Management of Pre-Existing Diabetes in Pregnancy

Management of Pre-Existing Diabetes in Pregnancy

Similar to recent trends of gestational diabetes (GDM), the prevalence of type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) has been increasing among women in reproductive ages.1 Pre-existing diabetes can pose maternal and fetal risks in pregnancy, but proper management can effectively prevent or reduce risks of complications. Management of GDM, a type of diabetes that develops as a result of pregnancy,2 is discussed separately.


Physiological Changes During Pregnancy

Early pregnancy is often marked by increased insulin sensitivity and lowered blood sugar levels compared to the nonpregnant state.1 Thus, women with T1DM often require lower doses of insulin and are at an increased risk of hypoglycemia during the first trimester due to decreased hypoglycemia awareness. During the late second trimester and early third trimester, insulin-mediated glucose uptake is significantly reduced to nurture the rapidly growing fetus.3 In healthy women, this insulin resistance is counteracted by a corresponding increase in insulin production by the pancreatic b-cells to maintain blood sugar levels. However, in women with pre-existing T2DM or T1DM, the b-cells do not sufficiently compensate,3 resulting in the need for increased insulin doses and dietary management to maintain glycemic targets.1


Effects of Diabetes on the Fetus

Unmanaged hyperglycemia during the periconceptual period and first trimester of pregnancy is known to be associated with fetal malformations and pregnancy loss in women with pre-existing diabetes and can inhibit placental growth.2 As maternal glucose is shared with the fetus across the placenta, maternal hyperglycemia typically promotes fetal hyperglycemia, which in turn promotes fetal hyperinsulinemia. Glucose use of the fetus increases with this process and can lead to macrosomia (weighing >4-4.5 kg) or fetuses that are large for gestational age (>90 percentile for gestational age), putting them at risk of hypoglycemia, shoulder dystocia, asphyxia, respiratory distress, and perinatal death.


Management of Diabetes Before & During Pregnancy


Preconception Counseling  All women with pre-existing diabetes are recommended to receive preconception counseling to be informed of the associated maternal and fetal risks and of the importance of achieving and maintaining glycemic targets.1 They should also be informed of the risk of developing and/or existing diabetic retinopathy progressing during pregnancy and the need for dilated eye exams and regular eye care.


Management – Healthy diets and regular moderate exercises are key to diabetes management even during pregnancy.1 Physical activities that involve contact sports, risk of fall, or heavy weights should, however, be avoided.4 Self-monitoring of blood sugar levels should be continued to maintain optimal levels. Target values are fasting plasma glucose of <95 mg/dL and 1-h postprandial glucose < 140 mg/dL or 2-h postprandial glucose <120 mg/dL. As A1C levels are typically lower in pregnancy, the optimal A1C target is <6% but can be relaxed to <7% to avoid hypoglycemia. Insulin is the preferred pharmaceutical treatment for both T1DM and T2DM during pregnancy as it is not known to cross the placenta.


Special Precautions – Women with T1DM should especially be informed of the increased risk of hypoglycemia in the first trimester due to decreased hypoglycemia awareness.1 Additionally, women with T1DM are at a greater risk of developing diabetic ketoacidosis (DKA) at lower blood glucose levels during pregnancy. It is recommended that they receive education on hypoglycemia and DKA prevention, detection, and treatment. Ketone strips should be prescribed. Women with T2DM have a risk of developing hypertension and other comorbidities that is as high as or higher than those with T1DM. Maintaining a target blood pressure of 110-135/85 mmHg can help reduce risks of fetal growth impairment.


1. American Diabetes Association Professional Practice Committee. 15. Management of Diabetes in Pregnancy: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2021;45(Supplement_1):S232-S243. doi:10.2337/dc22-S015
2. Egan AM, Dow ML, Vella A. A Review of the Pathophysiology and Management of Diabetes in Pregnancy. Mayo Clin Proc. 2020;95(12):2734-2746. doi:10.1016/j.mayocp.2020.02.019
3. Butler AE, Cao-Minh L, Galasso R, et al. Adaptive Changes in Pancreatic Beta Cell Fractional Area and Beta Cell Turnover in Human Pregnancy. Diabetologia. 2010;53(10):2167-2176. doi:10.1007/s00125-010-1809-6
4. Diabetes and Pregnancy | ADA. Accessed January 13, 2023.



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