Less common is aggression directed toward newborns. This type of aggression is more common in dogs, although some cats will react aggressively in response to the sound of a baby crying. These cats may direct their aggression toward the infant or the adult holding the infant, but often the cats display redirected aggression—they attack the nearest target, either a person or another household pet. Dog or cat aggression toward infants that is caused by fear can often be overcome through separation and desensitization and counterconditioning. This behavior modification involves engaging the pet in an enjoyable activity while briefly exposing it to the infant at a safe distance. Enjoyable activities include tossing treats that are kept at the changing table whenever a diaper is changed or giving a dog a prestuffed hollow toy or sterilized marrow bone before sitting down to feed the baby. Some new parents may be able to toss treats across the room to a dog while giving the baby a bottle or nursing.

In other cases, dogs show true predatory behavior toward infants. This behavior is less common in cats because movement is such a strong trigger for feline predatory behavior, and newborns just don't move that much. These dogs will not show any of the typical signs of fear or anxiety, such as flattened ears, tucked tails, yawning, or lip licking. Instead they tend to be aroused and focused on the baby. These dogs are showing the early stages of prey acquisition—focusing on the prey and beginning to stalk it. Some of these dogs are determined to get at the "prey item" that has entered their homes. This situation is dangerous, since a predator's goal is the kill. These dogs must be kept strictly separated from the infant. They may be able to be reintroduced to the child once the child is old enough to act like a person (e.g. sitting upright, walking). Until then, access to the child is not allowed. A similar approach can be used with cats showing this sort of hunting behavior toward a newborn.

Making introductions before baby comes

Some dogs may be anxious about things that roll or may try to bite at wheels (e.g. herding breeds), so parents who plan to take family walks should start walking such dogs with a stroller before the baby is born. This training may elicit some stares and comments from the neighbors, but it will be worth it when the parents, baby, and pet can enjoy fresh air and exercise because of a previously established positive experience.

If pets are extremely sensitive about sounds, expectant parents can work on desensitizing their pets to baby sounds by playing recordings of baby sounds. But not all animals respond to recorded sounds, so before embarking on a course of desensitization, the owners should test a pet's reaction by first playing the sounds at a real-life volume. If the pet shows any signs of arousal, fear, anxiety, or aggression, then desensitization should be undertaken. The owners should start by playing the sounds at a volume low enough that no reaction is shown. While the sounds are playing, owners should use positive reinforcement techniques, such as giving treats, feeding meals, playing with toys, or petting or brushing the pet. Over several sessions, the owners should very gradually increase the volume until the pet has no reaction to the sounds at normal volume.

Sit, Rover, sit

One of the most important things to teach dogs is not to jump up onto people—both people who are standing and people who are sitting on furniture. Ideally, all dogs should learn this, but it is even more important when there will soon be an infant in people's arms or on their laps. Preventing this behavior can be fairly easily accomplished by teaching and reinforcing, using reward-based methods, an alternative behavior such as sit. A reward-based method is much more effective with most dogs than punishment-based methods such as kneeing the dog in the chest or squeezing the dog's paws. In addition, a reward-based method does not carry the risk of evoking pain- or fear-based aggression.