Physical Development

As your baby passes the two-month mark, she's gaining coordination and learning to control her muscles; newborn reflexes like the Moro (startle) reflex are being replaced by voluntary actions. As a result, she may appear to move less, but this is only because her movements are smaller and more controlled. In the next month, she'll learn to exercise her arm muscles by batting at toys as well as performing the "baby push-up," pushing up with her elbows or hands when she's lying on her tummy. She may even start to roll over.

Social Development

At this age, most babies are tolerant and friendly to everyone--they haven't yet developed the distinctions between themselves, their families, and the rest of the world that cause separation anxiety in later months. They're especially enamored of older siblings, turning to look in the direction of their voices and smiling whenever they come in sight. Unfortunately, this love affair may be a one-way street. While older children (4 years and up) feel less threatened and are consequently able to enjoy their new sister or brother, toddlers tend to look at the new arrival as an intruder. It's important to remember that these feelings are normal, even when they're expressed in violent terms--such as suggesting you throw the baby out the window! But it's equally important to make a distinction between talking about feelings and acting on them.

Intellectual Development

Part of the tension between siblings may be caused by the fact that baby is still too young to play with older children. At this stage, your little one is starting to master independent play skills, such as rolling a ball. Later in the first year, she'll start to engage in parallel play--sitting side-by-side with another child but "doing her own thing", for instance, building separate structures from the same collection of blocks. After these skills are mastered, around the time she turns 2, she'll be ready to ready to interact socially with other children. Meanwhile, help her develop her play skills by getting down on the floor with her and letting her practice, interact, and explore.

Note: The information above offers general guidelines, but all babies develop differently, and few hit their milestones precisely when the conventional wisdom says they should. If your child was born prematurely, you may want to use your due date as a baseline for following baby's development.