Place your finger in your newborn's palm and she'll curl her fingers around it and hold on tight. Experts say this grasping is actually a reflex inherited from our tree-dwelling ancestors. Today, doctors check for it, as well as other reflexes, to assess a newborn's nervous system.
As babies gain control over their muscles, these reflexes gradually disappear. (If they don't, consult your pediatrician.) Meanwhile, observing them during the first few months can reassure you that all is well with your infant's neurological health.
A healthy baby will move his feet up and down, as if he's marching, when held under the arms in an upright position. (Be sure to support his wobbly neck muscles.) You can also provoke this response by brushing the top of his feet or letting them touch a flat surface, but doing so won't help him learn to walk any faster. In fact, the reflex usually disappears after two months.
"When a baby suddenly flings her arms out, then pulls her hands back to her chest with a jerk, that's the Moro, or startle, reflex," says Catherine Dundon, M.D., a pediatrician at Vanderbilt Children's Hospital, in Nashville. A newborn may display the Moro reflex in response to a sudden change in temperature, such as when you're changing her diaper, a loud noise, or a vigorous movement -- when you scoop her up unexpectedly, say. The Moro reflex may be accompanied by an arched back. This reflex too goes away after a couple of months.
A newborn will automatically suck on your finger if you put it in her mouth. This urge is so strong and develops so early that some babies are born with a blister on their lips from having sucked on their fingers while in the womb. The ability to suck ensures that new babies will get nourishment to survive from either a breast or a bottle. But as they become more conscious of the comfort it brings, they'll suck on a thumb, pacifier, or toy to calm themselves.
Hold a newborn at his mother's breast and he'll turn his head toward the object of his desire -- milk! You can also induce this reflex by stroking your baby's cheek, says Dr. Dundon. As though a breast is there, he'll turn toward the source of touch. So when feeding your infant, don't work against this reflex by trying to push the baby's far cheek toward the breast or bottle. Instead, stroke the cheek nearest the "target" breast to get his head to turn toward it. At around 4 months, the rooting reflex should disappear.
When a newborn turns her head to one side, her arm on that side straightens out, while the opposite arm bends up in an "en garde" position (sometimes called the "fencing posture"). If this particular reflex persists, it can indicate a neurological condition, such as cerebral palsy, so parents who observe their baby doing it beyond 5 to 7 months should alert their pediatrician.
The palmar grasp (when a baby clutches a parent's finger with his hand) and the plantar grasp (when stroking the sole of his foot causes him to fan out his toes, then grip with them) begin to diminish after just a few days. Both disappear completely before a baby's first birthday, but until then the palmar reflex can be a lovely way to court a big sister or brother, says Dr. Dundon. "Say to the older sibling, 'Look, your baby brother is holding your hand! He must love you!'"