FOETAL FLUIDS IN CATTLE T. A. Bongso and P. K. Basrur*
cylinder, the volumes of fluid in amniotic and allantoic sacs were independently measured. The colour and consistency of the foetal fluids from each specimen were recorded. The age of each foetus was determined using crownrump length measurements (2) and developmental horizons for the bovine species (6). The gonadal sex of each foetus was also recorded.
INTRODUCTION BOVINE
FOETAL FLUID VOLUMES att
various
stages of gestation have been the subject of surprisingly few studies. The only thorough study in the bovine species was carried out by Arthur (1). In man however, detailed studies on the vdumes of amniotic fluid with gestation have been reported (4, 7, 8, 9). The normal volumes of foetal fluids in cattle have been used in the past to help the veterinarian in the diagnosis of diseases where excessive amounts of these fluids accumulate in their respective foetal compartments viz. hydrops amnii and hydrops allantois. More recently, the prenatal diagnosis of sex in cattle by amniocentesis was reported (3). Since a technique has been developed to aspirate bovine foetal fluids, diagnostic and therapeutic approaches to foetal pathology could be advanced in the near future. Hence, information on the amount of foetal fluids present at various stages of gestation will become of more than academic interest. This report concerns the volumes of bovine foetal fluids measured at various stages of gestation in Canadian Holstein cows. The purpose of measuring the volumes of the foetal fluids at different stages of gestation was primarily to find out the amount of both amniotic and allantoic fluid available in their respective sacs at the optimal time of amniocentesis viz. 70 to 100 days gestation, and to indicate whether the aspiration of 15 ml of foetal fluid at this time could result in abortion. It was also hoped that this study would throw more light on the shifts in volumes between the two foetal compartments with the trimesters as reported by Arthur (1).
RESULTS The data from 76 specimens revealed that the total volumes of amniotic and allantoic fluids increased progressively throughout gestation (Figure 1). A steep rise in the total volume occurred at about the 70th to 80th day of gestation. Although there was a steady increase of amniotic and allantoic fluids with gestation, the proportion of amniotic to allantoic fluid shifted through the trimesters. During the early part of the first trimester (0-76 days), allantoic fluid was in excess of amniotic fluid. From 76 days to 164 days (a greater part of the second trimester), amniotic fluid was greater in volume than allantoic fluid. During the latter part of the second trimester and through the third trimester (164 days to term), allantoic fluid was once again in excess of amniotic fluid (Figure 1). During the period at which amniocentesis could be performed (i.e. 70 to 100 days), amniotic and allantoic fluid volumes range from 150 to 1125 ml and 250 to 500 ml, respectively (Table I). There was a gradual shift in the colours of amniotic and allantoic fluids throughout gestation. Both amniotic and allantoic fluids were colourless from the 30th day up to the 100th day of gestation. Thereafter, throughout midpregnancy, both fluids were pale and resembled urine with a gradual increase in colour intensity as gestation advanced. Allantoic fluid became progressively more dark amber coloured throughout the third trimester. The colour of amniotic fluid, however, varied in the third trimester, the fluid generally being colourless. In rare instances, specimens exhibiting a dark amber, resembling allantoic fluid was also detected. Amniotic and allantoic fluid were of watery consistency throughout the first and second trimesters. As gestation advanced through the third trimester, the allantoic fluid became more
MATERIALS AND METHODS
Seventy-six pregnant reproductive tracts from Holstein cows, collected immediately after slaughter, were brought to the laboratory from the Schneider's abattoir, Kitchener, Ontaiio. The uterus of each specimen was carefully dissected and the foetal cotyledons unbuttoned from the maternal caruncles to display the amniotic and allantoic fluid compartments. Using a 100 ml syringe and 1000 ml graduated 'Department of Biomedical Sciences, Ontario
Veterinary College, University of Guelph, Guelph, Ontario NIG 2W2.
8 CAN. VET. JOUR., vol. 17, no. 2, February, 1976
FOETAL FLUIDS TOTAL A. ..*
FLUID
LLANTOIC
4-.-.-AMNIOTIC
FLUID
GESTATION (days)
FIGURE 1. Comparison of bovine foetal fluid volumes in normal pregnancies against stage of gestation. TABLE I FOETAL FLUID VOLUMES AT DIFFERENT STAGES OF GESTATION
CRL
Estimated age
(days)
Sex
1.9 2.5 3.8 5.1 6.4 7.0 7.6 8.9 11.4 12.1 12.7 15.2 17.2 17.8 19.1 21.6 25.4 26.7 27.9 31.8 35.6 38.1 40.6 44.5 48.3 50.8 53.3 58.4 62.2 71.7 76.2
30 38 45 53 60 62 66 72 78 79 81 90 94 96 98 105 113 117 120 130 132 140 150 158 167 171 180 188 195 210 225
FM MF MMF FFM MMF M MFF MF MFF M F FFM M F FMF FF MMF M FFM MFM FF MFM MMM MMF MFF FMF FFM MMM MFM FFM MMM
(cms)
Amniotic fluid (ml)
Allantoic fluid (ml)
Total
0.640.1
5444 9545
54.644 10747.5 155410 180±8
12±2.5 25±3 38±2
117i18 110
157±t26 150±10 348±10
440 525
548±13
975 1100
130±8
14247 208±422 210 255±29 260±20 278±7 300 300 307±17 375 425
977±15 1550±50 2125±38 2125 2217±30 3322±46 3025±25 2917±101 3000±116 3037±145 2567±291 3012±83 3042±464 3008±931
375±14 620±80 892±51 1350 1167±120 700±46 585± 15 1808±51 2050±116 2410±105 28504121 3910± 131 4033±578 5100±751 4683±303
2500±346
6575±983
30164390 27364433 39
55664318
(ml)
325440 320 412±55
410±30 627±17 740 825
855±30
1350 1525 1352429 2170± 130
3017±87
3475 33834249
4022±92 3610± 10 4725±152 5050±116 5447±240 54174312 6922±213 7075±+1042 810841682 7700±693 8303±751
9075±649
CANADIAN VETERINARY JOUflNAL
urine-like and the amniotic fluid changed to a highly viscous sticky fluid.
which the allantoic fluid volume predominates the amniotic fluid volume in the final trimester. It was postulated by Windle (10) that the formation of foetal fluid in animals of the order Artiodactyla that have separate amniotic and allantoic sacs was particularly complex. Urine from the bladder of the foetus could pass through the urachus into the allantoic sac or through the urethra into the amniotic sac. The results from the present report show that more of the foetal urine reaches the amniotic sac via the urethra between 76 to 164 days and this is reversed from 164 days onwards, with urine reaching the allantoic sac via the urachus. It is, therefore, obvious that at 164 days there is a marked control of the foetal urine into either sac. It is hypothesized that the cessation of drainage through the urethra into the amniotic sac at 164 days and onwards is due to the onset of function of the foetal bladder sphincter. Consequently, foetal urine flows passively via the urachus into the allantoic sac. Further, by this time, the swallowing reflexes of the foetus are well developed, the foetus thereby removing most of the amniotic fluid by deglutition. The amniotic fluid consistency being highly viscous towards term is possibly due to excessive salivary and alimentaiy tract secretions at a time when most of the foetal systems are well developed. The lubricant properties attributable to the amniotic fluid towards term is nature's device for easy passage of the foetus through the maternal birth canal at parturition. The closure of the urachus coincides with closure of the umbilical cord after parturition has taken place. The outlet of the foetal urinary bladder is now limited to only the urethra when the adult function of micturition begins.
DISCUSSION It has been shown from the results in this study that the proportion of amniotic to allantoic fluid shifts through the trimesters. Between 76 and 164 days of gestation, bovine amniotic fluid was in excess of allantoic fluid. These results are consistent with those reported by Arthur (1) who showed that amniotic fluid predominated allantoic fluid between 80 and 175 days of gestation. At the optimal time for amniocentesis in the bovine (i.e. 70 to 100 days), amniotic and allantoic fluid volumes ranged from 150 to 1125 ml and 250 to 500 ml, respectively. In the case of man, transabdominal amniocentesis could be performed from 14 weeks onwards. From 15 weeks, the volume of amniotic fluid increases by about 50 ml per week up to about 28 weeks (4). Hence, during the period at which human amniocentesis is usually performed (98 to 154 days), amniotic fluid volumes range from 125 ml to 475 ml. A comparison of bovine and human foetal fluid volumes during the optimal time for amniocentesis shows that those of cattle are far in excess to those of man. Withdrawal of up to 20 ml of human amniotic fluid during amniocentesis does not have any harmful effect on foetal development (5). Hence, the aspiration of 15 ml of foetal fluid during transvaginal amniocentesis in the bovine should in no way be a hazard to the foetus. Fuchs (5) commented that replacement of the aspirated amniotic fluid with a similar volume of physiological saline in man, was not necessary. Since in the bovine species the technique of amniocentesis is transvaginal, care must be taken not to introduce micro-organisms into the foetal cavities if saline replacement is to be perSUMMARY formed. The results of field trials show that The volume, colour and consistency of the replacement with saline is not necessary if up to 15 ml of foetal fluid is withdrawn amniotic and allantoic fluids were indepen(Bongso and Basrur - unpublished data). dently recorded from 76 pregnant uteri beIt is possible to consistently aspirate either longing to the Canadian Holstein breed. The amniotic or allantoic fluid during transvaginal gestational ages of the specimens ranged from amniocentesis (Bongso and Basrur - unpub- 30 to 225 days. Although the total fluid volume lished data). Confirmation as to which fluid increased progressively throughout pregnancy, has been aspirated could be carried out on the proportion of allantoic to amniotic fluid the basis of the types of cells present and from shifted through the trimesters. During the early the colour and consistency of the fluids. part of the first trimester (0-76 days) allantoic As gestation advanced from 165 days on- fluid was in excess of amniotic fluid. From 76 wards, the allantoic fluid became dark amber to 164 days (a greater part of the second coloured and urine-like while the amniotic fluid trimester), amniotic fluid was greater in volume underwent a change to a colourless, highly than allantoic fluid. During the latter part of viscous fluid. The time at which these changes the second trimester and through the third begin to appear corresponds with the time at trimester (164 days to term), allantoic fluid 40
FOETAL FLUIDS
was once again in excess of amniotic fluid. At the optimal time for transvaginal amniocentesis in the bovine (i.e. 70 to 100 days), amniotic and allantoic fluid volumes range from 150 to 1125 ml and 250 to 500 ml, respectively.
and Fellowship Agency and the financial support for this project from the Ontario Ministry of Agriculture and Food are gratefully acknowledged. 1.
REsuME
Cette experience visait 'a determiner la quantite, la couleur et la consistance des liquides amniotique et allantoidien de 76 uterus gravides provenant de vaches Holstein. Les echantillonnages s'echelonnerent entre le 30e et le 225e jour de la gestation. En depit d'une augmentation progressive de ces liquides au cours de la gestation, la proportion entre les deux varia d'un trimestre a l'autre. Au debut du premier (0-76 jours), la quantite du liquide allantoidien excedait celle du liquide amniotique. Dans la majeure partie du second trimestre (76-164 jours), le contraire se produisit. Vers la fin du second trimestre et durant tout le troisieme (164 jours-terme), la quantite du liquide allantoidien depassa de nouveau celle du liquide amniotique. Au temps ideal pour l'amniocentese trans-vaginale chez la vache, c'est-a-dire du 70e au 100e jour de gestation, la quantite des liquides amniotique et allantoidien variait respectivement de 150 a 1125 ml et de 250 a 500 ml. ACKNOWLEDGMENTS The authors are greatly indebted to Mr. Craig Underhill and J. M. Schneider Meat Packers, Kitchener, Ontario for their help and cooperation in this work. The scholarship to the senior author from the Canadian Commonwealth Scholarship
41
2.
3. 4.
5.
6.
7. 8.
9.
10.
REFERENCES ARTHUR, G. H. Some notes on the quantities of foetal fluids in ruminants with special reference to Hydrops amnii. Br. vet. J. 113: 17-28. 1957. ARTHUR, G. H. Wright's Veterinary Obstetrics. Edition 3. pp. 60-82. London: Bailliere, Tindall and Cox Ltd. 1964. BONGSO, T. A. and P. K. BASRUR. Prenatal diagnosis of sex in cattle by amniocentesis. Vet. Rec. 96: 124-127. 1975. FUCHS, F. Volume of amniotic fluid at various stages of pregnancy. Clin. Obs. Gyn. 9: 449-460. 1966. FUCHS, F. Amniocentesis: techniques and complications. In Early Diagnosis of Human Genetic Defects. M. Harris, Editor. pp. 11-16. Washington: U.S. Government Printing Office. 1970. HAFEZ, E. S. E. and M. R. JAINUDEEN. Gestation, prenatal physiology and parturition. In Reproduction in Farm Animals. E. S. E. Hafez, Editor. pp. 166-202. Philadelphia: Lea and Febiger. 1974. HASWELL, G. L. and J. A. MORRIS. Amniotic fluid volume studies. Obs. Gyn. 42: 725-732. 1973. QUEENAN, J. T., W. THOMPSON, C. R. WHITFIELD and S. I. SHAH. Amniotic fluid volumes in normal pregnancies. Am. J. Obs. Gyn. 114: 34-38. 1972. WAGNER, G. and F. FUCHS. Volume of amniotic fluid in the first half of human pregnancy. J. Obs. Gyn. Br. Comm. 69: 131-133. 1962. WINDLE, W. F. The Physiology of the Foetus. Philadelphia: W. B. Saunders Co. 1940.
cylinder, the volumes of fluid in amniotic and allantoic sacs were independently measured. The colour and consistency of the foetal fluids from each specimen were recorded. The age of each foetus was determined using crownrump length measurements (2) and developmental horizons for the bovine species (6). The gonadal sex of each foetus was also recorded.
INTRODUCTION BOVINE
FOETAL FLUID VOLUMES att
various
stages of gestation have been the subject of surprisingly few studies. The only thorough study in the bovine species was carried out by Arthur (1). In man however, detailed studies on the vdumes of amniotic fluid with gestation have been reported (4, 7, 8, 9). The normal volumes of foetal fluids in cattle have been used in the past to help the veterinarian in the diagnosis of diseases where excessive amounts of these fluids accumulate in their respective foetal compartments viz. hydrops amnii and hydrops allantois. More recently, the prenatal diagnosis of sex in cattle by amniocentesis was reported (3). Since a technique has been developed to aspirate bovine foetal fluids, diagnostic and therapeutic approaches to foetal pathology could be advanced in the near future. Hence, information on the amount of foetal fluids present at various stages of gestation will become of more than academic interest. This report concerns the volumes of bovine foetal fluids measured at various stages of gestation in Canadian Holstein cows. The purpose of measuring the volumes of the foetal fluids at different stages of gestation was primarily to find out the amount of both amniotic and allantoic fluid available in their respective sacs at the optimal time of amniocentesis viz. 70 to 100 days gestation, and to indicate whether the aspiration of 15 ml of foetal fluid at this time could result in abortion. It was also hoped that this study would throw more light on the shifts in volumes between the two foetal compartments with the trimesters as reported by Arthur (1).
RESULTS The data from 76 specimens revealed that the total volumes of amniotic and allantoic fluids increased progressively throughout gestation (Figure 1). A steep rise in the total volume occurred at about the 70th to 80th day of gestation. Although there was a steady increase of amniotic and allantoic fluids with gestation, the proportion of amniotic to allantoic fluid shifted through the trimesters. During the early part of the first trimester (0-76 days), allantoic fluid was in excess of amniotic fluid. From 76 days to 164 days (a greater part of the second trimester), amniotic fluid was greater in volume than allantoic fluid. During the latter part of the second trimester and through the third trimester (164 days to term), allantoic fluid was once again in excess of amniotic fluid (Figure 1). During the period at which amniocentesis could be performed (i.e. 70 to 100 days), amniotic and allantoic fluid volumes range from 150 to 1125 ml and 250 to 500 ml, respectively (Table I). There was a gradual shift in the colours of amniotic and allantoic fluids throughout gestation. Both amniotic and allantoic fluids were colourless from the 30th day up to the 100th day of gestation. Thereafter, throughout midpregnancy, both fluids were pale and resembled urine with a gradual increase in colour intensity as gestation advanced. Allantoic fluid became progressively more dark amber coloured throughout the third trimester. The colour of amniotic fluid, however, varied in the third trimester, the fluid generally being colourless. In rare instances, specimens exhibiting a dark amber, resembling allantoic fluid was also detected. Amniotic and allantoic fluid were of watery consistency throughout the first and second trimesters. As gestation advanced through the third trimester, the allantoic fluid became more
MATERIALS AND METHODS
Seventy-six pregnant reproductive tracts from Holstein cows, collected immediately after slaughter, were brought to the laboratory from the Schneider's abattoir, Kitchener, Ontaiio. The uterus of each specimen was carefully dissected and the foetal cotyledons unbuttoned from the maternal caruncles to display the amniotic and allantoic fluid compartments. Using a 100 ml syringe and 1000 ml graduated 'Department of Biomedical Sciences, Ontario
Veterinary College, University of Guelph, Guelph, Ontario NIG 2W2.
8 CAN. VET. JOUR., vol. 17, no. 2, February, 1976
FOETAL FLUIDS TOTAL A. ..*
FLUID
LLANTOIC
4-.-.-AMNIOTIC
FLUID
GESTATION (days)
FIGURE 1. Comparison of bovine foetal fluid volumes in normal pregnancies against stage of gestation. TABLE I FOETAL FLUID VOLUMES AT DIFFERENT STAGES OF GESTATION
CRL
Estimated age
(days)
Sex
1.9 2.5 3.8 5.1 6.4 7.0 7.6 8.9 11.4 12.1 12.7 15.2 17.2 17.8 19.1 21.6 25.4 26.7 27.9 31.8 35.6 38.1 40.6 44.5 48.3 50.8 53.3 58.4 62.2 71.7 76.2
30 38 45 53 60 62 66 72 78 79 81 90 94 96 98 105 113 117 120 130 132 140 150 158 167 171 180 188 195 210 225
FM MF MMF FFM MMF M MFF MF MFF M F FFM M F FMF FF MMF M FFM MFM FF MFM MMM MMF MFF FMF FFM MMM MFM FFM MMM
(cms)
Amniotic fluid (ml)
Allantoic fluid (ml)
Total
0.640.1
5444 9545
54.644 10747.5 155410 180±8
12±2.5 25±3 38±2
117i18 110
157±t26 150±10 348±10
440 525
548±13
975 1100
130±8
14247 208±422 210 255±29 260±20 278±7 300 300 307±17 375 425
977±15 1550±50 2125±38 2125 2217±30 3322±46 3025±25 2917±101 3000±116 3037±145 2567±291 3012±83 3042±464 3008±931
375±14 620±80 892±51 1350 1167±120 700±46 585± 15 1808±51 2050±116 2410±105 28504121 3910± 131 4033±578 5100±751 4683±303
2500±346
6575±983
30164390 27364433 39
55664318
(ml)
325440 320 412±55
410±30 627±17 740 825
855±30
1350 1525 1352429 2170± 130
3017±87
3475 33834249
4022±92 3610± 10 4725±152 5050±116 5447±240 54174312 6922±213 7075±+1042 810841682 7700±693 8303±751
9075±649
CANADIAN VETERINARY JOUflNAL
urine-like and the amniotic fluid changed to a highly viscous sticky fluid.
which the allantoic fluid volume predominates the amniotic fluid volume in the final trimester. It was postulated by Windle (10) that the formation of foetal fluid in animals of the order Artiodactyla that have separate amniotic and allantoic sacs was particularly complex. Urine from the bladder of the foetus could pass through the urachus into the allantoic sac or through the urethra into the amniotic sac. The results from the present report show that more of the foetal urine reaches the amniotic sac via the urethra between 76 to 164 days and this is reversed from 164 days onwards, with urine reaching the allantoic sac via the urachus. It is, therefore, obvious that at 164 days there is a marked control of the foetal urine into either sac. It is hypothesized that the cessation of drainage through the urethra into the amniotic sac at 164 days and onwards is due to the onset of function of the foetal bladder sphincter. Consequently, foetal urine flows passively via the urachus into the allantoic sac. Further, by this time, the swallowing reflexes of the foetus are well developed, the foetus thereby removing most of the amniotic fluid by deglutition. The amniotic fluid consistency being highly viscous towards term is possibly due to excessive salivary and alimentaiy tract secretions at a time when most of the foetal systems are well developed. The lubricant properties attributable to the amniotic fluid towards term is nature's device for easy passage of the foetus through the maternal birth canal at parturition. The closure of the urachus coincides with closure of the umbilical cord after parturition has taken place. The outlet of the foetal urinary bladder is now limited to only the urethra when the adult function of micturition begins.
DISCUSSION It has been shown from the results in this study that the proportion of amniotic to allantoic fluid shifts through the trimesters. Between 76 and 164 days of gestation, bovine amniotic fluid was in excess of allantoic fluid. These results are consistent with those reported by Arthur (1) who showed that amniotic fluid predominated allantoic fluid between 80 and 175 days of gestation. At the optimal time for amniocentesis in the bovine (i.e. 70 to 100 days), amniotic and allantoic fluid volumes ranged from 150 to 1125 ml and 250 to 500 ml, respectively. In the case of man, transabdominal amniocentesis could be performed from 14 weeks onwards. From 15 weeks, the volume of amniotic fluid increases by about 50 ml per week up to about 28 weeks (4). Hence, during the period at which human amniocentesis is usually performed (98 to 154 days), amniotic fluid volumes range from 125 ml to 475 ml. A comparison of bovine and human foetal fluid volumes during the optimal time for amniocentesis shows that those of cattle are far in excess to those of man. Withdrawal of up to 20 ml of human amniotic fluid during amniocentesis does not have any harmful effect on foetal development (5). Hence, the aspiration of 15 ml of foetal fluid during transvaginal amniocentesis in the bovine should in no way be a hazard to the foetus. Fuchs (5) commented that replacement of the aspirated amniotic fluid with a similar volume of physiological saline in man, was not necessary. Since in the bovine species the technique of amniocentesis is transvaginal, care must be taken not to introduce micro-organisms into the foetal cavities if saline replacement is to be perSUMMARY formed. The results of field trials show that The volume, colour and consistency of the replacement with saline is not necessary if up to 15 ml of foetal fluid is withdrawn amniotic and allantoic fluids were indepen(Bongso and Basrur - unpublished data). dently recorded from 76 pregnant uteri beIt is possible to consistently aspirate either longing to the Canadian Holstein breed. The amniotic or allantoic fluid during transvaginal gestational ages of the specimens ranged from amniocentesis (Bongso and Basrur - unpub- 30 to 225 days. Although the total fluid volume lished data). Confirmation as to which fluid increased progressively throughout pregnancy, has been aspirated could be carried out on the proportion of allantoic to amniotic fluid the basis of the types of cells present and from shifted through the trimesters. During the early the colour and consistency of the fluids. part of the first trimester (0-76 days) allantoic As gestation advanced from 165 days on- fluid was in excess of amniotic fluid. From 76 wards, the allantoic fluid became dark amber to 164 days (a greater part of the second coloured and urine-like while the amniotic fluid trimester), amniotic fluid was greater in volume underwent a change to a colourless, highly than allantoic fluid. During the latter part of viscous fluid. The time at which these changes the second trimester and through the third begin to appear corresponds with the time at trimester (164 days to term), allantoic fluid 40
FOETAL FLUIDS
was once again in excess of amniotic fluid. At the optimal time for transvaginal amniocentesis in the bovine (i.e. 70 to 100 days), amniotic and allantoic fluid volumes range from 150 to 1125 ml and 250 to 500 ml, respectively.
and Fellowship Agency and the financial support for this project from the Ontario Ministry of Agriculture and Food are gratefully acknowledged. 1.
REsuME
Cette experience visait 'a determiner la quantite, la couleur et la consistance des liquides amniotique et allantoidien de 76 uterus gravides provenant de vaches Holstein. Les echantillonnages s'echelonnerent entre le 30e et le 225e jour de la gestation. En depit d'une augmentation progressive de ces liquides au cours de la gestation, la proportion entre les deux varia d'un trimestre a l'autre. Au debut du premier (0-76 jours), la quantite du liquide allantoidien excedait celle du liquide amniotique. Dans la majeure partie du second trimestre (76-164 jours), le contraire se produisit. Vers la fin du second trimestre et durant tout le troisieme (164 jours-terme), la quantite du liquide allantoidien depassa de nouveau celle du liquide amniotique. Au temps ideal pour l'amniocentese trans-vaginale chez la vache, c'est-a-dire du 70e au 100e jour de gestation, la quantite des liquides amniotique et allantoidien variait respectivement de 150 a 1125 ml et de 250 a 500 ml. ACKNOWLEDGMENTS The authors are greatly indebted to Mr. Craig Underhill and J. M. Schneider Meat Packers, Kitchener, Ontario for their help and cooperation in this work. The scholarship to the senior author from the Canadian Commonwealth Scholarship
41
2.
3. 4.
5.
6.
7. 8.
9.
10.
REFERENCES ARTHUR, G. H. Some notes on the quantities of foetal fluids in ruminants with special reference to Hydrops amnii. Br. vet. J. 113: 17-28. 1957. ARTHUR, G. H. Wright's Veterinary Obstetrics. Edition 3. pp. 60-82. London: Bailliere, Tindall and Cox Ltd. 1964. BONGSO, T. A. and P. K. BASRUR. Prenatal diagnosis of sex in cattle by amniocentesis. Vet. Rec. 96: 124-127. 1975. FUCHS, F. Volume of amniotic fluid at various stages of pregnancy. Clin. Obs. Gyn. 9: 449-460. 1966. FUCHS, F. Amniocentesis: techniques and complications. In Early Diagnosis of Human Genetic Defects. M. Harris, Editor. pp. 11-16. Washington: U.S. Government Printing Office. 1970. HAFEZ, E. S. E. and M. R. JAINUDEEN. Gestation, prenatal physiology and parturition. In Reproduction in Farm Animals. E. S. E. Hafez, Editor. pp. 166-202. Philadelphia: Lea and Febiger. 1974. HASWELL, G. L. and J. A. MORRIS. Amniotic fluid volume studies. Obs. Gyn. 42: 725-732. 1973. QUEENAN, J. T., W. THOMPSON, C. R. WHITFIELD and S. I. SHAH. Amniotic fluid volumes in normal pregnancies. Am. J. Obs. Gyn. 114: 34-38. 1972. WAGNER, G. and F. FUCHS. Volume of amniotic fluid in the first half of human pregnancy. J. Obs. Gyn. Br. Comm. 69: 131-133. 1962. WINDLE, W. F. The Physiology of the Foetus. Philadelphia: W. B. Saunders Co. 1940.
