Albert Barnes Commentary Exodus 1:16

"and he said, When ye do the office of a midwife to the Hebrew women, and see them upon the birth-stool; if it be a son, then ye shall kill him; but if it be a daughter, then she shall live." — Exodus 1:16 (ASV)

Upon the stools - Literally, “two stones.” The word denotes a special seat, such as is represented on monuments of the 18th Dynasty, and is still used by Egyptian midwives.