There aren't too many medical problems that begin exclusively during this time period, but one of them, intussusception, can be especially dangerous. As you start solids and vary your child's diet, constipation often becomes a problem. Developmental delays become a little more apparent at this age, when it is more obvious that your child isn't meeting milestones, such as sitting up or rolling over.

And your baby will still be at risk for general childhood problems and infections, including eczema, reflux, diarrhea, and colds and coughs. If your child has reflux, it may continue to be just as bad at this age. For many infants, however, it begins to improve now as your baby is sitting up more and eating more solid foods.

In addition to watching for problems, don't forget your baby's four- and six-month well-child visits to your pediatrician to review your baby's growth and development and to get her vaccines.

Intussusception

Intussusception, which is a form of intestinal blockage that has some characteristic symptoms, can begin when an infant is three to four months old. Like babies with other forms of blockage, infants with intussusception have a lot of vomiting, which may be dark green, or bilious. They also go through periods of pain and decreased activity or lethargy, both of which alternate with other times when they seem just fine. Bloody, jelly-like stools are a late symptom of this condition.

You should call your pediatrician right away or go to an emergency room if you think that your baby might have intussusception. An air enema is commonly used for diagnosis and treatment, which will tell you if the child has an intussusception and in many cases will reduce it. Less commonly, surgery has to be done to reduce the blockage.

Intussusception is more common in boys and often occurs before a baby is two years old. However, it can occur in children up to about age six.

Constipation

Once you start solid foods, constipation can become a big problem. Even breastfeeding infants, who rarely get constipated, can begin to have hard stools when they start cereal. To help treat constipation, you can offer a few extra ounces of water or diluted apple juice. Or simply offer cereals with some fiber, such as barley or oatmeal. Although rice cereal is well tolerated by most infants, it doesn't have any fiber, so it can cause constipation.

Developmental Delays

Severe developmental delays are often obvious at any age. Most parents can recognize a problem if their two-month-old isn't making any noises or isn't looking at them at all. Motor delays, especially when they are mild, can often be harder to spot. You likely wouldn't notice or worry if your four-month-old wasn't holding her head up at a 90º angle, but you probably would start to worry if your seven-month-old wasn't rolling over or wasn't holding her head steady as she sat with support. Many parents anticipate the bigger milestones, such as sitting up and rolling over, so this time period is often when more developmental delays are noticed. Be sure to let your pediatrician know if there is anything that doesn't seem normal about your baby's development.