My son was 8lb 4.5oz. He wore them for about 2 weeks.

my son was 8lb 9oz and fit newborn for 3-4 weeks. but hes really long so that's why he grew out of them, not BC of his weight otherwise I think he would wear them longer

My daughter was 9lb 3oz and she wore them for a bit.

My son weighed 8 lbs. 8 oz. & he wore newborn for about a week. The pants fit him but the onesies were too snug in the belly area

My son was 7 pounds 8 ounces at birth. He wore them for 3 months!