Can puppies be missed in a pregnancy ultrasound?

The one question almost all pet owners ask during any ultrasound examination is ‘Are you sure doctor?’ Well, the honest answer is I am as sure as I can be. If you ask any veterinarian if he or she could have missed one or two puppies in the ultrasound, the answer is always yes. But before you get all mad that the poor vet doesn’t know how to do his job, let me explain it a bit further.

First of all, the main purpose of an ultrasound exam is to detect dog pregnancies and to see if the fetuses are alive.  And as with any other diagnostic tool, ultrasound has its limits. So if you end up with more puppies than you expected in your whelping box, it’s not your vet’s fault ☺️

First of all, you need to understand what’s happening during canine pregnancy. Secondly, you need to understand the capabilities and limitations of ultrasound scans and what to expect from this diagnostic tool. 

So, let’s get started, shall we? 😊

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While I am a veterinarian, this article is not intended to replace professional veterinary advice. If you have any medical concerns about your pet, consult your vet immediately. Always seek professional assistance if you are unsure of your pet’s health.

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Understanding pregnancy in dogs

Dogs are pregnant for 62-64 days, which can vary slightly depending on the breed and litter size. Smaller dog breeds tend to have shorter gestation periods, while larger breeds or dogs with larger litters may have slightly longer ones. However, it’s important to note that a dog can deliver healthy puppies even if they fall slightly outside this time frame. 

Basically, it’s the same as with humans – I gave birth a week after my due date, I guess my baby wasn’t ready when some statistic said she should be 😛 and it’s the same with female dogs. 

Small breeds tend to have small litters, while bigger breeds tend to have more puppies and somewhat easier birth. 

Symptoms of pregnancy in dogs

Dogs, like humans, go through various physiological changes during pregnancy. Here are some common signs and symptoms to look for:

• Changes in appetite: Some dogs may exhibit changes in their appetite. They may become more finicky or, conversely, ravenous
• Weight gain: Well, obviously, pregnant dogs gain weight as their pregnancy progresses 😃
• Nesting behavior: Many pregnant dogs will exhibit nesting behavior, where they create a comfortable spot to give birth
• Abdominal enlargement: As the pregnancy advances, you’ll notice a gradual enlargement of the abdomen
• Mammary gland changes: The mammary glands will become larger and firmer in preparation for nursing the puppies
• Behavioral changes: Some dogs may become more affectionate, while others might be more withdrawn
• Morning sickness: Some unfortunate pups may experience morning sickness
• Increased water consumption: Expecting dogs may drink more water than usual to support the developing puppies
• Vaginal discharge: In some pregnant dogs you may notice a clear, mucous-like discharge

Now, here’s a little canine embryology crash course:

Canine embryotic and fetal development: 

Dogs have two uterine horns. The fertilization occurs in oviducts, after several days the early embryos (zygota) descend to uterine horns where they implant. From then on the canine embryos develop in both uterine tubes. 

1. Phase: The period of the ovum

The first phase occurs right after fertilization. The fertilized eggs start to grow – their cells start to rapidly multiply and differentiate. These blastocysts descend in the uterine horns and begin the process of implementation (embedding in the uterine lining). 

Fun fact: apparently these blastocysts can migrate from one uterine horn to the other. I guess they are searching for the implementation sweet spot 🙂

This period is also marked by a rapid increase in progesterone levels. 

2. Phase: The period of the embryo

After the uterine implementation, the embryos continue to grow. To cover their nutritional needs, a placenta is formed around each embryo. The placenta supplies each baby with all the necessary nutrients, hormones, water, and oxygen. It also removes waste and carbon dioxide. It’s a direct connection between the pup and the mum. 

Cell differentiation initiates the development of organ systems, including the formation of the heart, liver, and nervous system. 

3. Phase: The period of the fetus

The fetal stage begins at day 35. This stage sees the further development and maturation of the heart, lungs, kidneys, and other vital organs. Bones also harden, and the features of the puppies, such as coat color and pattern, become more defined.

During the fetal phase, the puppies start to grow rapidly. 

Each fetus is surrounded by fluid-filled sacks formed by the placenta. The outer sack usually breaks in the birth canal, and the puppies are born enclosed in the inner sack. 

At the end of the fetal phase, your dam’s progesterone levels start to drop and right before the birth, there’s a rapid drop in her rectal temperature. 

Okay, now that you know the basics, let’s talk about pregnancy diagnosis 😊

Pregnancy determination in dogs

Canine pregnancy is a complex process that requires careful monitoring and management. Early diagnosis is therefore key for every dog breeder. You want to know if it all worked out, right? ☺️

On top of that, we need to determine if we are dealing with real pregnancy or false pregnancy (also called phantom pregnancy, pseudo-pregnancy, or pseudocyesis) or some other health issue. 

Important note: while we have guidelines on when something should occur, you need to remember that the date of mating doesn’t have to correspond with the date of conception. Sperms can survive for days in the uterine tract and the actual fertilization can occur even days later than mating.

So what are the main diagnostic tools to detect canine pregnancy in veterinary medicine? 

Abdominal palpation:

Remember the embryonal stage? Embryos and their protective sacks form small swellings in the uterine horns. These tiny swellings are palpable ~21 days after fertilization. Well, that is if your dam is feeling cooperative and is not overweight 😊

The best time for abdominal palpation is 28.-30. days after ovulation, but it can vary individually. 

In the fetal phase, distinguishing each fetus becomes harder as they are crumped together in a small space. 

Later in the pregnancy, you can feel fetal movement when you touch your pregnant dog’s belly. 

Relaxin test:

This is a blood test that detects the hormone relaxin. It is produced primarily by the placenta after 30 days of pregnancy.

A positive result in the relaxin rapid test always confirms a dog’s pregnancy since it’s only produced in pregnant bitches. 

Your vet might also check hormone levels during your dog’s pregnancy, but they are used to monitor the pregnancy and assess your pup’s health status. For example, progesterone levels stay high after ovulation regardless if the dog is pregnant or not and are therefore not the best way to confirm a pregnancy. 

Radiography:

The calcification of the fetal skeleton begins relatively early, but you need to wait for day 45.-48. to see them with routine radiography.

This means that doing the X-rays too soon can cause false negative results – you just won’t see the puppies, because their bones are yet not mineralized enough. 

The image gives us valuable information about the size of fetuses and, their positions, and helps us detect skeletal abnormalities and deformities.

Radiography is also the best method for estimating the size of the litter. Late radiography (day 55. and more) is the most accurate time to assess the number of fetuses. 

And while X-rays are great for accurately diagnosing pregnancy in dogs, they don’t tell us if all babies are alive and viable or not. 

Abdominal ultrasound:

Radiographic diagnosis of pregnancy used to be the standard method before the introduction of ultrasound technology.

Nowadays, ultrasound can diagnose even the early stages of pregnancy (before calcification) and it’s an invaluable tool for monitoring your dog’s pregnancy and fetal viability. In other words, we also know if the puppies are alive 😎

Overall, we use all or most of these diagnostic tools to confirm pregnancy, monitor fetal growth, assess the health of the developing puppies and their mum, and detect any possible defects or complications. 

Now back to ultrasound…

Understanding ultrasound technology

Ultrasound is a diagnostic tool that uses high-frequency sound waves to create images of the inside of the body. It is a non-invasive and painless procedure that is commonly used to diagnose a variety of conditions. 

An ultrasound machine consists of a transducer, which is a handheld device that emits ultrasonic waves, and a computer that processes the signals and creates images. The transducer is placed on the skin over your dam’s belly (and a lot of gel 🙂 ). The ultrasonic waves penetrate the body and bounce back to the transducer, creating an image on the computer screen.

Ultrasound technology has advanced significantly in recent years, and modern machines can produce high-quality images with great detail. 

There are various types of ultrasound machines available in the market, ranging from portable machines to high-end machines. Portable machines are affordable and can be carried around easily, making them ideal for practices that have limited space. 

High-end machines, on the other hand, offer advanced imaging capabilities but are expensive.

In general, there are several categories of ultrasound:

• B-mode ultrasound, also known as 2D ultrasound, is the most common type. It provides a real-time, two-dimensional ultrasound image of the tissues and structures, and helps evaluate the organs of newborn puppies, such as the heart, liver, and kidneys.
• Doppler ultrasound assesses cardiovascular health and blood flow. It can identify any heart murmurs, arrhythmias, or congenital heart defects.
• Color Doppler and Power Doppler ultrasounds delve deeper, pinpointing abnormal blood flow patterns and microcirculation. Color Doppler is excellent for identifying abnormal blood flow patterns, particularly in neonates with suspected heart or vascular issues.
• Advanced 3D and 4D ultrasounds take neonatal care to the next level, providing detailed, three-dimensional images and real-time, moving views of complex structures.

You can say that an ultrasound can help us detect congenital defects and monitor the well-being of growing puppies. This is the main difference between ultrasound and radiography. We can tell if all puppies are alive and monitor their health.

Why is ultrasound not accurate for counting the number of puppies?

The main difference between ultrasound and radiography is that ultrasound is dynamic – it’s a real-time moving picture. Yes, you can snap a photo, but the exam overall is not static. Everything’s moving inside.

In very early scans you can see gestational sacs (from as early as 20. days gestation). However, an early ultrasound scan can only confirm a pregnancy.  If you perform these dog pregnancy scans too early, you risk getting a false negative result. 

Later you can have a lookdividual puppy and its heartbeat. 

However, if there are many puppies, some of them may be positioned in a way that makes them difficult to see. This is especially true if the puppies are located in the back of the uterus or if they are small in size.

And sometimes the puppies move so much that some could be counted more than once. 

I know that knowing the exact number of puppies is important for a number of reasons. You may be wondering how to best prepare for the birth, or what to expect during the labor process. Or maybe as a new dog breeder, you want to start advertising your future litter of puppies. 

But nothing is 100% accurate, sorry 🤷‍♀️

However, your best option to get a somewhat accurate count is to take your pregnant pup for X-rays after 55 days gestation. And even then, this is what it looks like 👇

So how many puppies can you count? 😎(Hint: count only the skulls)

In conclusion, here’s the main difference between the use of ultrasound and the use of X-rays in canine pregnancy:

Ultrasound:

• great for early pregnancy detection
• great for assessing fetal viability
• great for detecting fetal defects and anomalies

X-rays:

• late pregnancy detection
• good for (relatively) accurate puppy count in the late weeks of pregnancy

Talk to your vet about your specific situation. You might need to repeat the exams or combine different methods to get the best results. 

A little warning at the end: beware of people offering very cheap scans or offering very early scans. 

Good luck! ☺️

❣️FREE BONUS FOR YOU! Printable whelping charts to help you keep organized during birth 🤗

References:

• Canine embryonic and fetal development: A review
• Pregnancy Determination in Dogs and Cats
• Management of Reproduction in Dogs
• Canine Pregnancy Part 1: Radiography Vs Ultrasound

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