Discovering the sex of your puppy is fairly straightforward when you know a few anatomical landmarks. Make sure to handle your puppy gently and carefully. If you can, try to wait until the puppy is 3-4 weeks old before trying to determine its sex. If you handle the puppy too much before it has had time to bond with its mother, the mother may reject the puppy.
Pick up the puppy gently.
Newborn and young puppies are very delicate. Handle them with care. Puppies can’t see or hear very well before they’re a few weeks old, so picking them up and holding them may make them nervous or fussy.
Never pick up a puppy by its tail! Slide your hand under as much of the body as possible to offer the best support as you pick up the puppy.
Handle puppies as little as possible during their first two weeks after birth. Over-handling them could upset the mother dog or harm the puppies.
If possible, wait until the puppies are at least 3-4 weeks old before trying to determine their sex. They will have had enough time to bond with their mother and develop a bit by then.
Hold the puppy in cupped hands.
Lay the puppy in your hands on its back, with its paws in the air. Make sure you support the puppy’s whole body with your hands so you don’t stress their spine. Don’t squeeze the puppy.
It may be easier if you have someone else hold the puppy so you can do the visual inspection.
You can also rest them on their backs on a warm towel spread on a table. This will help keep the puppy warm.
Newborn puppies cannot maintain their own body temperature for several weeks after they’re born. They can take a chill very easily. Don’t hold the puppy away from its mother longer than is necessary. 5-10 minutes should be the limit for handling young puppies.
Use a heating pad or hot water bottle wrapped in a towel in the puppy’s bed to help keep it warm.
Observe any distress.
If the puppy shows signs of distress, such as squalling or squirming, put the puppy back with its mother immediately. The mother may also become distressed if she isn’t used to you handling her pups. If you notice signs of her getting distressed, such as barking at you, put the puppy back with the mother.
Look at the puppy’s belly.
You will probably see a “belly button,” or umbilicus. This is usually located almost at the center of the belly, just below the rib cage. If the puppy was born within the last few days, the umbilical cord may still be attached. Once the umbilical cord shrivels and falls off — which should happen within a few days — there will be a little scar left behind on the belly. This scar is a slightly brighter color than the surrounding skin and feels a little bit thicker.
Look below the bellybutton or umbilicus scar.
If your puppy is male, there will be another small raised spot or “button” of flesh about an inch or so below the scar. This is the prepuce, or sheath, of the puppy’s penis. The prepuce will have a small hole at the center.
The prepuce may have little wispy hairs around it or even on it.
Do not attempt to pull out or unsheathe a male puppy’s penis until the puppy is at least 6 months old. Dogs have an os penis, or “penis bone.” You may damage the penis or penis bone if you attempt to forcibly unsheathe a young male dog’s penis.
Check for testicles.
Male puppies will have testicles, although you may not be able to feel them before they are 8 weeks old. If you can locate the testicles, they will be high up between the puppy’s hind legs.
Depending on your puppy’s size, its testicles will be about the size of a lima bean. By 8 weeks old, the testicles are usually enclosed in the sack-like scrotum.
Feel the puppy’s belly.
Unlike male puppies, female puppies will have smooth bellies (other than their umbilicus scar). Females do not have a prepuce.
Examine the puppy’s rear end.
A puppy’s anus is located directly under its tail. If your puppy is male, you will only be able to see its anus. If your puppy is female, you will see a raised, fleshy area just under the anus. This is the vulva.
The vulva of a female puppy is small and leaf-shaped. It has a vertical slit. It is usually located almost directly between the puppy’s hind legs. The vulva may have some wispy hairs on it.
Disregard the nipples.
Just like humans and other mammals, both male and female dogs have nipples. They will not inform you of a puppy’s sex.
Consult your veterinarian.
Puppies should have their first set of vaccinations at around six weeks old. If you can’t figure out what sex your puppy is, your veterinarian can help you with this during a routine visit.