Celhaus Guide to Puppy
Development in Utero
(researched by Cel Hope of Celhaus GSDs, thank you Cel
for letting my share this)
A Litter vom Wenner Haus, due February 18, 2013
Day 1 (Day of Mating) December
17 Sperm
migrate up the vagina and through the cervix (entrance
to the uterus). They can live inside the bitch up to 7
days.
Days 2-3
December
18-19 Sperm
continue to travel looking for mature eggs, eventually
finding them in the oviducts (passages from the ovaries
to the uterus). Fertilization occurs in the oviducts.
Days 4-8 December
20-21
Fertilized eggs move down the oviducts and into the
horns of the uterus, rapidly developing all the while.
Each fertilized egg divides to form a 2-celled organism,
then again to form a 4 celled organism, 16 celled, and
so forth. Once the fertilized egg begins to divide, it
is called a blastocyst.
Days 14-19
December 31- January 5 By
day 14 they’re in the 64-cell stage. They continue to
grow and divide. By day 19 they are large and complex
enough to be classified as embryos.
Days 22-28
January 8-14
The embryos attach to the wall of the uterus, spacing
out so that each pup has room to develop. The face,
eyes and spinal column develop. Injury or chemicals at
this stage can cause deformed embryos.
In some breeds, pregnancy can be verified by
palpation during Days 26-32, but I've never had any luck
with my German Shepherds because their bodies are so
deep and muscular.
A blood test can confirm pregnancy by evaluating the
amount of the pregnancy-specific hormone Relaxin, which
comes from both the uterus and placenta (mainly from the
placenta) only when the embryos attach to the wall of
the uterus (about 22-27 days after breeding). False
negative readings are possible close to the 22 day mark
but if repeated at about age 28 in a pregnant bitch will
read positive, so I never do the Relaxin test on my
bitches before they’re 4 weeks in whelp. Then,
generally, they’re showing physical signs anyway, so I
only do the test when it’s important to know beyond the
shadow of a doubt that the bitch is pregnant (such as
needing to know whether or not to enter her in shows,
since entries must be made a month or two in advance of
the show date).
28 days after breeding, an ultrasound will show fetuses,
and more importantly, fetal heartbeats. The heartbeats
let you know you have live, developing puppies. The
bitch is held on her back on an exam table, the hair on
her belly is shaved, lubricant is applied and a probe
connected to a TV-like screen is pressed firmly against
her skin and moved around. The pups are recognizable as
puppies and fascinating to watch as they move around and
their hearts beat away. Still photos of the pups in
utero can be taken. The uterus has two horns, with
puppies implanted and developing in each horn. On an
ultrasound, which cannot go deep enough to see both
horns simultaneously, it’s impossible to see all puppies
at once. The ultrasound can only show part of the uterus
at a time, so it’s easy to count one puppy several
times, thinking you have moved to a different part of
the uterus when you actually have just changed
angles—and to miss other puppies altogether.
Days 29 - 35 January
15-21
Toes, claws and whiskers develop, and the fetuses
lengthen and begin to look like dogs. Gender is
detectable. By the end of this week the fetuses are no
longer vulnerable to chemicals.
Days 36-42
January
22-28 Heartbeats
can be heard with a stethoscope. Skin pigment develops.
Days 50-56
February 5-11 the
pups are developing fast and beginning to take up more
and more room, so the pregnancy begins to be obvious.
They don’t fit under the bitch’s rib cage any more so
her abdomen distends. It’s usually obvious when they
“drop” into the abdomen as they begin to migrate closer
to the birth passage. Since some of the pups are
resting in the abdomen below the ribcage, they can often
be seen moving and kicking when she sleeps stretched out
on her side. You can sit beside her and gently hold
your palm against her abdomen and feel the babies move.
Since the pup’s skeletons are now formed, radiographs
can be taken and the number of pups counted. I know
approximately how many to expect. So if the bitch quits
whelping before she should, I know she could be in
trouble and can call the vet, get help, and hopefully
save lives.
Days 59-66
February
15-21 the
pups should be born during this period.
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