute alcohol until the microradiographic examinations, which were performed within 2 days, largely in the same way as in a previous w0rk.l At first the whole placenta
From the Department of Pathology II, lJnive7sity of Umed. Supported by a grant from the Swedish Medical Research Council.
348
Placental
Table I. Distribution
of vario,us calcifications
over the various Maternal
Total Stillborn
of
the child
or mother
baby
of
No. caSex
calcifications Degree
Veiled calcifications Degree
zzz / zz
zzz 1 zz
IZZ ( II
/ z
4 0 0 1000100
( z
3
4
0
Toxicosis; stillborn baby Stillborn, malformed baby Malformed (living) baby
1 1 1
0 0 1
Premature (living) .4sphyxia Rh immunization Rh immunization;
7 4 3 1
;
420:
0 0
3003000300~ 10 0
2
1
10
0
Toxicosis Diabetes Clontrols
3 3 20
1 2 8
20 10 10
2
0 0 6
30 30 13
Total
50
17
30
3
9
36
baby
low
estrogens
Low estrogens
“Degree area on thr
I = no calcification. microradiographic
Degree plate 250
II = calcified mm.2.
area
on
\vas examined on Kodalith Ortho Type 3 film (50 kv., FSD 110 cm.). Then 2 mm. thick slices were examined on Kodak Maximum Resolution Plates (30 kv., FSD 110 cm. 1L Three aluminum strips (99.9 per cent aluminum) 0.10, 0.15, and 0.20 mm. thick, respectively, were placed on the specimen during this examination, which was so timeconsuming that only slices covering 108 cm.” \vere examined and not the whole placenta. The slices were cut in such a way that all parts of the placenta were represented. With regard to each of the four types of cnlcifications, the placentas Lvere divided into three classes, depending on the occurrence of the calcification in question (Table I). The arcas were at first measured roughly on millimeter paprr and, lvhen it xvas not quite apparent to which group the placenta belonged, a more exact determination wxs made with a planimeter. Ten representative calcifications of each type lvere embedded and divided into thin sections (varying between 5 and 500 p) . The sections were re-examined with microradiography on Kodak High Kesolution Plates (20 kv.. FSI> 4.5 cm.) . Routine histologic sections were prepared from all placentas and several calcifications
349
parts of the material*
Small calcifications within placenta Degree
surface
Diagnosis
calcifications
1
0
0
Perivascular calcifications Degree
1 I
zzz 1 zz ( I -
4 0 100
0
4 I
10001001001
000
the
1000 1
microl-adiographic
100
51 20
01
10 20
00 01
0
13
1
3
5
0
6
<
0
19
100 101
00 00 0
plate
1
6007
50 rnn~.~.
1 1
300 3 17
0 0
44
0
Degree
III
0 3 5 =
3 3 17 45calcified
with representative microradiologic appearances. X-ray diffraction examination was performed in the same way as in preceding Lv0rks.l Representative calcifications of each of the two first-mentioned types were studied in 3 cases. The other two types did not occur in sufficiently large amounts to allow both diffraction and histologic examination. Results On the x-ray films of the whole placenta, as a rule, only the large confluent flakelike calcifications on the maternal surface could be easily recognized. The pattern of the variations resembled that described by Tindall and Scott.” The other types of calcification could not be seen on these films, except type 2, lvhen it showed confluence. In the microradiographic plates calcifications were seen in all placentas examined. Four kinds of calcification were distinguished : ( 1) large strongly radiopaque confluent flakelike calcifications on the maternal surface, (2) small, weakly radiopaque, flakelike calcifications within the placenta, (3) rveakly radiopaque, veiled calcifications within the parenchyma, and (4) perivascular, weakly radiopaque calcifications.
150
Hassler
Fig. 1. A, Microradiogram of maternal surface calcification, The calcification is strongly radiopaque and was formed by the confluence of flakelike calcifications. The placental parenchyma is at the bottom. (~30.) B, X-ray diffractogram from the same calcification shows that it consists mainly of calcium hydroxyapatite, but that small amounts of beta Caa( PO+)? (indicated by line 85.0) are also present. C, Histologic section through a maternal surface calcification. The decidua is at the top and the chorionk villi at the bottom. (van C&on’s stain. x160.)
Volume Number
103 3
Placental
Fig. 2. A, Small, Histologic with fibrin
flakelike calcifications within the weakly radiopaque, section through one of the calcifications in A. The calcification deep in the placenta among the villi. (van Gieson’s stain. x260.)
calcifications
placenta. (x40.) B, is situated together
351
Fig. 3. A, Veiled, weakly radiopaque calcifications within the placenta. (j7.j R, weakly radiopaque calcifications. (~180.) C. Histologic section through part of tion in A. The calcification occurred in a fibrin infarction. (Hematmylin and D, Histologic section through one perivascular calcification which is situatrd to lumen of the artery with erythrorytes is to thr right. (Hrmatoxylin and eosill.
1. Large, strongly radiopaque, confluent, flakelike calcifications on the maternal surface. These calcifications (Fig. 1. A) were generally more radiopaque than 0.20 mm. aluminum. They often became confluent to form a calcification that had a maximum diameter of several centimeters. They occurred on the basal (decidual) plate of the
Prrix-ascular. the c:dcificae[Gn. ‘4.50.) thv if>lt ‘I%(, ?~‘I~.
placenta. ‘They were the commonest type of calcification. They were not found to be especially common in any f)athologic states [Table I). They UYX commoner with inc.reasing maturity of the child. ‘The microradiologic examination of thin sections and the histologic examination showed that the calcifications occurred in the: intervillou~
Placental
space near the decidual surface or in the most superficial parts of the decidua (Fig. 1, C) . They occurred, as a rule, together with fibrin and fragments of necrotic decid11;1. T’h x-ra) diffraction examination shol\-cd calcium hydroxyapatite contents in all 3 specimens examined (Fig. 1, B) , and in 2 of them also small amounts (less than 25 per cent) of tricalcium phosphate were present. 2. Small, weakly radiopaque, flakelike calcifications within the placenta. These calcifications (Fig. 2, A) were as a rule less radiopaque than 0.15 mm. aluminum and the)- never conflowed to form calcifications larger than 5 mm. They were scattered deeply Tvithin the placenta and were almost as common as the first-mentioned type of calcification. They were not found to be particularly common in any pathologic state I Table I). They were commoner \+ith inc,rrasing maturity of the child. They Lverc regularly found in connection with fibrin j Fig. 2, R) . They occurred sometimes within \Ui and sometimes in the intcrvillous space. \Yhrn they \vmz seen within the villi, the lattcr ones were partly destroyed. Intervillous t&ificntions probably often started within \-illi that got destroyed so they became inter\illous. The calcifications \\-ere often seen at the border of fibrin infarcts, but they Lvere practically just as common within fibrin infarcts as outside them. The x-ray diffraction rsamination showed calcium hydroxyapatite \\-ith a slight admixture of tricalcium phosphate (less than 25 per cent in all 3 cases). 3. Veiled, weakly radiopaque calcifications within the placenta. They were less &me than 0.10 mm. aluminum. Detailed esarnination of radiograms of thin sections revealed that they were generally finely granular. The veiled calcifications (Fig. 3, A) had diameters that never exceeded 8 mm. and were not frequent (Table I). Histologic examination (Fig. 3, C) showed that they occurred as a rule in fibrin infarcts together with fibrin in the intervillous space. 4. Perivascular, weakly radiopaque calcifications. Thev were less dense than 0.10 mm.
calcifications
353
aluminum (Fig. 3, B) and were not very frequent (Table I). The microradiologic examination of thin sections and the histoIogic examination showed that they were situated in the periadventitial tissue of the vessels, together with fibrin (Fig. 3, D) . Comment
Radiologic studies of placenta calcifications t\-ere performed by Masters and Clayton’ and by Tindall and Scott.3 They used conventional x-rays and therefore were able to observe mainly the comparatively strong radiopaque calcifications on the maternal surface. With microradiography, it was now possible to distinguish four different types of calcification. The four types seem to occur rather independently of each other. The present results are therefore difficult to compare with those of previous investigators, which comprise the total contents of calcifications visible \\-ith conventional x-rays or determined chemically. However, none of the types of calcification now distinguished could be found to have anything to do with an) pathologic disorder. The calcifications on the maternal surface were often very dense and extensive, so that they comprised at least one third of the surface without any clinical signs. Because much smaller calcifications \vf’re disclosed in the present study than in the previous radiologic ones,2l 3 the frequency of placentas with calcifications was higher in the present work. The placenta calcifications may appear within the maternal tissues like many of the maternal surface calcifications or they may appear in the fetal tissues as most of the other calcifications. Because of the tissue destruction around the calcifications, it is often difficult to decide from the radiograms and histologic sections if the calcification has started in maternal or fetal tissues. REFERENCES
1. Has&r, ?. Masters, Gvnaec. 3. Tindall, Gynaec.
0.: J. Neurosurg. 27: 336, 1967. M.,. and Clayton, S. G.:. J. Obst. & Brit. Emu. 47: 437. 1940. V. R., and Scott,’ J. S.: J. Obst. & Brit. Comm. 72: 356, 1965.