Introduction
The gestation period for dogs is typically around 63 days or 9 weeks, during which the most remarkable transformation occurs as the fertilized egg develops into a puppy. While pregnancy may seem short compared to the 9 months of human gestation, the changes throughout the canine gestation timeline are rapid and dramatic.
Within 24 hours of fertilization, cell division begins quickly and the small group of cells descends into the uterine horn. By 14 days the embryos have implanted into the lining of the uterus. Over the next several weeks the tiny puppies will develop limbs, organs, skeletons and eventually fur and distinct features.
At just 5 weeks gestation, the embryos are still extremely small but progressing through critical stages of early development. Monitoring fetal size and health is important during this time to ensure the pregnancy is proceeding normally.
Gestation Period in Dogs
The gestation period in dogs is approximately 63 days from conception to birth [1]. This period can vary slightly, from 56 to 70 days depending on the breed and other factors. The gestation is divided into several distinct stages of development:
Stage 1 (Days 1-7): Fertilization occurs, and the embryos travel to embed in the lining of the uterus. Cell division begins quickly.
Stage 2 (Days 8-14): The embryos implant in the uterine lining and the cells continue to divide. Early placental development begins.
Stage 3 (Days 15-21): The embryos develop into fetuses with recognizable features. Organogenesis occurs as the vital organs develop. The fetuses are about 1 inch long.
Stage 4 (Days 22-28): The fetuses have skeletal structures, claws, whiskers and hair. Their heartbeats can be detected. They are about 2 inches long.
Stage 5 (Days 29-35): The fetuses grow rapidly and their bones harden. Their faces have a dog-like appearance. They are about 3 inches long.
Stage 6 (Days 36-42): Hair covers the fetuses’ bodies and they begin to move in the womb. Their eyelids separate and eyes open. They are about 6 inches long.
Stage 7 (Days 43-49): The fetuses gain considerable weight. They develop coordination for simple movements. Their claws are fully grown and eyelashes develop. They are about 8 inches long.
Stage 8 (Days 50-56): The skeletons are fully developed. The fetuses move into whelping position in the womb. Their coats are complete. They are about 9 inches long.
Stage 9 (Days 57-63): The fetuses prepare for birth, orienting themselves and engaging into the birth canal. Milk glands enlarge in preparation for lactation. The average litter size is 5-6 puppies.
Fetal Development at 5 Weeks
At 5 weeks of gestation, the dog fetus is going through major developmental changes. According to Elanco (https://mypetandi.elanco.com/au/puppy-kitten/puppy-s-journeyfrom-single-cell-12-week-old-puppy), the fetus starts to look more like a puppy at this stage, with visible toes and distinct facial features forming.
The puppy’s organs are developing rapidly during this time. The heart is pumping blood, the stomach and intestines are starting to function, and the neural tube is closing to form the brain and spinal cord (Elanco). The eyes, mouth, and external ear flaps become noticeable.
In terms of size, sources estimate the fetus is roughly 1 inch (2.5 cm) long from head to rump at 5 weeks gestation, and weighs approximately 1/2 ounce (14 grams). The puppy’s limbs, nose, and eyelids are still developing and appear stubby. The umbilical cord connects the embryo to the placenta to receive nourishment from the mother (My Pet and I).
While still extremely small, the fetus takes on a more defined puppy shape by 5 weeks as major organ development continues. Distinct facial features like eyes and nose become visible, setting the stage for further growth and maturation.
Measuring Fetal Size
Fetal size is typically measured by crown-rump length (CRL) or the length from the top of the head to the rump. Using ultrasound imaging, vets can accurately measure CRL to track development. At around 5 weeks of gestation, the average CRL is 15-25mm, or about the size of a large grape. According to one source, “At this point, the dog foetus has nearly tripled in size and has already grown to 15 mm, or as big as a hazelnut.” 1
Ultrasound Imaging
Ultrasound is a crucial tool for monitoring fetal development and health during canine pregnancy. Vets will often perform ultrasounds throughout pregnancy to track the growth and position of the fetuses. According to the Animal Ultrasound Association, ultrasound allows vets to count the number of puppies, determine their heart rates, measure the skull and abdomen size, assess the placental function, and more 1.
At 5 weeks gestation, ultrasound can provide important information about the litter. The embryos will be visible on ultrasound at this point, though they are still very small. Typically they will measure around 1 cm or less at 5 weeks. The fetal skull and abdomen can be measured to assess growth and development. Heartbeats should be detectable as well. While the fetuses are still too small to get an exact puppy count, the vet will be able to confirm the pregnancy and gestational age based on the ultrasound 2.
Ultrasound allows close monitoring of pregnancy health and progress at this critical developmental stage. Tracking growth from week to week provides key insights into the fetuses’ wellbeing and gives owners and vets essential information to ensure the health of mom and pups leading up to whelping.
Factors Influencing Size
The size of a dog fetus at 5 weeks gestation can vary significantly depending on several factors. According to research, the most influential factors are:
Breed – Fetal size differs between breeds. Larger breeds like German Shepherds tend to have larger fetuses compared to smaller breeds like Chihuahuas [1]. This is likely due to differences in adult size between breeds.
Litter size – In larger litters, each individual fetus tends to be smaller in size. With fewer fetuses, there are more resources available for each one to grow [2].
Genetics – Just like in humans, genetics play a key role in determining fetal size. Studies show that fetal measurements in dogs have high heritability [1].
Maternal size – Larger female dogs generally have larger fetuses compared to smaller females. The mother’s size affects the room available for fetal growth [3].
Health & nutrition – Proper nutrition and health of the mother are essential for optimal fetal development. Deficiencies and illness can restrict growth.
Care of the Pregnant Dog
Proper care of a pregnant dog is crucial to help ensure the health of the puppies and mother. Some key areas to focus on are nutrition, exercise, and veterinary care.
Nutrition is especially important during pregnancy. Around the 5th week, it is recommended to switch to a high-quality puppy food and increase the amount by 25%. This provides extra calories and nutrients needed for the developing puppies [1]. After the 8th week, increase the amount by another 10-25%. Pregnant dogs should be fed small, frequent meals throughout the day.
Exercise is also a key component of care. Take the dog for short, regular walks and allow light playtime. This provides physical activity without overstimulation. As the pregnancy advances, walks should become shorter and easier [2].
Regular veterinary care helps monitor the health and progress of the pregnancy. Ultrasounds and checkups allow assessment of the puppies and mother. Tests can also screen for potential issues like parasites, infections, or nutritional deficiencies [3].
Common Health Issues
There are some potential health complications that can arise during the pregnancy in dogs. Some common issues include:
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Miscarriages – Miscarriages can occur if the fetus dies in utero. This may be caused by infections, trauma, hormonal imbalances, or genetic defects. Signs include vaginal bleeding, loss of pregnancy symptoms, and delivery of dead fetuses. According to VCA Hospitals, the risk of miscarriage is highest in the first 20 days of pregnancy [1].
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Pre-eclampsia – Also known as eclampsia, this condition involves dangerously high blood pressure. According to VCA, it usually occurs in the last 3 weeks of pregnancy and can be life-threatening. Symptoms include protein in the urine, vomiting, and seizures. It requires emergency treatment [1].
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Dystocia – This refers to an abnormal or difficult labor, where the puppy gets stuck in the birth canal. It may be caused by the puppy’s size or position. Signs include strong contractions without delivery of a puppy. This requires veterinary assistance, as it can be fatal for the puppies and mother [2].
Some other issues that may arise include gestational diabetes, mastitis, uterine inertia, uterine rupture, and hypocalcemia. Proper prenatal and veterinary care can help monitor for and treat complications if they arise [1].
[1] https://vcahospitals.com/know-your-pet/pregnancy-concerns-in-pets
[2] https://animalemergencycare.net/what-to-expect-when-your-expecting-pet-has-pregnancy-complications/
Preparing for Whelping
As your dog’s due date approaches, it is important to start preparing for the birth of the puppies. Most dogs give birth naturally, but there are some things you can do to help the process go smoothly.
Set up a whelping box in a quiet area of your home a week or two before the due date. This gives the mother dog time to get comfortable with the space. The whelping box should be draft-free, warm, and lined with comfortable bedding that you can change out as needed. Newspaper or puppy training pads under the bedding will help absorb fluids during the birthing process.
Have clean towels, dental floss or string, and scissors on hand to tie and cut the umbilical cords after each puppy is born. You may need bulb syringes or suction devices to clear fluid from the puppies’ mouths and noses right after birth. Your veterinarian may prescribe oxytocin spray to have on hand to help stimulate uterine contractions if your dog is struggling.
Make sure your dog is eating high-quality puppy food for extra nutrition in these final weeks. Take your dog’s temperature twice a day as her due date approaches – a temperature drop below 100°F signals that labor will likely start within 24 hours.
Let your veterinarian know the due date and have an emergency contact number on hand in case complications arise during whelping. With some preparation and care, you can help your dog have a safe, successful birthing experience.
Conclusion
A dog’s pregnancy begins when fertilization of an egg occurs after mating. At 5 weeks gestation, the embryos are still in the early stages of development. While too small to be seen on an xray or felt by touch, ultrasounds can detect the fetal poles and heartbeats. At this stage, the average crown-rump length is around 0.6 cm. Size can vary based on the breed and number of puppies. Proper care and nutrition of the pregnant dog is crucial to support healthy fetal development. Milestones like visible puppy movement, and preparation for delivery will come later in the pregnancy. For now, concentrate on providing excellent antenatal care through diet, exercise, supplements, and veterinary checkups. With a focus on health in these early weeks, you can give the puppies the best start in life.