Oje, ich wachse!

The Wonder Weeks: A Stress-Free Guide to Your Baby's Behavior is a book with advice to parents about child development by physical anthropologist Hetty van de Rijt and ethologist and developmental psychologist Frans Plooij. Their daughter Xaviera Plas-Plooij is a third author of recent editions. It was first published in English in 2003 as the translation of the 1992 Dutch book Oei, ik groei! The book claims that the cognitive development of babies occurs in predictably timed stages. Ever since the systematic study of child development began at the beginning of the 20th century researchers have disagreed whether this is gradual or in punctuated stages. Some figures in the child development field have objected that sleep regressions are not so predictable. A chapter on sleep was added to the 6th edition in 2019. The publisher has produced a mobile app based on the book.