In this specific instance the KJV is not the best at illustrating the topic at hand and many other versions directly indicate pain. 16 To the woman he said, “I will make your pains in childbearing very severe; with painful labor you will give birth to children. Your desire will be for your husband, and he will rule over you.” I generally despise people who start "going to the Greek" (Hebrew in this case) but ʿiṣṣāḇôn is what it is (sorrow/toil). What's the difference between working out in a field and toiling out in the field? Does one suck way more? Does a cow appear to toil while giving birth? Does a human woman appear to toil while giving birth? Definitely something going on there that isn't represented anywhere near as well as "sorrow".