The first trimester is the most critical period in a little dog's life. During this time, little dogs go through rapid growth, so they need to be looked after with extra care. Here are some things to look out for in the first three months of a little dog.

1. Food care

During the first three months of dog’s growth, diet is crucial. Make sure to breastfeed until at least 6 weeks of age, and then wean. After weaning, a dog food designed for puppies should be provided to ensure they get enough protein and other elements.

2. Timed inoculation

Immunization is the key to healthy puppy development. During the first trimester, puppies should receive a series of vaccinations to protect against common canine diseases. Follow your veterinarian's recommendations and provide your puppy with timely vaccinations.

3. Avoid excessive play

While exercise is good for a puppy's health, excessive play can be harmful to developing bones and joints. Make sure the puppy gets plenty of rest and limit strenuous exercise, especially on hard surfaces.

4. Social training

The first trimester is a critical period for a puppy's social development. Expose puppies to other dogs and people for basic obedience training, and make sure they have a positive social experience. This helps to develop a friendly personality.

5. Periodic inspection

Take the puppy to the vet and make sure to get regular physical checkups. These tests can detect and address any potential health problems early.

6. Warm and comfortable environment

Make sure the puppy lives in a warm, dry, and comfortable environment. Their beds should be kept away from vents and damp places.

In general, the first three months of puppy care needs to be detailed, involving diet, health, social and other aspects. Provide a stable and loving environment for them to grow up healthy and happy.