The first two or three years, and the stream of practical questions that fills them. How often to bathe a newborn and with what. Whether a rash matters. Why a baby who was content with anyone at four months now objects to being handed over. What to do about a three-hour drive.
Most of those questions have short answers, and a surprising number of the answers amount to doing less than the shelves in any chemist would suggest. A healthy newborn needs plain water and nothing else on its skin for the first month. A baby does not need a bath every day. Most of the rashes that alarm new parents need no treatment at all — and one needs an ambulance, which is the single most useful thing on any of these pages.
Sleep is the exception to the territory, and deliberately so: it is gathered under sleep, with the material on babies and children under children's sleep, because anyone arriving with a sleep problem wants all of it together rather than scattered by age. The safer sleep guidance in particular is the most important thing in this whole section and it lives there.
Two general points, since they recur.
The first is how much has changed, and how recently. The advice on infant sleeping position changed within living memory and saved a great many lives. The advice on oils for newborn skin reversed after a trial found that the two oils everyone had been recommending for decades delayed the skin barrier forming. The legal minimum for rear-facing in a car is not what it was and is not what American sources still say. Anyone relying on what they were told with an earlier child is working from a different set of instructions.
The second is that a great deal of what gets recommended for babies on health grounds has very little behind it. That is not a reason to stop doing any of it — a quiet quarter of an hour of being stroked is a good thing in a baby's day whatever the trials say. It is a reason to be wary of anything sold on the promise of better sleep, fewer colds or faster development, and to treat the unglamorous items as the ones that count.