Constipation has a nasty habit of becoming a self-reinforcing cycle: a child has one painful poo, becomes frightened of pooing, holds it in, and the next one is even harder. Breaking that cycle early is the single most important thing you can do.
What it looks like
Fewer than three poos a week. Poo that is large and hard or looks like rabbit droppings. Straining or pain when pooing. Bleeding during or after a poo. In children over one, soiled pants can actually be a sign of constipation - liquid poo leaks around a hard blockage (overflow soiling). This is involuntary.
Common causes
Not enough fibre. Not enough fluids. Feeling anxious during potty training. Worry about nursery, a new sibling, or other changes. Too much milk intake in toddlers can also contribute.
What helps
Increase fruit and vegetables - pears, prunes, and plums are particularly effective. Make sure they're drinking enough water. Encourage regular toilet time, especially after meals when the bowel's natural reflexes are strongest. Make sure their feet are flat on the floor or on a step - this gets the pelvic floor into the right position.
Don't wait too long
See your GP rather than trying to manage at home for weeks. GPs commonly prescribe laxatives for children - these are safe and effective. NICE CG99 is clear that laxatives should be continued long enough for normal habits to become established, which may take several months. Stopping too early is the most common reason constipation returns.