- Email: [email protected]
Hemolytic Disease Associated with the Rh Factor in Twin Pregnancies
HEMOLYTIC DISEASE ASSOCIAT.E:D WITH THE Rh FACTOR IN TWIN PREGNANCIES':' EuGENE
A. Co.NTI, M.D., :B'.A.C.S. AND Jon!'\ W. GLE:!'\K, M.D., Pn'TSBURGH, (Prom the Department of Obstttrics, Pittsbttrgh Hospital)
PA.
~
.:\LARCH 23, 1945, we delivered a primipara of twins, the first a normal healthy male, the second a stillborn macerated female presenting a typical 0 picture of hydrops fetalis. Rh studies on the blood of the parents and the surviving child confirmed the diagnosis and led us to a perusal of our records of stillbirths and neonatal deaths in multiple pregnancies to study similar instances of erythroblastosis occurring in twin pregnancies. One hundred ten multiple pregnancies (one hundred nine twin, one triplet) were reviewed. In 22 cases, one or both children were stillborn or neonatal deaths. Sixteen were eliminated from further investigation because of incompleteness of records, grand multiparity mitigating against Rh incompatibility as a factor, absence of clinical signs of hemolytic disease of the newborn, or the presence of some definite causation unrelated to the Rh factor. The remaining six were studied clinically and serologically in so far as the limitations of our antisera would permit, and the results are herein presented. Stratton, Langley, and Lister 1 have reported an Rh-negative mother who in her second pregnancy bore twins who were Rh positive but of different genotypes. The female child was normal. The male died on the fourth day of hemolytic disease. Aaburg and Roby 2 describe the case of a woman who in her third pregnancy produced a male and female twin which presented two varieties of erythroblastosis (the first icterus gravis, the second hydrops). Both were Rh positive, the mother Rh negative. This case strengthens an impression which we derived :from a study of one of our cases (No. 3) that there is a difference in the severity of effect in twins exposed to Rh antibodies, although in our own the offspring were monozygotic and in the one recounted by Aaburg were dizygotic. Wiener 3 reports a twin pregnancy (the patient's eighth) in which the male twin was Rh negative and normal and the female died within thirteen hours of icterus gravis. The incidence of fetal hemolytic disease resulting from the deleterious effect of transmitted maternal antibodies is difficult to determine. The combination of an Rh-negative wife and an Rh-positive husband occurs once in about thirteen marriages of white people.< Not every Rh-negative person exposed to Rh-positive blood becomes sensitized to the Rh factor. Individuals differ in the ease with which they can be sensitized, probably depending on some hereditary constitutional quality, so that in the average only about one in 2.5 to 50 Rhnegative persons exposed to the Rh antigen becomes sensitized. Occasional occurrence of hemolytic disease when the cnother is Rh positive has been attributed to subtypes of Rh and the Hr factor. 3 The mere fact that the patient's blood is Rh negative is not proof that Rh incompatibility is responsible :for the pathologic state. One must prove in addition that sensitization to the Rh factor has occurred. To do this, facilities for determining the presence of blocking as well as agglutinating antibodies are necessary. 5 Blocking antibodies are prob*Read before the Pittsburgh Obstetrical and Gynecological Society, Feb. 4, 1946.
446
ably more significant oJ' hemolytic disease beeause theyible. ia Practically, this is not feasible. As a matter of fact, we have had to discard spedmens of the common human anti-Rh sera because they were not sufficiently potent to give reliable reactions. We agree with I;evine that a pooling of material for the production of antisera in every community ;vould be advantageous in maintaining adequate supplies of the various t,vpcs. 6 Our serum is the standard anti-Rh, now designated anti-Rh 1 containing the agglutinins anti-Rh and anti-Rh 1 . 'rABLE
r.
ME"'DELIAx IXHBRnAxcE oy DmiiNAX'r CrrARACTERrs·rrcs
:l.
50% Rlirh .50% .Rhrh
4. 5. G.
:l5% rhrh
=
Table I presents the ::Vfendelian inheritance of the Rh factor which is a dominant characteristic. RhRh represents a condition in which similar genes have been derived from both parents and the individual is duplex (homozygous) as regards the character. Rhrh represents a condition in which the individual has received the gene from only one parent and is therefore simplex (heterozygous) with regard to the character; J1alf of the gametes of such an individual will have the gene and half will lack it. Lastly rhrh represents absence of the factor and such an individual is nullipex (Rh negative). He or she will not have the g·ene represented in any of the gametes and cannot, of course, transmit a trait represented by it.' We shall attempt to designate into which class each family group that we have analyzed will fall. CASE
1.-
:B"ather Rh positive *Rhrh
+
Mother Rh negative rhrh
First Twin Rh-negative male 50% 1·hrh
=
+
Second Twin Hh-positive female stil!bom 50% Rhrh
The second twin v\'e assume was Rh plw.; bec:.n1se of ite:; typical hydrops. It is unusual to encounter erythroblastosis where a mother has not been previously sensitized by transfusion or pregnancy. Levine has stated that the capacity to produce anti-Rh agglutinins differs in individual subjects so that in some women tho first pregnancy may result in an erythroblastotic infanU There is the speculative possibility that the blood of the surviving twin also produced antibodies which hastened the demise of its womb mate. Levine has also stressed the importanee of determining the homoor heterozygocity of the male parent in prognosticating the patient's percentage chance of having a normal ( R11-negative) child onee EJhe has become sensitized to the Rh factor. 8 In the above case the ehance in future pregnancies will be one in two. CASE
2.-
l<'ather Rh positive
Mother Rh negative rhrh
RhHh
rhrh
*Rhrh
or
Ji'irst Twin Rh-positive male 50% rhrh
*Refr>l'R lo Mendelian gr·oup in Table
100% Rhrh
r.
Second Twin Rh·positive male stillborn 50% Rhrh
448
AMEinCAN JOURNAL OF OBS'rETRICS AND GYNECOLOGY
In Case 2 the pregnancy was full te11.n and uncomplicated. The first child was delivered by outlet forceps. He was quite anemic but survived with massive doses of vitamin K. The second was a macerated fetus with an edematous bloated body and a shapeless cranium. Follow-up three and one-half years later revealed the survivor to be physically fairly well developed, but of a mental age of about six months. Wiener 5 has referred to the occurrence of feeblemindedness as a result of erythroblastosis and ascribes it to the occurrence of kernicterus or portal cirrhosis. This case also occurred in a first pregnancy without previous sensitization. It can be logically assumed that presence of monozygotic Rhpositive twins will resiJlt in a proportionately increased response within the maternal circulation. CASE
Father Rh positive
Mother Rh negative
*Rhrh
t
rhrh
RhRh
t
rhrh
or
Second Twins Rh-positive :female Rh-positive female stillborn 50% Rhrh
First Twins Rh-positive male Rh-positive :female 50% rhrh 100% Rhrh
'rhe first twins of this mating in Case 3 are a normal boy and girl past six years of age. The second set was born three and a half years ago. They were monozygotic twins born some weeks prematurely. The first girl weighed 4 lb., 13 oz., and exhibited a moderate anemia at birth. She survived after prolonged hospital care and is now apparently normal. The second child was stillborn, smaller, and presented the typical picture of an icterus gravis. The accepted criteria of erythroblastosis are present in this family, the manifestations becoming evident after sensitization by the first set of Hh-positive twins. The second twins again demonstrate varying response to antibody exposure or perhaps a difference in priority or accessibility to the maternal antigens. CASE
4.-
Father Rh positive
Mother Rh positive
·*Rhrh
+
Rhrh
RhRh
+
Rhrh
RhRh
t
RhRh
First Child Rh-positive female or or
25% RhRh t 50% Rhrh
t
Twins Rh-positive female Rh-positive female stillborn 25% rhrh
50% RhRh t 50% Rhrh 100% RhRh
In Case 4 this patient had had a spontaneous abortion between her first and second pregnancies. 'l'he first child was quite normal. The twins were born at thirty-four weeks. The stillborn female was small, compressed, with parchment-like yellow skin, a picture of fetus papyraceous. The survivor ·weighed 3 lb., 14 oz., and was not vigorous. The head was disproportionally large with wide fontanels. A difficult feeding problem was presented and hospitalization was prolonged. At eighteen months the <:hild is physically well deevloped but mentally greatly retarded. This case is included because of its similarity to Case 2. The history is fairly typical of Rh incompatibility which is, however, disproved by the serologic findings. The unhappy result in the living twin must be conceded to simple prematurity unless we admit the possible responsibility of a blood factor which we were unable to determine. •Refers to Mendelian group In T11.ble I.
CONTI AND GLENN: '
CASE
HEJ.IWLYTIC DISEASE TN TWIN PREGNANCIES
4;49
5.-
Father Rh poRitive *Rhrh
Mother Rh
po~itive
Rhrh
J!'irst Child Rh positive female 25% RhRh
Twins
Rh negative male Rh negative male 50% Rhrh 25% rhrh
The twin pregnancy in Case 5 was preceded by the delivery of a normal female two years before. The second twin was a normal boy now six months old. The first was a male weighing 6 lb., 11 oz. The head was large with wide ~utures and fontanels. Respirations were poor and the skin was very pale. Beginning on the second day there was some dark red bleeding from mucous membranes. He continued poorly and died eleven days after delivery. Unfortunately an Rh determination was not done and we have placed the child in his brother's Rh category because the pregnancy was monochorial. 'l'he diagnosis at autopsy was immaturity. There was no evidence of intracranial hemorrhage. However, in view of the anemia, bleeding from mucous membranes, we believe this child's condition might be logically explained by the presence of an Hr factor. Levine"' has demonstrated the presence of anti-Hr agglutinins in the blood of Rh-positive mothers of Rh-negative children who showed erythroblastosis. We have had both an Rh-positive infant of an Rh-negative mother and a negative infant of a positive mother who were well at birth and between the third and fourth days developed melena. Both were promptly controiled by transfusions of Rh-negative blood and \vithdrawal from breast feeding. CASE
6.-
Second Child Twins Father Mother First Child Rh positive Rh positive Rh-positive male Rh-positive female Rh-negative male Rh-negative mille Rhrh + Rhrh 25% RhRh + 50% Rhrh + 25% :rhrh
'l'wo normal children preceded the twins. The third pregnancy was uneventful. Labor began at thirty-five weeks and was quite easy. The first infant was a 4 lb., 10 oz. male who survived a feeding problem and is now 6 years old. The second was a 5 lb., 7 oz. male who was pale and apneic at birth, and died thirty-six hours later. Autopsy revealed an intradural hemorrhage and atalectasis. We have seen a fatal intracranial hemorrhage in the second child (Hh positive) of an Rh-negative mother and an Rh-positive father. It could be coincidence, but it seems reasonable to assume that intracranial bleeding- is as likely to result from hemolytic disease as is bleeding in other areas. The above case could be explained by an Hr factor, as was Case 5. We feel that further study and prolonged observation will reveal the Rh or other blood factors as the offenders in conditions whose explanations as such seem illogical at present. Levine has pointed out that the distribution o:f the Rh factor is limited to the red blood cells. In view of this, is it not illogi<:al to speculate on the. part that agglutinins may play in the production of fetal abnormalities such as hydrocephalus, anencephalus, spina bifida, amputation of extremities, etc.? .And yet we have noted, as have many others9 ' 12 the higher incidence of such conditions in families with proved parental Rh incompatibility. Summary 1. A series of multiple pregnancies has been studied. 2. Six cases which clinically and serologically suggested Rh incompatibility have been investigated and discussed in detail. •Refers to Mendelian !!rroup In 1'able ! .
450
AMERICAK JOURNAL OF OBSTETRICS AKD GYKECOLOGY
References l. Stratton! F., Langley, F. A., and. Listel) U.: Brit. M .•J. 1 ~ 151-15~, 1945. ·> Aaburg, 1!. E.J and Roby, C.: A!\f. J. UBST. & GYNEC. 50: .J48, 194u. 3. Wiener! A. S.: .J . Lab. & Clin. Med. 30: 395! 661, 957, 1945.
4. Levine, Philip: Arch. Path. 37: 83-90! 1944. 5. Wiener, A. S., Wexler, I. B., and Gamrin, E.: Am. J. Dis. Child. 68: 317-323, HlH. 6. Personal communication. i. Guyer, Michael F.: Being Well-Born, Indianapolis, 1927, Bohbs-:Merril Co. 8. Levine, Pl1ilip: Human Fertil. 9: 65-72, 1944. AM. ,J. OBST. & GYNEC. 46: 827, 1943. fl. Schwartz, Harold A., and Levine, Philip: 10. \Yiener, A. S., Davidsohn, T., and Pottnr, E. L.: .r. Exper. :\fed. 81: 63-72, lfl±5. 11. Levine, Philip: West; .J. Surg. 50: 468-475, 1942. !2. Traut, H. 11'., Mcivor, B. C., Howard! J., Lucia, S. P., and Charvet, L.: ~~M. J. OBST. & GYKEC. 50: 722, 1945.
A. Co.NTI, M.D., :B'.A.C.S. AND Jon!'\ W. GLE:!'\K, M.D., Pn'TSBURGH, (Prom the Department of Obstttrics, Pittsbttrgh Hospital)
PA.
~
.:\LARCH 23, 1945, we delivered a primipara of twins, the first a normal healthy male, the second a stillborn macerated female presenting a typical 0 picture of hydrops fetalis. Rh studies on the blood of the parents and the surviving child confirmed the diagnosis and led us to a perusal of our records of stillbirths and neonatal deaths in multiple pregnancies to study similar instances of erythroblastosis occurring in twin pregnancies. One hundred ten multiple pregnancies (one hundred nine twin, one triplet) were reviewed. In 22 cases, one or both children were stillborn or neonatal deaths. Sixteen were eliminated from further investigation because of incompleteness of records, grand multiparity mitigating against Rh incompatibility as a factor, absence of clinical signs of hemolytic disease of the newborn, or the presence of some definite causation unrelated to the Rh factor. The remaining six were studied clinically and serologically in so far as the limitations of our antisera would permit, and the results are herein presented. Stratton, Langley, and Lister 1 have reported an Rh-negative mother who in her second pregnancy bore twins who were Rh positive but of different genotypes. The female child was normal. The male died on the fourth day of hemolytic disease. Aaburg and Roby 2 describe the case of a woman who in her third pregnancy produced a male and female twin which presented two varieties of erythroblastosis (the first icterus gravis, the second hydrops). Both were Rh positive, the mother Rh negative. This case strengthens an impression which we derived :from a study of one of our cases (No. 3) that there is a difference in the severity of effect in twins exposed to Rh antibodies, although in our own the offspring were monozygotic and in the one recounted by Aaburg were dizygotic. Wiener 3 reports a twin pregnancy (the patient's eighth) in which the male twin was Rh negative and normal and the female died within thirteen hours of icterus gravis. The incidence of fetal hemolytic disease resulting from the deleterious effect of transmitted maternal antibodies is difficult to determine. The combination of an Rh-negative wife and an Rh-positive husband occurs once in about thirteen marriages of white people.< Not every Rh-negative person exposed to Rh-positive blood becomes sensitized to the Rh factor. Individuals differ in the ease with which they can be sensitized, probably depending on some hereditary constitutional quality, so that in the average only about one in 2.5 to 50 Rhnegative persons exposed to the Rh antigen becomes sensitized. Occasional occurrence of hemolytic disease when the cnother is Rh positive has been attributed to subtypes of Rh and the Hr factor. 3 The mere fact that the patient's blood is Rh negative is not proof that Rh incompatibility is responsible :for the pathologic state. One must prove in addition that sensitization to the Rh factor has occurred. To do this, facilities for determining the presence of blocking as well as agglutinating antibodies are necessary. 5 Blocking antibodies are prob*Read before the Pittsburgh Obstetrical and Gynecological Society, Feb. 4, 1946.
446
ably more significant oJ' hemolytic disease beeause they
r.
ME"'DELIAx IXHBRnAxcE oy DmiiNAX'r CrrARACTERrs·rrcs
:l.
50% Rlirh .50% .Rhrh
4. 5. G.
:l5% rhrh
=
Table I presents the ::Vfendelian inheritance of the Rh factor which is a dominant characteristic. RhRh represents a condition in which similar genes have been derived from both parents and the individual is duplex (homozygous) as regards the character. Rhrh represents a condition in which the individual has received the gene from only one parent and is therefore simplex (heterozygous) with regard to the character; J1alf of the gametes of such an individual will have the gene and half will lack it. Lastly rhrh represents absence of the factor and such an individual is nullipex (Rh negative). He or she will not have the g·ene represented in any of the gametes and cannot, of course, transmit a trait represented by it.' We shall attempt to designate into which class each family group that we have analyzed will fall. CASE
1.-
:B"ather Rh positive *Rhrh
+
Mother Rh negative rhrh
First Twin Rh-negative male 50% 1·hrh
=
+
Second Twin Hh-positive female stil!bom 50% Rhrh
The second twin v\'e assume was Rh plw.; bec:.n1se of ite:; typical hydrops. It is unusual to encounter erythroblastosis where a mother has not been previously sensitized by transfusion or pregnancy. Levine has stated that the capacity to produce anti-Rh agglutinins differs in individual subjects so that in some women tho first pregnancy may result in an erythroblastotic infanU There is the speculative possibility that the blood of the surviving twin also produced antibodies which hastened the demise of its womb mate. Levine has also stressed the importanee of determining the homoor heterozygocity of the male parent in prognosticating the patient's percentage chance of having a normal ( R11-negative) child onee EJhe has become sensitized to the Rh factor. 8 In the above case the ehance in future pregnancies will be one in two. CASE
2.-
l<'ather Rh positive
Mother Rh negative rhrh
RhHh
rhrh
*Rhrh
or
Ji'irst Twin Rh-positive male 50% rhrh
*Refr>l'R lo Mendelian gr·oup in Table
100% Rhrh
r.
Second Twin Rh·positive male stillborn 50% Rhrh
448
AMEinCAN JOURNAL OF OBS'rETRICS AND GYNECOLOGY
In Case 2 the pregnancy was full te11.n and uncomplicated. The first child was delivered by outlet forceps. He was quite anemic but survived with massive doses of vitamin K. The second was a macerated fetus with an edematous bloated body and a shapeless cranium. Follow-up three and one-half years later revealed the survivor to be physically fairly well developed, but of a mental age of about six months. Wiener 5 has referred to the occurrence of feeblemindedness as a result of erythroblastosis and ascribes it to the occurrence of kernicterus or portal cirrhosis. This case also occurred in a first pregnancy without previous sensitization. It can be logically assumed that presence of monozygotic Rhpositive twins will resiJlt in a proportionately increased response within the maternal circulation. CASE
Father Rh positive
Mother Rh negative
*Rhrh
t
rhrh
RhRh
t
rhrh
or
Second Twins Rh-positive :female Rh-positive female stillborn 50% Rhrh
First Twins Rh-positive male Rh-positive :female 50% rhrh 100% Rhrh
'rhe first twins of this mating in Case 3 are a normal boy and girl past six years of age. The second set was born three and a half years ago. They were monozygotic twins born some weeks prematurely. The first girl weighed 4 lb., 13 oz., and exhibited a moderate anemia at birth. She survived after prolonged hospital care and is now apparently normal. The second child was stillborn, smaller, and presented the typical picture of an icterus gravis. The accepted criteria of erythroblastosis are present in this family, the manifestations becoming evident after sensitization by the first set of Hh-positive twins. The second twins again demonstrate varying response to antibody exposure or perhaps a difference in priority or accessibility to the maternal antigens. CASE
4.-
Father Rh positive
Mother Rh positive
·*Rhrh
+
Rhrh
RhRh
+
Rhrh
RhRh
t
RhRh
First Child Rh-positive female or or
25% RhRh t 50% Rhrh
t
Twins Rh-positive female Rh-positive female stillborn 25% rhrh
50% RhRh t 50% Rhrh 100% RhRh
In Case 4 this patient had had a spontaneous abortion between her first and second pregnancies. 'l'he first child was quite normal. The twins were born at thirty-four weeks. The stillborn female was small, compressed, with parchment-like yellow skin, a picture of fetus papyraceous. The survivor ·weighed 3 lb., 14 oz., and was not vigorous. The head was disproportionally large with wide fontanels. A difficult feeding problem was presented and hospitalization was prolonged. At eighteen months the <:hild is physically well deevloped but mentally greatly retarded. This case is included because of its similarity to Case 2. The history is fairly typical of Rh incompatibility which is, however, disproved by the serologic findings. The unhappy result in the living twin must be conceded to simple prematurity unless we admit the possible responsibility of a blood factor which we were unable to determine. •Refers to Mendelian group In T11.ble I.
CONTI AND GLENN: '
CASE
HEJ.IWLYTIC DISEASE TN TWIN PREGNANCIES
4;49
5.-
Father Rh poRitive *Rhrh
Mother Rh
po~itive
Rhrh
J!'irst Child Rh positive female 25% RhRh
Twins
Rh negative male Rh negative male 50% Rhrh 25% rhrh
The twin pregnancy in Case 5 was preceded by the delivery of a normal female two years before. The second twin was a normal boy now six months old. The first was a male weighing 6 lb., 11 oz. The head was large with wide ~utures and fontanels. Respirations were poor and the skin was very pale. Beginning on the second day there was some dark red bleeding from mucous membranes. He continued poorly and died eleven days after delivery. Unfortunately an Rh determination was not done and we have placed the child in his brother's Rh category because the pregnancy was monochorial. 'l'he diagnosis at autopsy was immaturity. There was no evidence of intracranial hemorrhage. However, in view of the anemia, bleeding from mucous membranes, we believe this child's condition might be logically explained by the presence of an Hr factor. Levine"' has demonstrated the presence of anti-Hr agglutinins in the blood of Rh-positive mothers of Rh-negative children who showed erythroblastosis. We have had both an Rh-positive infant of an Rh-negative mother and a negative infant of a positive mother who were well at birth and between the third and fourth days developed melena. Both were promptly controiled by transfusions of Rh-negative blood and \vithdrawal from breast feeding. CASE
6.-
Second Child Twins Father Mother First Child Rh positive Rh positive Rh-positive male Rh-positive female Rh-negative male Rh-negative mille Rhrh + Rhrh 25% RhRh + 50% Rhrh + 25% :rhrh
'l'wo normal children preceded the twins. The third pregnancy was uneventful. Labor began at thirty-five weeks and was quite easy. The first infant was a 4 lb., 10 oz. male who survived a feeding problem and is now 6 years old. The second was a 5 lb., 7 oz. male who was pale and apneic at birth, and died thirty-six hours later. Autopsy revealed an intradural hemorrhage and atalectasis. We have seen a fatal intracranial hemorrhage in the second child (Hh positive) of an Rh-negative mother and an Rh-positive father. It could be coincidence, but it seems reasonable to assume that intracranial bleeding- is as likely to result from hemolytic disease as is bleeding in other areas. The above case could be explained by an Hr factor, as was Case 5. We feel that further study and prolonged observation will reveal the Rh or other blood factors as the offenders in conditions whose explanations as such seem illogical at present. Levine has pointed out that the distribution o:f the Rh factor is limited to the red blood cells. In view of this, is it not illogi<:al to speculate on the. part that agglutinins may play in the production of fetal abnormalities such as hydrocephalus, anencephalus, spina bifida, amputation of extremities, etc.? .And yet we have noted, as have many others9 ' 12 the higher incidence of such conditions in families with proved parental Rh incompatibility. Summary 1. A series of multiple pregnancies has been studied. 2. Six cases which clinically and serologically suggested Rh incompatibility have been investigated and discussed in detail. •Refers to Mendelian !!rroup In 1'able ! .
450
AMERICAK JOURNAL OF OBSTETRICS AKD GYKECOLOGY
References l. Stratton! F., Langley, F. A., and. Listel) U.: Brit. M .•J. 1 ~ 151-15~, 1945. ·> Aaburg, 1!. E.J and Roby, C.: A!\f. J. UBST. & GYNEC. 50: .J48, 194u. 3. Wiener! A. S.: .J . Lab. & Clin. Med. 30: 395! 661, 957, 1945.
4. Levine, Philip: Arch. Path. 37: 83-90! 1944. 5. Wiener, A. S., Wexler, I. B., and Gamrin, E.: Am. J. Dis. Child. 68: 317-323, HlH. 6. Personal communication. i. Guyer, Michael F.: Being Well-Born, Indianapolis, 1927, Bohbs-:Merril Co. 8. Levine, Pl1ilip: Human Fertil. 9: 65-72, 1944. AM. ,J. OBST. & GYNEC. 46: 827, 1943. fl. Schwartz, Harold A., and Levine, Philip: 10. \Yiener, A. S., Davidsohn, T., and Pottnr, E. L.: .r. Exper. :\fed. 81: 63-72, lfl±5. 11. Levine, Philip: West; .J. Surg. 50: 468-475, 1942. !2. Traut, H. 11'., Mcivor, B. C., Howard! J., Lucia, S. P., and Charvet, L.: ~~M. J. OBST. & GYKEC. 50: 722, 1945.