Komentaryo sa Genesis 20:18: Rashi, Radak, Sforno & Or HaChaim

בעד כל רחם GOD HAD CLOSED UP EVERY רחם — means had closed up every opening (of the body)

כי עצר עצר בעד כל רחם, among the women, and possibly also among the animals which were meant to give birth at that time. (as we quoted our sages as saying). In fact the Talmud says that even hens which lay eggs instead of producing live chicks from their bodies were equally affected.

כי עצר עצר ה' בעד כל רחם, to kill their (unborn) offspring if Avimelech would not display remorse and penitence. G’d had warned him specifically that not only his own life was at risk (verse 7)

'על דבר שרה וגו BECAUSE OF (literally, by the word of) SARAH — at Sarah’s bidding (Genesis Rabbah 52:13).