Physical Development

Most pediatricians schedule a four-month well-baby checkup for around now. The doctor will check your child's size and weight, heart rate, breathing, abdomen (for hernias), skin, and genitalia. She'll assess strength and motor-skill development through a series of simple tests, and administer booster vaccines for DTP, HIB, and polio. Finally, she'll talk with you about sleeping habits, weaning, and introducing solids, which will happen sometime in the next month.

Social Development

Moms and babies who breastfeed value the opportunity for intimate, one-on-one time as much as the nutritional advantages it offers. However, many moms find that they need to wean their babies to a combination of nursing and bottlefeeding, or full-time bottlefeeding, in order to return to work or, as one mom put it, "to get my body back". When you decide it's time to wean, leave plenty of time for both of you to adjust to the change (experts suggest at least two to four weeks). Start by replacing one nursing session a day with a bottle, preferably given by a caretaker or other family member. (Babies are no fools--when they smell your milk, they may refuse to accept any alternative.) Continue offering skin-to-skin contact during feeding, and lots of gentle stroking to provide an extra measure of reassurance during the transitional period. And don't give up--eventually, she'll come around.

Intellectual Development

As recently as a few weeks ago, your baby reacted identically to a picture of a face and the real thing. Since then, she has learned to discriminate between herself and the rest of the world, and between pictures and real objects. She'll smile and vocalize more to a real face than to an image--even a mirror image, although her enjoyment of these is increasing--and more to some faces (yours, for instance) than others. She'll also distinguish between patterns and images of faces, responding with much more enthusiasm to the latter.

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.