From Sahih Muslim (Hadith 2237):
Samura b. Jundub said:I was a young boy during the time of the Prophet (ﷺ) and I retained in my mind (what I learnt from him), and nothing restrained me from speaking except the fact that there were persons far more advanced in age than I. Verily, I said prayer behind the Messenger of Allah (ﷺ) over a woman who had died in the state of delivery, and the Messenger of Allah (ﷺ) stood up to say prayer in front of the middle part of her body. And in the tradition narrated on the authority of Ibn Muthanna the words are:" (The Holy Prophet) stood in the middle part of her body for offering prayer for her
Reference: Muslim 2237