John Gill Commentary Genesis 38:27

"And it came to pass in the time of her travail, that, behold, twins were in her womb." — Genesis 38:27 (ASV)

And it came to pass in the time of her travail. When her time to bring forth was come, and her pains were on her, and her midwife with her: that, behold, twins [were] in her womb; which the midwife could discover before the birth of either.