American Diabetes association recommends start of Insulin
if the sugars are above the following levels in Gestational Diabetes
Fasting blood glucose
concentration >95 mg/dL (5.3 mmol/L)
One-hour postprandial blood glucose concentration >140 mg/dL (7.8 mmol/L)
Two-hour postprandial glucose concentration >120 mg/dL (6.7 mmol/L)
Since you have not mentioned at what time post breakfast you have measured you sugar... it may be difficult to judge , however in general values of >170 or >156/147 is high and we may require insulin.
I would advise you to consult a Diabetologist
/ Obstetrician and discuss this issue with him/her. I would also advise "Continous glucose monitoring" (CGM) a new tool for monitoring sugar continuously in patients with Gestational diabetes. Gestational Diabetes is an absolute indication for going for CGM .
Dr. Om Lakhani
http://www.healthcaremagic.com/doctors/dr-om-lakhani/60313 (online expert diabetes care consultantion)