Method 1: Watching for Physical Changes
1, Watch for nipple color change. One of the earliest hints that a dog might be pregnant is if she “pinks up.” This refers to a change in her nipples which makes them appear a rosier color than normal, slightly swollen and more prominent. This sign can develop 2 - 3 weeks after conception.
2, Be aware of body changes. A pregnant dog’s body shape doesn't change until the second half of pregnancy. Between about 4 - 5 weeks her waist begins to thicken and her tummy fills out.
3, Do not increase food ration prematurely. A pregnant dog should be given increased food in the final third of pregnancy, but many owners tend to increase their dog's food ration too early. The additional calories lead to fat being laid down in the abdomen, which is often mistaken for a sign of pregnancy. It is not possible for the layman to discern whether her enlarged abdomen is due to fetuses taking up room, or fat.
4, Monitor continuing body changes. In the final third (weeks 6-9) of pregnancy, the dog’s belly becomes rounded and distended. Her mammary glands start to develop and become more obviously swollen, as they get ready to produce milk.
5, Look and feel for puppy movement. In the final third of gestation, you may be able to see the dog’s flanks moving as the puppies wriggle around in her womb. If you place your palm flat against her side where you see the rippling, you might be able to feel movement.
Don't be too disappointed if you can't feel anything. The puppies are deep within her tummy and each pup is floating is a sac of fluid, so it isn't always possible to feel the actual outline of a puppy.
Method 2: Noticing Behavioral Changes
1, Do not expect drastic changes. All dogs react individually to pregnancy. Some may be quieter and more tired early on, but a dog who is unwell may also be quiet, so this sign is an unreliable predictor of pregnancy.  The average female dog behaves largely the same as usual until the last third of the gestation.
In the final third of pregnancy, the dog’s size makes it more difficult for her to move around, and she may want to sleep more.
2, Expect appetite changes. Towards the end of pregnancy, the dog’s will womb grow larger and take up more space in her belly. She won't be able to accommodate large meals, so she'll start wanting to snack, eating a little at a time more frequently.
3, Watch for nesting. When it is nearly time for her to deliver the pups, the dog may start to nest.  She will gather blankets or clothing in a secluded place as she prepares a suitable safe warm environment for her imminent new arrivals.
The exact timing of nesting varies from 2-3 weeks to 2 - 3 days prior to giving birth.
Method 3: Getting a Professional Diagnosis
1, Visit a veterinarian. If you suspect that your dog is pregnant, it is worthwhile to visit the vet to confirm your suspicion. There are various methods a vet can use to definitively confirm pregnancy.
2, Get a physical examination. The vet will examine the dog and pay special attention to gently feeling her tummy.  By palpation (feeling from the outside of her belly) the vet can sometime feel the womb and the outline of a puppy inside. However, this is much more difficult than it sounds because it is easy to mistake a puppy for feces in the bowel, and vice versa.
The ideal time to feel a pregnancy is between day 28 - 35 after conception. Before this, there is not enough difference to feel to tell the vet she is pregnant. After this, the puppies can be mistaken for other things such as food in the gut.
3, Check for heartbeats. In late pregnancy (week 6 onwards), the vet can sometimes hear fetal heartbeats by holding a stethoscope to the dog’s belly. However, this is much more difficult than for human babies because of the rustling of the dog's fur coat and the fact that dogs have round, not flat, tummies.
4, Perform a blood test. The gold standard to test for pregnancy is for your vet to run a blood test that looks for the presence of a pregnancy hormone called Relaxin.
The hormone is only reliably present after day 28 of the pregnancy. If the test is run before this date it is possible to get falsely negative results, where you believe the bitch isn't pregnant when she is.
A positive result at any point, even before day 28, does confirm pregnancy.
5, Have an ultrasound. The method that can confirm pregnancy the earliest is an ultrasound. A skilled ultrasound operator can pick up puppies on the scanner from around day 16 onward.
In a docile bitch the scan can be done without sedation.
The operator will need to clip fur on the tummy of very furry dogs so that the probe can make good contact with her skin.
6, Ask about getting an x-ray. With the widespread use of ultrasound, the need for x-rays in pregnancy has decreased. The main reason to x-ray a pregnant bitch is in late pregnancy, to count how many puppies are present in the womb.
This information is useful so that the owner knows when all puppies have been safely born. It can alert an owner that the bitch's labor has stopped but she still has a puppy inside.
Method 4: Diagnosing Early Pregnancy Signs
1, Be patient. A dog may not show any signs of pregnancy in the first 2-3 weeks (which is the first third of the pregnancy). Her appetite should remain normal.
Pregnant female dogs absolutely do suffer from morning sickness like people do, however not until approximately day 21 after being mated. It usually lasts 1-2 weeks. Also on day 21, you can look at your female's gums. If the mating took, her gums will be white instead of the normal pink. This is because the fetus' are attaching in her uterus and the blood in her body is gathering there, so for a day or two, her gums will appear white. There is nothing to worry about. If it continues after 2 days, call your vet.
2, Notice any mood changes. Some people first suspect their bitch might be pregnant because she is a bit quieter than usual, but this is more anecdotal observation than proven fact. Pregnancy causes changing hormone levels and this affects each dog differently.
Some dogs may become quieter than usual, others may become more affectionate and clingy, and still others could withdraw and want to be left alone.
3, Watch for other signs of illness. Whilst a change in a dog’s apparent mood or behavior can indicate pregnancy, this is a vague sign that could also indicate that she is unwell. Therefore, you should monitor her closely for any symptoms of ill health such as loss of appetite, vomiting, diarrhea, coughing, sneezing, or vaginal discharge.
If your dog has been mated but subsequently goes off her food in the next few days or weeks, this is unlikely to be related to pregnancy and she should be checked by a veterinarian. This is also the case if you see a vaginal discharge (not normal during pregnancy) or if she is vomiting regularly.
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