Yesterday I was taken aback by reading about a metric baby. It was in a museum exhibit about pregnancy and babies. The original Spanish said the foetus, at a particular stage of its development “tenía medidas milimétricas” [literally “had millimetric measurements/dimensions] meaning it was just a few millimetres long. The translator wrote that it “was measured in millimeters”, implying that it would have been inappropriate to measure it in inches or some other non-metric units.
Perhaps babies now come into the world knowing they have been born into a society which uses the Système International!