Canine Prenatal Development

Rebecca Dablow, CVT
Associate Veterinary Information Specialist 

Over the past few months, many of my friends have had new puppies introduced into their families.  A few weeks ago, my coworker and Pet Poison Helpline’s own Tasha G., CVT assisted her dog give birth to 15 healthy puppies!  Following all of this, I watched a continuing education talk on reproduction by our own Dr. Sarah Alpert.

This got me thinking about… puppies!  More specifically, puppy development before birth, in the womb.  Today I’d like to talk about canine prenatal development.  It is truly fascinating to learn about what happens in those short 63 days before birth.  This is just a short synopsis of the many intricate changes that occur when puppies begin to develop from a tiny fertilized egg.

Within about 2 weeks of conception, newly fertilized embryos attach to their mother’s uterus. From here, the puppies begin to develop.  A tiny-puppy heart is beating at 22-23 days post conception!  They will rely solely on their mom before birth for nutrients via the umbilical cord.  They each have their own amniotic sac–the fluid filled “bag” which will surround them and protect them during their development.

Mom will not appear pregnant quite yet, but her body will be going through many changes at this time and she will benefit from some extra love and TLC.  Around week 3, she may even develop some nausea and vomiting as her hormones fluctuate.  This is usually very mild and short-lived for dogs.   We would want her evaluated if she loses her appetite or vomits persistently. Mom’s mammary chains may also swell slightly and become darker in color in preparation for nursing.

At approximately 4 weeks, we are about halfway through pregnancy. Ultrasound is typically accurate to confirm pregnancy now. Ossification (the hardening and development of bone) begins to take place. We can consider snapping an abdominal X-ray around days 43-50. We can often count the developing spines of the dogs at this time to aid in determining the size of the litter. This is extremely helpful as we will then know exactly what to expect for when gives birth.

The puppies’ muscular systems, organs, haircoat and whiskers are becoming more evident in the following weeks.  The eyes and little facial features are developing!  Unlike humans, the puppies’ eyes remain closed until a few weeks after birth.  They are sexually dimorphic at this time, but their genders will be very difficult to determine until they are born.

Over the 4 to 6 week mark, the mother will start to become much more visibly pregnant as the puppies increase in size.  She may need to eat more frequently and in smaller amounts as her stomach is becoming more compressed with the uterus enlarging.  Ask your veterinarian what she should be receiving as far as diet to ensure all her nutrient needs are met.

Toward the end of pregnancy (6-8+ weeks, or about 63 days average), You’ll notice mom may begin ‘nesting’, or appear busy and agitated as she prepares and plans for the perfect spot to deliver.  You may also see some colostrum (the first milk) leaking from her nipples.  In the 48 hours before birth, mom will typically undergo a body temperature drop by a few degrees.  Many breeders will use this as a sign that labor is likely to begin soon.

The majority of dogs don’t need any physical assistance during delivery and do just fine managing on their own.  There are some breeds, such as bulldogs, who usually require a Caesarian procedure or other emergency assistance.  Most puppies will be born within 2 hours of each other with some variation.  If mom has gone longer than this time frame, is straining with no puppy production, or appears in distress, contact your emergency veterinarian immediately.

Tasha G, CVT’s recent litter, born 10/26/18.  15 puppies is quite remarkable!