By the age of four or five months, the infection-fighting antibodies with which babies are born have diminished. Thus, a number of babies get their first colds during these months, particularly if they have older siblings or are exposed to other children in day care. Although it is widely believed that breast feeding protects babies against colds and other infections, this claim has not been fully proven. To minimize the risk of infection, keep the baby away from people who have colds and other illnesses and, equally important, wash your hands frequently. Attempting to keep the baby’s hands and toys clean may be a losing battle, but is worth the effort, particularly when someone in the household has a cold or the flu.

The Growth Curve
In the three- to six-month period, infants continue to grow rapidly. The body’s fat stores increase, giving babies their characteristic and perfectly normal pudgy appearance. One of the fastest-growing organs during this period is the brain, which continues its development until the fourth year of life. The soft spot at the back of the skull (the posterior fontanel) closes by four months of age, while the soft spot at the front (the anterior fontanel) enlarges during the first few months of life, and closes when your baby is between nine and 18 months on average.

By about four months of age, many babies have doubled their birth weights. If your baby gains weight more slowly, there is no cause for concern provided the baby appears healthy and does gain some weight.

At three months, babies weigh around 12.5 pounds on average, and their length ranges from 22 to 25 inches. Between the ages of four and six months, they gain approximately one and one-half pounds a month and grow about an inch every month. Boys tend to be longer and heavier than girls. For a clear picture of how your baby grows during these months, see the growth charts in Volume II, A to ZEncyclopedia of Child Health & Illness.

Visiting The Doctor
During the three- to six-month period, the pediatrician should see your baby twice once at four months and once at six months. (Depending on your own pediatrician’s policies, these intervals may vary). During these well-baby visits, your child will be weighed and measured and his or her general development and health, including hearing and vision, will be assessed. To evaluate the hearing, the doctor will ring a bell or make a loud noise behind the baby’s back and observe the response. The pediatrician can screen the baby’s vision by shining a bright light in the eyes and observing how the baby blinks and follows the light source.

Immunizations administered during this period are the oral polio vaccine, the diphtheria-tetanus-pertussis (DTP) vaccine, and the Hemophilus influenzae type B (HiB) vaccine at four months; and the DTP (as well as, in some cases, an additional dose of HiB vaccine) at six months.

Milestones For The Three- To Six-Month Period
As mentioned elsewhere in this book, each child develops at her own, unique pace. On average, three- to six-month-olds acquire the following skills in approximately the order given below. Most babies will do some of these things sooner than expected and some a bit later. Remember that variation is the rule.

Overall, though, the three- to six-month period is a time of tremendous development during which new abilities and awareness emerge almost every day. A number of thrilling “firsts” take place during this time the first laugh, the first gurgle, the first utterances that sound almost like words. Once a new ability appears, you may see the baby practice it over and over again. On the other hand, some babies seem to back off and send new skills underground for a while soon after they develop. Either pattern is normal.

Some three-to six-month-olds do not like bathing in a tub. For these babies, a modified washup can often take the place of a full bath. With a washcloth, you can clean the baby’s hands, neck, underarms, trunk, arms, and diaper area.

?  Keep one hand on the baby whenever you are changing diapers on a changing table. Never leave a baby unattended on a changing table or bed, since babies can easily roll off.

?  Make sure the crib sides are always locked.

?  Use safety straps when you put the baby into an infant seat, swing, or stroller.

?  Remove mobiles and similar toys from the crib as soon as the baby is able to push up on the forearms. An active baby can easily become entangled in a mobile or start mouthing dangerous, small parts.

?  Never suspend a pacifier or toy around the baby’s neck with a string or ribbon. The string may get caught on part of the crib, stroller, or playpen and strangle the baby.

Sleeping Through The Night

Regardless of their sleep patterns, all babies go through several sleep cycles, waking at least one or two times each night. As they get older and feel hungry less often, however, they may go back to sleep after only a few minutes of whimpering or without any crying at all, particularly if they have learned to calm themselves by sucking a fist or gazing at a hand. Parents of calm, quiet babies often say their infants sleep through the night almost from birth, but this is never the case. Rather, these babies are lucky enough to know how to get themselves back to sleep when they wake at the end of a sleep cycle. Some babies need your help to get back to sleep. The following are helpful techniques:

?  When you want the baby to fall asleep, place her in a quiet spot where there is no activity to see. » Noise and light can easily wake babies this age. Therefore, you’ll all sleep better if the baby doesn’t stay in your room, where the sounds of squeaky bed springs, talking, and snoring can interrupt her slumber. » Give the baby a good feeding before putting her down for the night. If the baby wakes up hungry in the wee hours of the morning, try giving the last feeding as late in the evening as possible.

?  Don’t postpone the last feeding so long that the baby gets overtired. If the baby is worn out before going to bed, she is less likely to sleep well.

?  Avoid noise, excitement, and excessive activity in the hour or so before bedtime. If you hear the baby whimpering in the middle of the night, wait a few minutes before rushing to her aid.

?  If you need to feed or change the baby in the middle of the night, keep the room darkened and be quick and businesslike. Don’t pause to cuddle or play with your baby night is for sleeping.

To avoid this unpleasantness, look for signals that your baby may be getting frazzled and try to adjust your approach accordingly. Watch for yawning, fidgeting, flushing or mottling of the skin, and reluctance to look you in the eye and smile. If the baby shows any of these signs, tone down the environment, cutting out excess noise and activity. Some babies, of course, are more adaptable than others and actually seem to thrive on end-of-day excitement. If yours is one of these, enjoy. If not, try to adjust your evening activities to accommodate the baby’s needs.

Whether you include the baby in the family meal by giving her a bottle or nursing while you sit down at the table is a matter of personal preference. If you prefer a quiet, uninterrupted dinner, it’s probably better to put off eating until the baby is sleeping (but that may not happen until fairly late). Either way, a soothing bedtime routine just before or after the baby’s last nighttime feeding will be helpful. You may want to include a bath, depending on whether the baby responds to water by relaxing or getting wound up. A diaper and clothing change should also be part of the routine, as should a period of rocking, listening to soft music, or other quiet activity. Do not, however, get into the habit of nursing or rocking the baby to sleep at night.

During this period of the day, it’s best to keep things simple. Start dinner at a leisurely pace while the baby watches from an infant seat or mechanical swing. Alternatively, play soft music while you carry the baby gently from room to room, pointing out interesting objects. If the baby seems reasonably calm, bring out a few toys and enjoy a play session on the floor. Watch for signs of fatigue yawning, glazing of the eyes, and fretfulness. Whenever possible, try to have the baby nap at about the same time each afternoon, not so early that she will conk out for good at 5 P.M. (and be up and ready to play at 4 A.M.), but not so late that waking will occur later than your normal dinner hour. A late-afternoon bottle or nursing session can help the baby wind down. Avoid nursing the baby to sleep or letting her suck the bottle until dozing off. Not only does this keep the baby from learning to go to sleep unaided, it can also lead to tooth decay, especially once the first teeth have erupted, which often happens around the sixth month.