Getting induced help!

Samantha
My doc informed me today that due to my gestational diabetes, even though baby is measuring in the 45th percentile , average size for this gestation, that they will induce me between 38&39 weeks, but they won't let me go past 39weeks. They don't want the baby to get too big, or risk still birth. My sister is insisting I refuse to be induced until 39wks, any other mamas going through the same? Or think I should refuse? My sis is training to become a midwife & says its puts me and the baby at risk being induced at 38weeks