DROPSY OF THE FETAL MEMBRANES AND FETUS:
Three dropsical conditions of the conceptus may be seen in veterinary obstetrics: oedema
of the placenta, dropsy of the fetal sacs and dropsy of the fetus. They may occur
separately or in combination.
Oedema of the placenta:
This frequently accompanies a placentitis: for example, Brucella abortus infection in
cattle. It doesnot cause dystocia but is frequently associated with abortion or stillbirth.
Dropsy of the fetal sacs
Both the amniotic and allantoic sacs can contain excessive quantities of fetal fluid. When
this occurs it is referred to as hydramnios or hydrallantois, depending on which sac is
involved. Hydrallantois is much more common than hydramnios, although the latter is
always seen in association with specific fetal abnormalities such as the ‘bulldog’ calf in
the Dexter. A few cases have been recorded in sheep, associated with
Either twins or triplets, in which the excess of fluid – amounting to about 18.5 litres –
was in the amniotic sac. It has also been reported in the dog involving all fetuses in a
litter. Apart from the hereditary cases of
hydramnios which accompany the Dexter
‘bulldog’ calf, and which may occur as early as
the third or fourth month, most instances of
dropsy of the fetal sacs of cattle are seen in the
last 3 months of gestation. The cause is not
known.
Histologically,
there
was
a
noninfectious degeneration and necrosis of the
endometrium and, as already observed, the fetus
was undersized. Normally, in cattle, there is a markedly accelerated production of
allantoic fluid at 6–7 months of gestation, and it is suggested that, where placental
dysfunction exists, this increase may become uncontrolled and lead to massive
accumulation. It is also frequently associated with twins. All cases of hydrallantois are
progressive, but they vary in time of clinical onset (within the last 3 months of
pregnancy) and in their rate of progression. The essential symptom is distension of the
abdomen by the excess of fetal fluid. The later in gestation the condition occurs, the more
likely it is that the cow will survive to term, whereas if the abdomen is obviously
distended at 6 or 7 months, the cow will become extremely ill long before term. The
volume of allantoic fluid varies up to 273 litres, and such large amounts impose a serious
strain on the cow and greatly hamper respiration and reduce appetite. There is gradual
loss of condition, eventually causing recumbency and death. Occasionally, the animal
becomes relieved by aborting. The less severely affected reach term in poor condition
and, because of uterine inertia (often accompanied by incomplete dilation of the cervix),
frequently require help at parturition.
The diagnosis of bovine hydrallantois is based on the easily appreciable fluid distension
of the abdomen, with its associated symptoms, in the last third of pregnancy.
Confirmation may be obtained by the rectal palpation of the markedly swollen uterus and
by the failure to palpate the fetus either per rectum or externally.
The treatment of hydrallantois calls for a realistic approach and a nicety of judgment.
Cases that have become recumbent should be slaughtered. Where the animal is near term,
a one- or two-stage caesarean operation is indicated. With both methods it is imperative
that the fluid is allowed to escape slowly, so as to prevent the occurrence of
hypovolaemic shock associated with splanchnic pooling of blood. Since hydrallantois is
frequently seen in twin pregnancies in cows, it is particularly important to search the
grossly distended uterus for the second calf. Cases of hydrallantois which calve, or are
delivered by caesarian operation, frequently retain the placenta and, owing to tardy
uterine involution, often develop metritis. This may lead to a protracted convalescence
and delayed conception. By using a synthetic corticosteroid (dexamethasone or
flumethasone) in conjunction with oxytocin, improved therapy for hydrallantois. About 4
or 5 days after an injection of 20 mg of dexamethasone or 5–10 mg of flumethasone the
cervix relaxes and the cow is given oxytocin by means of an intravenous drip for 30
minutes. Of 20 cows so treated, 17 recovered.
Dropsy of the fetus
There are several types of fetal dropsy, and those of obstetric importance are
hydrocephalus, ascites and anasarca.
Hydrocephalus
Hydrocephalus involves a swelling of the cranium due to an accumulation of fluid which
may be in the ventricular system or between the brain and the dura. It affects all species
of animals and is seen most commonly by veterinary obstetricians in pigs,
puppies and calves. In the more severe forms of hydrocephalus there is marked thinning
of the cranial bones. This facilitates trocarisation and compression of the skull so as to
allow vaginal delivery. Where this cannot be done, the dome of the cranium may be sawn
off with fetotomy wire or a chain saw. If the fetus is decapitated there is still the difficulty
of delivering the head. Caesarean section may be performed, but there is no merit in
obtaining a live hydrocephalic calf; however, this operation, may be necessary in severe
cases affecting pigs and dogs, and in cattle when the calf is presented posteriorly or when
hydrocephalus is accompanied by ankylosis of the limb joints.
Fetal ascites
Dropsy of the peritoneum is a common accompaniment of infectious disease of the fetus
and of developmental defects, such as achondroplasia. Occasionally, it occurs as the only
defect. Aborted fetuses are often dropsical; when the fetus is full-term, ascites may cause
dystocia. This can usually be relieved by incising the fetal abdomen with a fetotomy
knife.
Fetal anasarca
The affected fetus is usually carried to term, and concern is caused by the lack of
progress in second-stage labour. This is due to the great increase in fetal volume caused
by the excess of fluid in the subcutaneous tissues, particularly of the head and hind limbs.
In the case of the head, there is so much swelling that the normal features are masked and
the resultant appearance is quite grotesque. It is an interesting point that an undue
proportion of these anasarcous fetuses are presented posteriorly, in which case the
enormous swelling of the presenting limbs is very conspicuous. There is frequently an
excess of fluid in the peritoneal and pleural cavities with dilatation of the umbilical and
inguinal rings as well as hydrocoele. The substance of the fetal membranes is also
oedematous and occasionally there is a degree of hydrallantois.
SUPERFECUNDATION
Superfecundation is the condition in which offspring from two sires are conceived
c2ontemporaneously. Owing to the number of ova shed and their longevity, as well as to
the length of oestrus and the promiscuous mating behaviour of the species,
superfecundation is most likely in the bitch. The phenomenon is suspected when mating
to two dogs of different breeds is known to have occurred, and the suspicion is
heightened when the litter shows marked dual variation in color pattern, conformation
and size. Superfecundation has been reported when a mare gave birth to twin horse and
mule foals, and when a Friesian cow delivered twin Friesian and Hereford calves.
SUPERFETATION
Superfetation is the condition that arises when an animal already pregnant mates,
ovulates and conceives a second fetus or second litter. It is not uncommon for a cow to be
mated when pregnant, but no evidence is available that ovulation occurs in a cow
carrying a live fetus. Ovulation does occur in pregnant mares, and in this species
superfetation is theoretically possible. Superfetation is suspected when fetuses of very
different size are born together or when two fetuses, or two litters, are born at widely
separated times. Apparently authentic cases have been described in which two normally
mature fetuses, or litters, have been delivered at times corresponding in gestation length
to two widely separated and observed matings.
Prolapse of the vagina and cervix (CVP):