When a wife of an Emperor gave birth, it was conventional that she and her nyobo wear all-white juni-hitoe (according to the "Murasaki Shikibu Nikki" [The Diary of Lady Murasaki]).
また天皇妃が出産する際には、妃はもちろん、その世話をする女房も白づくめの十二単をまとう慣例になっていた（『紫式部日記』）。