Constipation refers to the hardness of the stools and the difficulty passing them, and not so much the frequency of bowel movements. If your baby is not bloated or colicky, and isn't straining to have a bowel movement, it could just be that this is his normal intestinal pattern. Still, nine days without a bowel movement is a bit long. I suggest you keep track of his feeding patterns for a while. See if you can encourage him to have a stool more often. Here's how:
Offer extra water. If your baby is formula-fed, offer her an extra bottle of water each day. (Breastfed infants seldom need extra water.) I call this "drinking to go." Lack of fluids is one of the most common contributors to constipation. When a baby is not drinking enough, his colon steals water from the waste material and gives it to the body. This causes the stools to be water-deprived or hard.
Consider changing formulas. Formula-fed infants tend to have fewer and firmer stools. Ask your doctor about experimenting with different formulas. At three months, most infants will have a bowel movement at least every other day, and some will have several a day. A different formula could help your baby have a comfortable bowel movement at least every few days.
Delay solids. Babies who are prone to constipation often experience problems with regular bowel movements when switching to solids. Holding off awhile will allow your child's digestive system to mature somewhat. When you introduce solids, start with stool-softening foods. Remember the four pureed P's: peaches, pears, plums, and prunes. And try barley, instead of the more-constipating rice cereal.
Ease the passage. If your baby starts to grunt and strain to have a bowel movement, get some glycerin suppositories from your pharmacy. Insert the suppository at least an inch up into his rectum and hold Baby's buttocks together for a few minutes until it dissolves. You can also squirt a dropper of liquid glycerin into the rectum at the first sign of straining. Use these once a day for a couple weeks, until you've managed to soften the stools by dietary means. Liquid glycerin will also help heal tears in the rectum caused by constipation — fresh blood on a diaper is a sure sign of these tears.
Consider natural laxatives. If extra water doesn't seem to work, other dietary changes could help in babies as young as 4-months-old. Diluted prune juice (one tablespoon in eight ounces of water) is a time-tested remedy. We use flax oil in our pediatric practice. Besides being a good source of extra omega-3 fats, flax oil is a natural laxative. Add one teaspoon to one of your baby's bottles once a day. Toddlers can have as much as a tablespoon a day.
Constipation is very uncomfortable for infants and it becomes a self-perpetuating problem. The more constipated a baby gets, the more it stretches the colon, which further aggravates constipation. This is why it's important to identify and treat constipation early. The number of stools and their nature varies tremendously from baby to baby, so primarily you want to watch for any signs of straining. I remember when one of our infants became very constipated and needed all the above treatments. One day as Martha was helping Matthew "deliver" a hard stool, she said: "I feel like a midwife."