Below you can find ADA standards on proper A1c targets, blood pressure range, retinopathy monitoring and medications used in preexisting and gestational diabetes. The preferred medications during pregnancy are insulin, metformin and glyburide.

Recommendations are listed below with slightly modified wording for easier and succinct reading:

Diabetes Care

ADA Guidelines

January 2017

Preexisting Diabetes

Lifestyle change is an essential component of management of gestational diabetes mellitus and may suffice for the treatment for many women. Medications should be added if needed to achieve glycemic targets.
Insulin is the preferred medication for treating hyperglycemia in gestational diabetes mellitus, as it does not cross the placenta to a measurable extent. Metformin and glyburide may be used, but both cross the placenta to the fetus, with metformin likely crossing to a greater extent than glyburide. All oral agents lack long-term safety data.
Metformin, when used to treat polycystic ovary syndrome and induce ovulation, need not be continued once pregnancy has been confirmed.

General Principles

Potentially teratogenic medications (ACE inhibitors, statins, etc.) should be avoided in sexually active women of childbearing age who are not using reliable contraception.
Due to increased red blood cell turnover, A1C is lower in normal pregnancy than in normal nonpregnant women. The A1C target in pregnancy is 6–6.5%; <6% may be optimal if this can be achieved without significant hypoglycemia, but the target may be relaxed to <7% if necessary to prevent hypoglycemia.
In pregnant patients with diabetes and chronic hypertension, blood pressure targets of 120–160/80–105 mmHg are suggested in the interest of optimizing long-term maternal health and minimizing impaired fetal growth

Preconception counseling should address the importance of glycemic control as close to normal as is safely possible, ideally A1C <6.5% to reduce the risk of congenital anomalies.
Women with preexisting type 1 or type 2 diabetes who are planning pregnancy or who have become pregnant should be counseled on the risk of development and/or progression of diabetic retinopathy. Dilated eye examinations should occur before pregnancy or in the first trimester, and then patients should be monitored every trimester and for 1 year postpartum as indicated by degree of retinopathy and as recommended by the eye care provider.

Gestational Diabetes Mellitus

Lifestyle change is an essential component of management of gestational diabetes mellitus and may suffice for the treatment for many women. Medications should be added if needed to achieve glycemic targets.
Insulin is the preferred medication for treating hyperglycemia in gestational diabetes mellitus, as it does not cross the placenta to a measurable extent. Metformin and glyburide may be used, but both cross the placenta to the fetus, with metformin likely crossing to a greater extent than glyburide. All oral agents lack long-term safety data.
Metformin, when used to treat polycystic ovary syndrome and induce ovulation, need not be continued once pregnancy has been confirmed.

General Principles

Potentially teratogenic medications (ACE inhibitors, statins, etc.) should be avoided in sexually active women of childbearing age who are not using reliable contraception.
Due to increased red blood cell turnover, A1C is lower in normal pregnancy than in normal nonpregnant women. The A1C target in pregnancy is 6–6.5%; <6% may be optimal if this can be achieved without significant hypoglycemia, but the target may be relaxed to <7% if necessary to prevent hypoglycemia.
In pregnant patients with diabetes and chronic hypertension, blood pressure targets of 120–160/80–105 mmHg are suggested in the interest of optimizing long-term maternal health and minimizing impaired fetal growth