Pregnancy and Pseudopregnancy
- Sperm cells enter the oviducts within 25
seconds of breeding. They do however, need around 7 hours to
capacitate, before they are actually ready to fertilize. Sperm
cells can live up to 7 days within the bitch's uterus.
- Progesterone is produced by the corpora lutea
on the ovaries. The corpora lutea are the only source of
progesterone for the canine pregnancy.
- Therefore, the bitch needs ovaries for
progesterone production and maintaining pregnancy.
- A minimum of 2 ng/ml is needed to keep the
bitch pregnant. If progesterone falls below this
concentration, then the pregnancy will be lost.
- Progesterone is overall higher in pregnancy
than in diestrus, although the overlap in the concentrations
is too great to use as pregnancy diagnosis.
- Progesterone, after rising throughout estrus,
peaks at 35-40 ng/ml around 15-25 days of diestrus.
- Progesterone slowly declines during the
last week of pregnancy (or 1 week prepartum). During the last
week of pregnancy there is an abrupt decline in progesterone
- Prolactin is luteotrophic in the pregnant
bitch. It is needed to
maintain the corpora lutea (CLs), even though it is very low in the beginning
of diestrus. The prolactin concentration is inversely
related to the progesterone concentration. As progesterone
falls, prolactin rises. Therefore, prolactin rises starting at
midpregnancy. Prolactin is at a higher concentration in pregnant,
than nonpregnant bitches and higher in overt pseudopregnancy
than diestrus without overt pseudopregnancy.
- Dopamine is a prolactin
- Prolactin is detectable by day 20-30 of
pregnancy and peaks around days 40-50 of pregnancy.
- Relaxin is a pregnancy specific hormone that
comes from both the placenta and ovaries, however it is
primarily of placental origin.
- The packed cell volume decreases during
pregnancy because of hemodilution caused by an increase in
- The PCV is <40% at day 35 of pregnancy and
drops to <35% at term.
- The bitch is considered to have a variable
gestation length. This variability is mostly because of errors
in counting when conception occurred.
- If breeding dates are used to measure
gestation, then gestation can be as variable as 57-71 days.
This is because estrus is 9 days long and breeding can take
place during any day of estrus.
- The most accurate day to measure from is the
day of ovulation. In fact, gestation lasts 63 days from
ovulation. Ovulation is however, hard to determine in many
- If the LH peak is known, gestation can be
measured as lasting 65 days from the LH peak.
- Gestation can be accurately measured from the
first day of cytologic diestrus. Up to 80% of bitches whelp 57
days from the first day of cytologic diestrus. If behavioral
signs of the female rejecting the male are used to determine
the first day of diestrus, then gestation will be more
variable. This variability is can be 2-3 days different than
the first day of cytologic diestrus.
- Work done at LSU to
determine if litter size has an effect on gestation length.
Labrador Retrievers, German
Shepherd Dogs, Golden Retrievers
and hounds were more likely to
have a longer gestation
duration; three, four and nearly
eight times as likely,
Bitches with litters of four or
fewer pups are likely to have
longer gestation durations than
those with five or more pups.
- Induction of parturition has been
hypothesized to be similar to that of the sheep. In sheep it
is well established that a rise in fetal ACTH causes fetal to
cortisol increase. The fetal cortisol increase causes
placental prostaglandin release then causes placental
metabolism of progesterone to change to estrogen.
- Prostaglandins are produced near term in the
bitch and probably play a role in the induction of
Overt pseudopregnancy or pseudocyesis
- Each time a bitch enters estrus she is
designed to become pregnant, so she goes into a luteal 'pseudopregnancy
' every time she comes into estrus. For
learning sake, assume the hormonal events of pregnancy and
diestrus are the same, even though prolactin is lower in the
non-pregnant bitch. Prolactin
is higher in bitches that have overt psuedopregnancies as
compared to those that have covert pseudopregnancies. Diestrus
can be considered a covert pseudopregnancy. Overt
psuedopregnancy, or pseudocyesis or pseudogenetra occur in
- The signs of pseudogenetra (overt
psuedopregnancy, or pseudocyesis) include physical signs such
as mammary development and lactation; and psychological signs
such as nesting, mothering, and adopting inanimate objects.
Picture from a client. 'She
adopted these latex
chickens as her puppies.
I had to create a
"whelping box" for her
and the pups. She had
milk, was panting, not
eating, cried when a
"pup" squeaked, VERY
attentive to her litter,
etc. this lasted until
"weaning". So for
about 3-4 weeks we had
to live with this
madness!! It was almost
as bad as having a real
- Pseudogenetra occurs at the normal expected
Pseudogenetra rule outs
- The cause is the rapid decline in
progesterone at the end of a normal diestrus, coupled with a rise in prolactin (prolactin has been shown to be greater in
overtly pseudopregnant bitches than normal nonpregnant
- Other events that exacerbate the signs are
self nursing by the bitch, massage of the mammary glands by
the owner, hot packs of the mammary glands, and milking the
- Iatrogenic pseudogenetra can be caused by
ovariohysterectomy in diestrus. This results in a similar
progesterone decline as seen in the naturally occurring
- Progesterone supplementation during a
pseudogenetra will temporarily stop the signs, but the removal
of the progesterone will result in a recrudescence of the
- Parturition may have occurred somewhere, so
it is best to have done a pregnancy diagnosis at an earlier
time. Ultrasound of the uterus can help to determine if the
uterus is enlarged and the bitch may be postpartum.
- Mastitis and neoplasia are possibilities.
Ultrasound and radiographs can help rule these out.
- Benign mammary hypertrophy occurs mainly in
Sequelae to pseudogenetra,
- Not treating is best!!
- Remove all physical causes such as self nursing
by the bitch, massage of the mammary glands by the owner, hot
packs of the mammary glands, and milking the glands out.
- Non phenothiazine tranquilizers can be used
to calm the bitch. Phenothiazine tranquilizers can cause more
milk release because they are dopamine antagonists and
dopamine is a prolactin antagonist, so it will result in more
- Mibolerone is an androgen and has been shown to
improve 100% of the physical and 90% psychological signs when
administered at 0.016mg/kg for 5 days. It 'cured' 47% of the
physical and 77% of the psychological signs. It has become unavailable
again the US (8/2004).
- Bromocriptine (Parlodel) is a dopamine agonist, so it will
result in more dopamine, less prolactin, and less lactation.
Even though the prolactin is low in these bitches, it seems to
help. This may be because of the sensitivity to low
concentrations of prolactin. The
dose is 20 ug/kg for 8-10 days. Side effects include vomiting,
but this is apparently not as severe as some of the earlier
- Cabergoline (Dostinex) is also a dopamine
agonist. It has fewer side effects than bromocriptine. The dose
is 5 ug/kg SID for 5-10 days.
- Metergoline is a serotonin inhibitor and also
inhibits prolactin. The dose is 2 mg BID for 10 days. It may
cause whining and aggression. It is not available in the US.
- Estrogen and testosterone have been recommended
by some sources, but they are not advisable to use.
- Mammary hypertrophy
- Owner irritation.
- The good news is ovulation occurred, the
progesterone rise occurred, progesterone fall occurred...
everything worked !!!
- There is no predisposition to pyometra
resulting from pseudogenetra.