Leviticus Rabbah 14:9 — Sefaria version 'The Sefaria Midrash Rabbah, 2022' (CC-BY) (CC BY)
Rabbi Abahu said: The Holy One blessed be He performed a great favor for the woman in this world in that He did not begin formation of the fetus with sinews and bones. Had He so begun, it would have breached her belly and emerged. Although in this world, the woman gives birth in pain, in the future, what is written? “Before she begins labor, she will give birth; before a pang comes to her, [she will deliver a male child]” (Isaiah 66:7).
Reproduced in full. Translation: Sefaria version 'The Sefaria Midrash Rabbah, 2022' (CC-BY) (CC BY).
Why Pitre cites it
'In this world a woman bears children with pain, but of the time to come…' — no birth pangs in the world to come, with Isaiah 66:7 as proof.
Notes
Only the closing statement of Rabbi Abahu extracted (14:9 is long; the earlier part is the Beit Shammai/Beit Hillel dispute on embryology). Sefaria wording: 'Although in this world, the woman gives birth in pain, in the future, what is written? "Before she begins labor, she will give birth ..." (Isaiah 66:7)' — key phrase given as 'In this world a woman bears children with pain, but in the time to come...' (Soncino-style).