Wearing hairpins and skits are common practice for women in premodern China. Chaiqun as a compound also refers to women. In this context, it metaphorically refers to the newborn baby’s sex as being female. The specific mention of the gender nü is not necessary but to comply with the rhythm.
In the edition punctuated and collated by Guo Moruo (Shanghai guji chubanshe, 2002, p. 143), this phrase is yi chaiqun 一钗裙 [one with hairpin and skit], which gets rid of the redundant and has the same meaning.
A lady from the Qing dynasty wearing Han style chai [hairpin] and qun [long skirt].
Panel from The Twelve Beauties of Emperor Yongzheng 雍正十二美人圖.
