You can tell a newborn puppy’s gender by looking at the belly between the hind legs. In male puppies, you’ll see a small raised opening roughly halfway up the belly, well below the umbilical cord. In female puppies, the only opening sits very close to the anus, with a smooth belly above it. The difference is subtle in the first few days of life, but once you know what to look for, it’s straightforward.
What to Look For on Male Puppies
Gently turn the puppy onto its back and look at the area between the belly button (or umbilical cord stump, in the first few days) and the hind legs. A male puppy has a small, round opening on the lower belly. This is the prepuce, which covers the penis. It looks like a tiny raised bump or button sitting roughly in the center of the abdomen, noticeably separated from the anus by a stretch of fur-covered skin.
You will not see testicles at birth. The testicles develop inside the abdomen and typically descend into the scrotum by about two months of age, sometimes a little later but rarely after six months. So at the newborn stage, don’t look for a visible scrotum. Focus entirely on the position of that small belly opening.
What to Look For on Female Puppies
A female puppy’s belly looks relatively smooth from the umbilical area down to the hind legs, with no raised bump in the middle. Her genital opening, the vulva, is a small leaf-shaped slit located very close to the anus, almost directly beneath it. The key difference is distance: in females, the genital opening and the anus are close neighbors, while in males, there’s a clear gap of belly skin between the penile opening and the anus.
The Distance Test
The single most reliable indicator is the distance between the anus and the genital opening. In males, this gap is roughly twice as long as it is in females. Research on anogenital distance in newborn mammals consistently shows this approximate 2:1 ratio between sexes. You don’t need to measure anything with a ruler. Just compare puppies in the same litter side by side, belly up, and the difference becomes obvious. The ones with a longer stretch of skin between the anus and the genital opening are males. The ones where the two openings are close together are females.
Why Nipple Counting Doesn’t Work
One of the most common mistakes is trying to use nipples to determine gender. Both male and female dogs have nipples. According to the American Kennel Club, dogs typically have between 8 and 10 nipples, and the number varies from dog to dog regardless of sex. Male and female nipples look similar, so counting or inspecting them tells you nothing about whether you’re holding a boy or a girl.
When and How to Check Safely
Ideally, wait until the puppies are at least 3 to 4 weeks old before handling them for a gender check. At that age, the anatomy is a bit more developed and easier to read, and the puppies are sturdier. If you need to check earlier, keep a few things in mind.
Newborn puppies cannot regulate their own body temperature. Being away from their mother and littermates for even a few minutes can cause them to chill quickly. Warm your hands before picking up a puppy, hold it gently cradled in your palms with the belly facing up, take a quick look, and return it to the mother promptly. Keep the entire process under a minute or two.
Watch the mother’s behavior. Some dogs are protective of their newborns and may become anxious or aggressive when you handle the litter. If the mother seems stressed, give her more time to settle before trying again. A calm mother makes the process safer for everyone.
Common Mistakes That Lead to Misidentification
In very young puppies, the genital area can be slightly swollen from maternal hormones, which sometimes makes female puppies look like males to an inexperienced eye. This swelling resolves within the first week or two. If you’re unsure, wait a few days and check again.
Another common error is confusing the umbilical cord stump with a penile opening. In the first couple of days after birth, the dried cord stump sits on the belly and can look like a small bump. The umbilical stump is higher up on the abdomen, closer to the ribcage, while the male genital opening is lower, between the hind legs. If you’re checking a puppy that still has its cord attached, note the position carefully before making a call.
Coat color and thickness can also make things harder. In dark-furred or heavily coated breeds, the genital area may be partially hidden. Gently parting the fur with your fingertip gives you a clearer view without needing to press or probe.
Confirming Later On
By 6 to 8 weeks of age, the anatomy is much more distinct. The male prepuce is clearly visible on the belly, and in most puppies, the testicles will have begun descending into the scrotum (or will be close to doing so). The female vulva remains a small, clearly defined opening just below the anus. If you identified the puppies at birth and want to double-check your work, this is the age when any earlier mistakes become obvious. A veterinarian can also confirm sex during the first wellness visit, which typically happens around this same time frame.