Following her first pregnancy she was told she was no longer diabetic

A 29-year-old woman has just found out she is pregnant for the second time. Her first pregnancy was complicated by gestational diabetes. Following her first pregnancy she was told she was no longer diabetic. What is the most appropriate management?

A. Do oral glucose tolerance test at usual 24-28 weeks
B. Start metformin and do oral glucose tolerance test at 12-14 weeks
C. Do oral glucose tolerance test at booking visit
D. Do oral glucose tolerance test at 16-18 weeks