What gross motor skill should an infant be able to perform by 4 months?

By 4 months of age, an infant typically demonstrates the ability to roll from back to side. This milestone reflects the increasing strength and coordination of the infant’s muscles, particularly those in the neck and shoulders, allowing for more effective movements. The ability to roll is an important gross motor skill as it marks the transition towards more complex movements and indicates the infant’s increasing mobility and exploration of their environment.

At this age, infants are gradually developing muscle control and balance, which are necessary for rolling. Engaging in tummy time and other activities can support the development of these skills.

The other options presented relate to skills that require further development or are typically achieved at older ages. For instance, rolling from front to back usually occurs around 5 to 6 months, sitting unsupported develops around 6 to 8 months, and holding a bottle typically happens when infants are closer to 6 to 8 months as well. Each of these milestones occurs as the infant's muscle strength, coordination, and balance continue to improve with age.