Natyashastra
[दीर्घनिश्वसिते चैव जृम्भणे मोटने तथा । बिब्बोके च पुनः स्त्रीणां तद्विज्ञेयं प्रयोक्तृभिः ] ॥ २२९॥
The Nirbhugna breast is also used when there is a long sigh, yawning, stretching, and in women, it is expressed in moments of groaning or similar actions.
english translation
[dIrghanizvasite caiva jRmbhaNe moTane tathA । bibboke ca punaH strINAM tadvijJeyaM prayoktRbhiH ] ॥ 229॥
hk transliteration by Sanscript