A constipated baby's stools will be hard or pellet-like. If baby's poop is soft — even if it's his first poop in a week or more — it's not constipation. Some babies can simply hold more poop than others and keep it in longer. This isn't a cause for concern.
Constipation is super-rare in exclusively breastfed babies. If baby is supplemented with formula or has started solids, constipation is more likely. To handle true constipation, your doctor might recommend adding a little water or clear fruit juice to baby's diet or — if baby is eating solids — a bit of high-fiber baby food (like barley cereal, pears or prunes). You can dab a little water-based lubricant around baby's anus to make pooping more comfortable. But whatever you do, DON'T treat baby with laxatives, enemas or mineral oil.