She mentioned that to the Messenger of Allah ﷺ, and he said, "Tell her to perform ghusl and then enter the state of ihram."
أخبرنا محمد بن سلمة والحارث بن مسكين قراءة عليه وأنا أسمع واللفظ له عن ابن القاسم قال حدثني مالك عن عبد الرحمن بن القاسم عن أبيه عن أسماء بنت عميس أنها ولدت محمد بن أبي بكر الصديق بالبيداء
ذلك لرسول الله ﷺ فقال مرها فلتغتسل ثم لتهل
[Its isnad is sahih] It was narrated by Ahmad, 6/369, from the hadith of Malik, by this same chain. It is also found in Muwatta (Yahya), 1/322, and in Kubra, no. 3643. It was also narrated by Muslim, no. 1209/109, through another route, from Abdul-Rahman bin Qasim, from his father, from Ayesha, by this same chain.