First trimester: Weeks 1 to 3, days 0 to 21
Week 1Days 0–7
Fertilization and first cell divisions
- Inside
- Eggs are fertilized in the oviducts and the embryos begin to divide. Nothing is visible and she acts normally.
- At home
- Keep her on her usual adult food and routine. Do not add supplements, and ask your vet before any vaccine, flea treatment or dewormer.
- Vet
- No visit needed yet. If you are planning ahead, book the day-25 to day-30 ultrasound now.
Week 2Days 8–14
Embryos travel to the uterus
- Inside
- The embryos move into the uterine horns and space themselves out. They are still microscopic.
- At home
- Avoid any medication, including spot-on flea and tick products, unless your vet says it is safe in pregnancy.
- Vet
- Nothing routine this week.
Week 3Days 15–21
Implantation
- Inside
- Around day 16 to 18 the embryos attach to the uterine wall and the placentas begin to form.
- At home
- Some dogs become clingy or have a slightly reduced appetite for a day or two. Keep exercise gentle and regular.
- Vet
- Plan the confirmation scan for the end of this week or the next.
Second trimester: Weeks 4 to 6, days 22 to 42
Week 4Days 22–28
Confirmation window
- Inside
- Embryonic sacs are about the size of a walnut. Heartbeats can be seen on ultrasound from about day 25.
- At home
- Her nipples may enlarge and turn pink. Keep her diet unchanged unless your vet advises otherwise.
- Vet
- Abdominal ultrasound at about day 25 to 30 confirms pregnancy and heartbeats. It is not reliable for counting puppies.
Week 5Days 29–35
Organs form
- Inside
- The embryos become recognizable fetuses as eyes, claws, whiskers and palate form.
- At home
- Start moving her gradually to a high-quality puppy or growth diet, increasing portions in small steps over the next weeks.
- Vet
- Discuss diet and any health concerns at this point.
Week 6Days 36–42
Skeletons begin to harden
- Inside
- Fetal bones start to mineralize and her belly begins to enlarge.
- At home
- Split meals into three or four smaller portions as the growing uterus leaves less room for her stomach.
- Vet
- Nothing routine unless she is unwell.
Third trimester: Weeks 7 to 9, days 43 to 63
Week 7Days 43–49
Fully formed, rapid growth
- Inside
- Puppies have hair coats forming and grow quickly. Her belly is clearly larger and you may feel movement.
- At home
- Set up the whelping box in a quiet room at 75 to 80°F (24 to 27°C) so she can get used to it.
- Vet
- Book the X-ray for days 50 to 55.
Week 8Days 50–56
Count the puppies
- Inside
- Skeletons show on X-ray, so the puppies can be counted. Milk may begin to appear.
- At home
- Stock your whelping supplies. From day 56, take her rectal temperature twice a day.
- Vet
- X-ray at about day 50 to 55 gives a count and a view of head size against her pelvis.
Week 9Days 57–63+
Labor window
- Inside
- Puppies are mature. Labor can start any time from about day 58 if she was dated from ovulation.
- At home
- Watch for a temperature drop below 99.0°F (37.2°C), nesting, panting and refusing food. Active labor usually follows within 12 to 24 hours.
- Vet
- Know your emergency clinic. Call if she goes more than a few days past day 65 from ovulation without labor.