Pregnancy in dogs

Gestation is the period from conception to birth. It averages 63 days from the day of ovulation (the normal range is 56 to 66 days). Note that the day of ovulation is not always the same as the day of breeding.

During the first few weeks of gestation there are few signs of pregnancy, except for a slight gain in weight. Occasionally a bitch may experience morning sickness. This usually happens during the third to fourth week of pregnancy, and is caused by the effects of progesterone, combined with the stretching and distention of the uterus. You may notice that your bitch appears apathetic, lacks appetite, and may vomit from time to time. Morning sickness lasts only a few days. Unless you are particularly attentive, you may not notice it at all. If vomiting occurs, feed several small meals spaced throughout the day.

By day 40, the nipples begin to darken and enlarge, and the belly is increasing in size. As birth approaches, the breasts enlarge and a milky fluid may be expressed from the nipples. (Note that many bitches have breast enlargement after a normal heat period, so this alone should not lead you to conclude she is pregnant.)

Abdominal ultrasonography can detect puppies throughout pregnancy, beginning as early as 18 or 19 days after ovulation, although many veterinarians prefer to wait until 21 days for increased reliability. The technique is safe and effective, and does not use radiation.

The dog’s uterus has two horns that meet in a central uterine cavity. Developing puppies, encircled by their placentas, lie within the uterine horns.

By palpating the abdomen, a veterinarian can tell by the 28th day after the last breeding whether a bitch is pregnant. The embryos can be felt as evenly spaced swellings about the size of walnuts in the average-size dog.

Abdominal palpation requires experience and a gentle hand. This should only be done by your veterinarian or an experienced breeder. There are other structures in the abdomen that may feel lumpy. Excessive poking and prodding can damage the delicate fetal-placental units and cause a miscarriage. If you would like to learn how to palpate for puppies, ask your veterinarian to demonstrate the procedure to you. After day 35, the fetuses are floating in capsules of fluid and can no longer be detected by palpation.

A blood test looking for relaxin levels can be done around 28 to 30 days of gestation. Relaxin is a hormone that increases during pregnancy. Another blood test in experimental development is for acute phase proteins. These are proteins that react to inflammation. In the case of canine pregnancies, the rise in these proteins is stimulated by the attachment of the embryos to the lining of the uterus (the endometrium).

Abdominal X-rays will show fetal bone structure at about day 45. X-rays are used as an alternative to ultrasonography, to distinguish among pregnancy, false pregnancy, and pyometra, and to estimate the size of the litter. X-rays should be avoided in early pregnancy, because the radiation could adversely affect the developing embryos before 45 days.

In late pregnancy, the abdomen becomes enlarged and pendulous. The movements of the puppies can be seen and felt during the last two weeks.