It's probably the worst thing about motherhood. And it's a thing they don't warn you of – those upbeat parenting manuals.
The knock drags you from slumber in the small hours. 'I woke with another headache,' they wail. The wafts on the landing tell you the rest. Turgid with sleep you prioritise. Fill a bath for the vomit-soaked invalid; fill a sink for the foul-clotted bedding. You shampoo. You launder. You tuck them up, soap-scented, in clean sheets and you soothe them into serenity.
Then, irreversibly awake, you return to bed and you realise: the power to relieve childish grief is probably the best thing about motherhood.