Day 45 Canine Pregnancy: Final Fetal Growth and Whelping Preparation

A dog’s gestation period averages 63 days, placing Day 45 solidly within the third trimester (Weeks 7–9). This week marks the most substantial phase of the puppies’ development outside of organ formation. The litter now focuses on rapid weight gain, and their skeletal structures are hardening. This moment is critical for the expectant mother's management, demanding a drastic increase in nutrient intake and careful preparation for the upcoming whelping process. Owners must transition from routine care to heightened vigilance, ensuring the mother is supported for the physical demands ahead.

As a specialist, I confirm that successful outcomes rely heavily on the owner's responsiveness during this time, particularly regarding nutrition and clinical monitoring.

1. Fetal Milestones: Ossification and Maturation

By Day 45, the risk of structural birth defects from external interference has passed, but the vulnerability to nutritional deficits peaks as the puppies demand massive caloric and mineral resources from the mother.

Skeletal Ossification and Coat Development

Ossification Complete: The most significant development around Day 45 is the completion of skeletal ossification (hardening of the bones). The puppies’ skeletons—including the skull and spine—are now largely calcified, meaning they are hard enough to be clearly visible on an X-ray.
Final Features: The puppies are fully formed, with distinct claws, toes, and eyelids that are now closed. The fine hair (coat) and pigmentation are established, meaning their adult markings are fully set.
Growth Spurt: The puppies enter a period of exponential weight gain. The majority of the final birth weight will be added between Day 45 and Day 63. Their increasing size rapidly diminishes the space available within the mother's abdomen.

2. Intensified Maternal Physical Changes

Physical changes are now dramatically visible, impacting the mother’s mobility, appetite, and comfort. The strain on her body increases daily due to the sheer weight and volume of the developing litter.

Symptoms of Late-Stage Gestation (Day 45)

Abdominal Size and Puppy Movement

The abdomen is large, firm, and obviously distended. You should be able to place your hands gently on her abdomen when she is resting and feel the strong, definitive movements of the puppies, often described as wriggling or stretching.

Mammary Development and Leakage

Mammary glands are significantly enlarged and may feel firm. Some mothers begin producing colostrum (a thick, yellowish fluid) this week, or they may secrete a thin, milky discharge. This is a natural preparation for lactation.

Appetite and Digestive Compression

While energy needs are highest now, her appetite may paradoxically decrease. The sheer volume of the puppies compresses her stomach, making it difficult for her to consume large quantities of food. This requires changing her feeding schedule (see Section 4).

3. Day 45 Clinical Assessment: The X-ray Count

Around Day 45, the X-ray becomes the most accurate and valuable diagnostic tool for whelping planning, surpassing the accuracy of palpation and even late-stage ultrasound for counting purposes.

The Importance of Puppy Count

Since skeletal ossification is complete, a veterinary X-ray taken between Day 45 and Day 55 provides an accurate count of the number of puppies. This count is not merely for curiosity; it is a critical safety measure:

Delivery Monitoring: Knowing the exact number allows the owner to track the delivery process and ensure every puppy is successfully delivered, preventing retained fetuses that could be life-threatening.
Intervention Planning: For breeds prone to birthing difficulty (e.g., French Bulldogs, Boston Terriers) or if the litter is very large or very small, the count informs the veterinarian’s decision regarding potential elective Cesarean sections.

A final check of the mother's abdomen, placental location, and overall health status should be completed by the veterinarian during this visit.

Do Not Attempt Palpation: While a veterinarian can gently palpate the abdomen to feel the firm swellings of the uterus, owners should avoid deep or rough handling of the abdomen from this stage onward, as excessive pressure can risk injury to the mother or the puppies.

4. Maximizing Caloric Density and Hydration

The nutritional demands of the final trimester are immense. The mother's energy needs increase by up to 50 percent above maintenance levels by the time of whelping. Failure to meet these demands can lead to severe complications, notably **Eclampsia** (milk fever) postpartum.

Transitioning to a High-Calorie Diet

If not already initiated, the mother must immediately transition to a high-quality, high-calorie, nutrient-dense diet. The most common recommendation is to switch from standard adult maintenance food to a premium **Puppy Growth Formula**. Puppy food is specifically balanced with higher levels of protein, fat, calcium, and calories necessary to support fetal development and lactation.

Nutritional Goal	Action (Day 45 Onward)	Rationale
Calorie Increase	Increase daily food volume by 25 percent now, rising to 50 percent by Day 63.	Fetus gains 75 percent of its birth weight in the final 3 weeks.
Feeding Schedule	Break the daily food volume into 3-5 small, frequent meals.	Reduces discomfort from stomach compression and ensures steady nutrient flow.
Hydration	Ensure continuous access to fresh water.	Prevents dehydration, crucial for milk production and labor function.

5. Whelping Environment Introduction and Safety

The final three weeks are when the mother will begin "nesting"—an instinctual drive to prepare a safe, secluded location for birth. Owners must actively guide this process to ensure the location is clean, temperature-controlled, and accessible.

Whelping Box Introduction

Introduce the whelping box (a secure, comfortable enclosure) now, if you have not already. This allows the mother ample time to associate the box with security and privacy, reducing the chance she will choose an unsafe or inaccessible spot (like a closet or under a bed) for delivery.

The box should be located in a quiet, low-traffic area of the house.
Lining should consist of easily replaceable and washable materials, such as old towels, newspapers, or vet bedding.
The temperature should be maintained comfortably, as newborn puppies cannot regulate their own temperature effectively.

Exercise and Final Preparations

Continue moderate, gentle exercise, such as short, slow walks on a leash. Strenuous activity, jumping, or rough play must cease completely. The mother's energy should be conserved for the demanding process of labor. Finalize gathering all whelping supplies (towels, heating pad, thermometer, veterinary contact numbers) and organize the transport vehicle for potential emergency trips to the clinic.

Day 45 is a time for proactive management. By meticulously monitoring the mother's nutritional intake, ensuring her comfort, confirming the litter size through clinical imaging, and preparing the whelping environment, you significantly reduce the risks associated with delivery and establish the best possible prognosis for the mother and her future litter.