Dog gestation, week by week

Week 1: ovulation and fertilization

Days 0–6 after ovulation. The eggs are released still immature, which is normal in dogs. They finish maturing about two to three days later, and fertilization is completed around day 3 if sperm are already waiting. Through this week the embryos are in the oviduct, only a few cells across.

You will not see a reliable sign. She looks like a dog who was recently in heat. Appetite, nipples, and mood are not a pregnancy test. Keep her normal complete diet. Do not add calories, and do not add calcium. Skip new supplements, flea products, dewormers, pain medicines, and vaccines unless the clinic that knows her has approved them for pregnancy. Optional procedures can wait.

Week 2: embryos reach the uterus

Days 7–13. The embryos divide and travel. They enter the uterine horns around days 9–12 and can still cross from one horn to the other. An ultrasound cannot confirm or exclude pregnancy. A “negative” scan this week means the scan was too early.

There is still no outward change that separates pregnancy from a normal post-heat interval. Keep feeding a maintenance amount. Write down every mating date now, including the later ones, not only the first.

Week 3: attachment starts

Days 14–20. The embryos become blastocysts, enlarge, and stop migrating. A high-resolution ultrasound may show tiny fluid-filled vesicles around days 16–18. Many clinics would rather wait, because a scan this early is easy to misread. Attachment to the lining starts around days 20–21, at the end of this week or the start of the next.

The belly does not change in any useful way. Do not increase food yet. If she needs a medication, ask specifically whether it is acceptable in early pregnancy. A product that was fine last month is not automatically fine now.

Week 4: a heartbeat can appear

Days 21–27. This is implantation, and the first week a heartbeat can be seen. Attachment is underway around days 21–23. A heartbeat may show on ultrasound around days 22–25, depending on the machine, the dog, and how the abdomen was prepared. A practical confirmation visit is this week or early next — about days 25–30 — when a heartbeat should be easier to find. If a scan at the early edge is unclear, a recheck a few days later is more useful than deciding she is not pregnant.

A relaxin blood test can turn positive for some dogs late in this week, more reliably after about days 26–28. Relaxin supports a pregnancy diagnosis. It does not show that the puppies are alive the way a heartbeat does. Nipples may look pinker, especially in a first pregnancy. Plenty of pregnant dogs still look unchanged, and a false pregnancy can swell nipples later. Nipples are not proof.

Week 5: confirmation, not a puppy count

Days 28–34. Heartbeats are usually obvious on a standard ultrasound, and the zonary placenta can be seen. A veterinarian may feel uterine swellings, often around 1–3 cm near days 28–35. Palpation is easy to get wrong, it should not be a rough hunt at home, and it cannot count puppies.

A mild anemia of pregnancy begins around now and is expected later in the pregnancy. It is not a reason to start iron or calcium on your own. Keep calories at maintenance unless the vet has a different plan. Skeletons have not mineralized. An x-ray still cannot count pups.

Week 6: growth, and the first calorie increase

Days 35–41. Growth picks up. Fetal movement may be visible around day 35. Around days 38–40 the fetus becomes longer than the band of placenta around it, which some scanners use as a landmark. Energy needs start to rise.

If your vet agrees, begin a gradual increase and move toward a food labeled complete for growth and reproduction. Many clinics use a puppy food they already trust. Split meals so a full stomach is not competing with the uterus. Many feeding guides aim for roughly a quarter to a half more than her maintenance amount by the last week, not a sudden doubling. Do not add calcium. Extra calcium in pregnancy is a common home mistake and is widely considered to interfere with her own calcium regulation, which matters after whelping. Do not switch her to a homemade diet for pregnancy.

Ordinary leash walks are fine. Skip hot-weather exertion, rough play, and a new intense conditioning plan. One smaller meal because she feels full is common. Repeated vomiting, a full day of not eating, or lethargy is a call, not a watch-and-wait.

Week 7: the belly, and bone that is too early to count

Days 42–48. The abdomen is usually obviously larger by the end of the week. Mammary development increases. Skull and spine can start to mineralize around days 44–46, so an x-ray may show something and still undercount. If the goal is a puppy count, wait until day 55 or later.

Keep splitting meals. Gather the supplies on the whelping checklist so the last week is not a shopping trip. Clear or mucous discharge can appear as pregnancy advances and can be normal. Green or black-green fluid is not a “maybe” this week. That color is placental pigment. Call the clinic the same day if you see it this early.

Week 8: the box and the puppy-count x-ray

Days 49–55. Put the whelping box in the room where she will deliver and let her sleep in it. Limbs and pelvis become easier to see on radiographs toward the end of this week. Day 55 is a reasonable first day for a count. Many clinics schedule it over the next few days. The count is how you will know labor is finished. It can still miss a puppy, so treat it as the best picture, not a guarantee.

Milk may appear, or it may wait until the day of labor. Milk is not a due date. Neither is nesting a few days early.

Week 9: temperature, nesting, and the phone number

Days 56–62. Take a rectal temperature two or three times a day, at rest, with the same thermometer, and write it down. Learn her baseline before you look for a drop. Most resting dogs sit around 100.5–102.5°F (38–39.2°C). A drop of about 1°C (roughly 2°F) below her own baseline, sometimes under 99°F (37.2°C), often comes 8–24 hours before active labor. The temperature may rise again once labor starts. Not every dog gives a clear drop. A normal temperature does not mean she will not whelp tonight. An ear thermometer is the wrong tool for this decision.

Nesting, restlessness, and refusing a meal can start. Have the emergency number on the box. How to read labor itself is on the signs of labor page. If a cesarean is even a possibility, the clinic will want their own progesterone check near term. Home kits are easy to misread, and this page cannot time surgery.

Day 63: the expected day, if ovulation was timed

Most ovulation-timed dogs whelp on day 63, give or take a day. From the LH surge, that is day 65, give or take a day. If you only have a mating date, do not treat day 63 after the mating as the due date. Use the window from the due date calculator. If the window ends and labor has not started, call. Do not give oxytocin, calcium, or anything else to start labor unless a veterinarian tells you to for this dog.

The citations for the 63-day and 65-day clocks, and for the small effects of litter size and body weight, are listed on the pregnancy calculator page. Those effects are about a day or two. They are why the calculator shows a note instead of a new date.