The Reproductive Anatomy of the female Dog

The Mammary glands:

Female dogs (correctly called bitches) have 3,4 or 5 pairs of breasts(mammary glands) placed in two rows running up the sides of their abdomen from the groin to the chest for nursing puppies. The number varies and one side can have one or two more than the other side. The nipples on a female who has not yet had her firat "heat" are quite small, but they swell with the first"heat" and never return to 'puppy size'. If the bitch has been bred and is pregnant, then about 35 days after the mating the nipples will turn a deep pink color and will begin to enlarge. The mammary glands produce the milk to feed the puppies and amazingly enough they manage to manufacture the right supply to meet the demand. Bitches who are extremely maternal have been known to produce milk for a starving pup or another animal baby even though they are not pregnant or nusing their own litter.

The Vagina;

The vagina opening is quite small on a puppy too, and enlarges with the onset of the heat and never returns to "puppy size", but it does decrease in size after the heat is finished. The vagina inside the dog is NOT a straight tube. The first 1-2 inches of the vagina(depending on the size of the dog) is at a 45 degree upward angle and then it levels out and runs about another 3-4 inches ending at the 'cervix'-the bottom end of the uterus. Also, inside the vagina, partway up, is the opening to the bladder- the tiny urethral opening, which allows the urine to run out of the vagina. Inside the vagina, as well, is very strong ring of muscles, placed at about where the angle of the vagina changes. These muscles have a purpose.

The uterus in the female dog is not like a human uterus which is pear shaped. The dogs uterus is Y shaped. The based of the Y is the cervix, which is usually tightly closed to prevent infections from getting into the uterus. It opens for the birthing of puppies. The two arms of the Y is where the whelps(puppies) develop, each in its own individual compartment. The 2 fallopian tubes sort a dangle over from the top of each arm of the Y and are each attached to the 2 oviers where the eggs are made and then released to the fallopian tubes when the egg is mature. The eggs are not released all at once by the ovary to the fallopian tube. Bitches are mulitple ovulators, which means that they make several eggs, and release them over a period of several hours, or even a day or so. It is the bitch who determines the number of puppies to be born. The male determines the sex of the puppy. The ovaries not onlymake eggs, they also produce the estrogen and the progesterone hormones.

The "Heat" cycle

The "Heat" cycle:

The female dog usually comes into"heat" or is "in season" every 6 months. The entire "Heat" period lasts an average of 21 days, but this may vary with some dogs. The actual "breeding time' is only a matter of 2 or 3 days in the 3 week period, but this time can be very difficult to determine.


The symptoms at the beginning of the heat cycle usually starts with her paying a great deal of sttention to and licking at her vulva frequently, and there is some hard swelling around the vaginal area. She will begin dark red bleeding from the vagina. The flow may be fairly heavy the first few days and usually decreases in amount over the next week. The color also changes from dark red to salmon color as the heat progresses. The vulva, or area around the vagina, swells considerably and then begins to soften, as her progesterone level rises and her body prepares to release the eggs from the ovaries. She will curve her tail over to the right or left side as she becomes closer to the actual mating time and will urinate frequently to spread her scent for the males.


You can avoid blood spots in the house by putting little boy's jockey type underware with a fly on her. Place a Light Days pad into the shorts and then put the pants on backwards, so that the tail comes out the fly. Change the pad regularly as needed through the day, and let her relieve herself.

Disponsable kiddies 'pull-ups' can also be used, by quite expensive.

There are "Doggie "heat" diaphers out there in Pet Stores and Vets office.

If you are planning to Breed her, and dont want to risk a "miss", there are tests the Vet can do to pinpoint the day of ovulation or you can do it yourself by using a "Premate Test".

Some females are very determined to ot be bred, and will attack the male viciously. Other females will breed with every dog in the neighborhood if they are given the opportunity to do so.

Always remember though that a pregnancy and delivery can pose a great risk to your dog. Some dogs die as a result of a pregnancy and certainly puppies die.

 If you do not want to have puppies at this time, you must exercise great care and caution through this 3 week period. Do NOT take her for walks at all, but keep her confined to a fenched back yard for the whole time. The reason for this is that she will urinate frequently while on a walk, just to let the boys knowshe is available. The males will pick up the scent and follow her trail to your home. You really don't wanta motley collection of canine suitors hanging around your house.


If you don't ever want to have puppies, then take her to the vet to have her "Spayed"(not Spaded, as some people call it). This common operation removes her uterus and her ovaries.Surgical removal of the ovaries(spaying) therefore prevents the egg production as well as the cancer causing estrogen.Spaying is an operation requiring as anaesthetic and stitches to close them abdominal imcision. The dog needs recovery time, but she recovers her activity level much faster than a human and do not seem to have the same pain level that humans have.Have your female dog spayed before she has her first heat unless she is a wonderful specimen of the breed and should reproduce or you want to "Show" her at a dog show. Spaying does NOT change her temperament, and will not make her fat. Diet and exercise control are in your hands as are unwated or unplanned puppies.

The Pregnant Dog

Female dogs pregnancy time line cycles

The Pregnant Dog

Pregnancy in a female dog- properly called a bitch, last nine weeks. We determine the birthing date from the date of the first mating. Some bitches will whelp(deliver their puppies)anywhere from day 59 to day 63. As the owner, you will make no changes to her diet for the first 5 weeks. Often, in the 3rd week after mating, she will go off her food for about 10 days. I compare this to the human'morning sickness' although a dog does not usually vomit.

You will notice that her vulva- the area around her vagina, did not return to normal small size it was before mating, but looks rather enlarged. There is normally no discharged durning a pregnancy. If you do see discharge, then take her to go see the Vet. She may have an infection, or be losing the litter, or have developed a case of Pyomtra, which, if left untreated, can kill her.

She needs a good exercise program, which involves a daily run to make sure all her muscles, including her uterine muscles, are in top condition. She also needs a very high quality diet. This is not the time to scrimp on her feeding formula. Mother Nature tries to insure the survival of the species, so if the diet is lacking in any ingredient, clcium or zice for example, the developing puppies (whelps) will take fromthe mother's body what they need to grow healthy, and therefore her body will become depleted.


At week 5, her nipples will become deep pink in color, and you may notice that she is thicker around the waist and broader around the rib cage. Now you should increase her feeding by 25%. Give her a daily Vitamin supplement from your Vet.

At week 6, increase her feeding again by 25% and divide her feedings into 2 meals a day. You will notice that she is sleeping a little more now.

At week 7, increase her meal amount again by 25%. Begin making preparations for the arrival of the puppies. Build a Whelping box for her and put it in a quiet room where she will be undisturbed by other pets and people and in an area that is easy to keep warm. Decide how yoou will heat the area where the new puppies will be. It needs to be about 85 degrees until they are 3 weeks old.

At week 8, increase the feed again by 25%. She is now eating double her normal amount. Begin feeding her 3 times a day now and make the exercise time shorter, but more frequent. Walking will be very tiring for her and she is very uncomfortable through the last week of the pregnancy. Begin taking her temperature rectally twice a day. The normal dog temperature is about 100.3F - 101.3F. It will normally drop to about 98. degrees F eight to twenty four hours before the onset of labour and she will refused to eat or drink anything.


Although animal whelping is a "natural event" this does not mean that the animal does not get into serious trouble if left unattended. Mother and puppies frequently die because the owner thoughtlessly left her alone during this crucial time.