Pregnancy makes glycemic control more difficult in preexisting type 1 (insulin-dependent) and type 2 (non–insulin-dependent) diabetes but does not appear to exacerbate diabetic retinopathy, nephropathy, or neuropathy (1).
Gestational diabetes occurs in approximately 4% of pregnancies, but the rate is above average in people of certain ethnicities (non-Hispanic Asian/Pacific Islander and Hispanic/Latina) (2). Women with gestational diabetes are at increased risk of type 2 diabetes in the future.
Guidelines for managing diabetes mellitus during pregnancy are available from the American College of Obstetricians and Gynecologists (ACOG [1, 3]).
Risks of diabetes during pregnancy
Diabetes during pregnancy increases fetal and maternal morbidity and mortality. Neonates are at risk of respiratory distress, hypoglycemia, hypocalcemia, hyperbilirubinemia, polycythemia, and hyperviscosity.
Poor control of preexisting (pregestational) or gestational diabetes during organogenesis (up to about 10 weeks gestation) increases risk of the following:
Major congenital malformations
Poor control of diabetes later in pregnancy increases risk of the following:
Fetal macrosomia (usually defined as fetal weight > 4000 grams or > 4500 grams at birth)
However, gestational diabetes can result in fetal macrosomia even if blood glucose is kept nearly normal.
General references
1. Committee on Practice Bulletins—Obstetrics: ACOG Practice Bulletin No. 201: Clinical management guidelines for obstetrician-gynecologists: Pregestational diabetes mellitus. Obstet Gynecol 132 (6):e228–e248, 2018. doi: 10.1097/AOG.0000000000002960
2. Shah NS, Wang MC, Freaney PM, et al: Trends in Gestational Diabetes at First Live Birth by Race and Ethnicity in the US, 2011-2019. JAMA 326(7):660-669, 2021. doi:10.1001/jama.2021.7217
3. Committee on Practice Bulletins—Obstetrics: ACOG Practice Bulletin No. 190: Gestational diabetes mellitus. Obstet Gynecol 131 (2):e49–e64, 2018. doi: 10.1097/AOG.0000000000002501
Diagnosis of Diabetes Mellitus in Pregnancy
Oral glucose tolerance test (OGTT) or a single plasma glucose measurement (fasting or random)
The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for gestational diabetes, typically at 24 to 28 weeks gestation (1). An OGTT is recommended, but the diagnosis can probably be made based on a fasting plasma glucose of > 126 mg/dL (> 6.9 mmol/L) or a random plasma glucose of > 200 mg/dL (> 11 mmol/L).
The recommended screening method has 2 steps. The first is a screening test with a 50-g oral glucose load and a single measurement of the glucose level at 1 hour. If the 1-hour glucose level is > 130 to 140 mg/dL (> 7.2 to 7.8 mmol/L), a second, confirmatory 3-hour test is done using a 100-g glucose load (see table Glucose Thresholds for Gestational Diabetes Using a 3-hour Oral Glucose Tolerance Test ).
Most organizations outside the United States recommend a single-step, 2-hour test.
Glucose Thresholds for Gestational Diabetes Using a 3-hour Oral Glucose Tolerance Test*
Organization | Fasting mg/dL (mmol/L) | 1-hour mg/dL (mmol/L) | 2-hour mg/dL (mmol/L) | 3-hour mg/dL (mmol/L) |
|---|---|---|---|---|
Carpenter and Coustan | 95 (5.3) | 180 (10) | 155 (8.6) | 140 (7.8) |
National Diabetes Data Group | 105 (5.8) | 190 (10.6) | 165 (9.2) | 145 (8) |
* A 100-g glucose load is used. | ||||
Diagnosis reference
1. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol 131(2):e49-e64, 2018. doi:10.1097/AOG.0000000000002501
Treatment of Diabetes Mellitus in Pregnancy
Close monitoring
Tight control of blood glucose
Management of complications
Preconception counseling and optimal control of diabetes before, during, and after pregnancy minimize maternal and fetal risks, including congenital malformations (1). Because malformations may develop before pregnancy is diagnosed, the need for constant, strict control of glucose levels is stressed to women who have diabetes and who are considering pregnancy (or who are not using contraception).
To minimize risks, clinicians should do all of the following:
Involve a diabetes team (eg, physicians, nurses, nutritionists, social workers) and a pediatrician
Promptly diagnose and treat complications of pregnancy, no matter how trivial
Plan for delivery and have an experienced pediatrician present
Ensure that neonatal intensive care is available
In regional perinatal centers, specialists in management of diabetic complications are available.
During pregnancy
Treatment can vary, but some general management guidelines are useful (see tables Management of Type 1 Diabetes During Pregnancy, Management of Type 2 Diabetes During Pregnancy, and Management of Gestational Diabetes During Pregnancy).
Women with type 1 or 2 should monitor their blood glucose levels at home. During pregnancy, normal fasting blood glucose levels are about 76 mg/dL (4.2 mmol/L).
Goals of treatment are
Fasting blood glucose levels at < 95 mg/dL (< 5.3 mmol/L)
2-hour postprandial levels at ≤ 120 mg/dL (≤ 6.6 mmol/L)
No wide blood glucose fluctuations
Glycosylated hemoglobin (HbA1c) levels at < 6.5%
Management of Type 1 Diabetes Mellitus* During Pregnancy
Time Frame | Measures |
|---|---|
Before conception | Glycemic control Risk is lowest if HbA1c levels are ≤ 6.5% at conception.† Evaluation includes
|
Prenatal | Prenatal visits begin as soon as pregnancy is confirmed. Frequency of visits is determined by degree of glycemic control. Diet should be individualized according to ADA guidelines and coordinated with insulin administration. Three meals and three snacks/day are recommended, with emphasis on consistent timing. Women are instructed in and should do blood glucose self-monitoring. Women should be cautioned about the dangers of hypoglycemia during exercise and at night. HbA1c level should be checked every trimester. Antenatal testing with the following should be done from 32 weeks to delivery (or earlier if indicated):
Amount and type of insulin should be individualized. In the morning, two thirds of the total dose (60% NPH, 40% regular) is taken; in the evening one third (50% NPH, 50% regular) is taken. Or, women can take long-acting insulin once or twice a day and insulin aspart immediately before breakfast, lunch, and dinner.‡ |
During labor and delivery | Vaginal delivery at term is possible if women have documented dating criteria and good glycemic control. Cesarean delivery should be reserved for obstetric indications or fetal macrosomia (> 4500 g), which increases risk of shoulder dystocia. The optimal timing of delivery relies on balancing the risk of fetal death with the risks of preterm birth. Early delivery (36 to38 6/7 weeks of gestation, or even earlier) may be indicated in some patients with complications such as, vasculopathy, nephropathy, poor glucose control, or a prior stillbirth. Women with well-controlled diabetes with no other comorbidities may be managed expectantly to 39 0/7 weeks to 39 6/7 weeks of gestation as long as antenatal testing remains reassuring. During delivery, a constant low-dose insulin infusion is usually preferred, and the usual subcutaneous administration of insulin is stopped. If induction is planned, the usual evening long-acting insulin dose is given on the day before induction. Postpartum and continuing diabetes care should be arranged. Postpartum insulin requirements may decrease by up to 50%. |
* Guidelines are only suggested; marked individual variations require appropriate adjustments. | |
† Normal values may differ depending on laboratory methods used. | |
‡ Some hospital programs recommend up to 4 insulin injections daily. Continuous subcutaneous insulin infusion, which is labor-intensive, can sometimes be given in specialized diabetes clinics. | |
ADA = American Diabetes Association; ECG = electrocardiography; HbA1c = glycosylated hemoglobin; NPH = | |
Management of Type 2 Diabetes Mellitus* During Pregnancy
Time Frame | Measures |
|---|---|
Before conception | Glycemic control Risk is lowest if HbA1c levels are ≤ 6.5% at conception.† Weight loss is encouraged if BMI is > 27 kg/m2. The diet should be low in fat, relatively high in complex carbohydrates, and high in fiber. Exercise is encouraged. |
Prenatal | For women with overweight, diet and caloric intake are individualized and monitored to avoid weight gain of more than about 6.8–11.3 kg (> 15–25 lb) or, if they are obese, more than about 5–9.1 kg (> 11–20 lb). Moderate walking after meals is recommended. Women are instructed in and should do blood glucose self-monitoring. The 2-hour postbreakfast blood glucose level is checked weekly at clinic visits if possible. HbA1c level should be checked every trimester. Antenatal testing with the following should be done from 32 weeks to delivery (or earlier if indicated):
Amount and type of insulin is individualized. For women with obesity, short-acting insulin is taken before each meal. For women who are not obese, two thirds of the total dose (60% NPH, 40% regular) is taken in the morning; one third (50% NPH, 50% regular) is taken in the evening. Or, women can take long-acting insulin once or twice a day and insulin aspart immediately before breakfast, lunch, and dinner. |
During labor and delivery | Management is the same as for type 1 (see table Management of Type 1 Diabetes Mellitus During Pregnancy). |
* Guidelines are only suggested; marked individual variations require appropriate adjustments. | |
† Normal values may differ depending on laboratory methods used. | |
BMI = body mass index; HbA1c = glycosylated hemoglobin; NPH = | |
Management of Gestational Diabetes During Pregnancy
Time Frame | Measures |
|---|---|
Before conception | Women who have had gestational diabetes in previous pregnancies should try to reach or maintain a normal weight and engage in modest exercise. The diet should be low in fat, relatively high in complex carbohydrates, and high in fiber. Fasting plasma glucose and HbA1c levels should be checked. |
Prenatal | Diet and caloric intake are individualized and monitored to prevent weight gain of more than about 6.8–11.3 kg (> 15–25 lb) or, if women are obese, more than about 5–9.1 kg (> 11–20 lb). Moderate exercise after meals is recommended. Antenatal testing with the following should be done from 32 weeks to delivery (or earlier if indicated):
≥ 2 weeks. Amount and type of insulin should be individualized. For women with obesity, short-acting insulin is taken before each meal. For women who are not obese, two thirds of the total dose (60% NPH, 40% regular) is taken in the morning; one third (50% NPH, 50% regular) is taken in the evening. Or, women can take long-acting insulin once or twice a day and insulin aspart immediately before breakfast, lunch, and dinner. |
During labor and delivery | Vaginal delivery at term is possible if women have a well-documented delivery date and good diabetic control. Cesarean delivery should be reserved for obstetric indications or fetal macrosomia (> 4500 g), which increases risk of shoulder dystocia. In women with gestational diabetes that is controlled with diet and exercise only, delivery should occur between 39 and 40 6/7 weeks of gestation. For women with gestational diabetes that is well controlled by medications (A2GDM), delivery is recommended from 39 0/7 weeks to 39 6/7 weeks of gestation. Expert opinion supports earlier delivery for women with poorly controlled gestational diabetes; however, recommendations about timing of delivery lack specific guidance. Decision making may be guided by consultation with a maternal fetal medicine specialist. |
HbA1c = glycosylated hemoglobin; NPH = | |
Insulin is the traditional treatment of choice because it cannot cross the placenta and provides more predictable glucose control; it is used for types 1 and 2 diabetes and for some women with gestational diabetes. Human insulin is used if possible because it minimizes antibody formation. Insulininsulin< 40 mg/dL [< 2.2 mmol/L]) occurs.
Pearls & Pitfalls
Oral hypoglycemic drugsinsulin for women with gestational diabetes. For women with type 2 diabetes before pregnancy, data for use of oral drugs during pregnancy are scant; insulin is most often preferred. Oral hypoglycemics taken during pregnancy may be continued postpartum during breastfeeding, but the infant should be closely monitored for signs of hypoglycemia.
Management of complications
Although diabetic retinopathy, nephropathy, and mild neuropathy are not contraindications to pregnancy, they require preconception counseling and close management before and during pregnancy.
Retinopathy requires that an ophthalmologic examination be done every trimester. If proliferative retinopathy is noted at the first prenatal visit, photocoagulation should be used as soon as possible to prevent progressive deterioration.
Nephropathy, particularly in women with renal transplants, predisposes to gestational hypertension. Risk of preterm delivery is higher if maternal renal function is impaired or if transplantation was recent. Prognosis is best if delivery occurs ≥ 2 years after transplantation.
Congenital malformations of major organs are predicted by elevated HbA1c levels at conception and during the first 8 weeks of pregnancy. If the level is ≥ 8.5% during the 1st trimester, risk of congenital malformations is significantly increased, and targeted ultrasonography and fetal echocardiography are done during the 2nd trimester to check for malformations (2). If women with type 2 diabetes take oral hypoglycemic drugs during the 1st trimester, fetal risk of congenital malformations is unknown (see table Some Drugs With Adverse Effects During Pregnancy).
Labor and delivery
Certain precautions are required to ensure an optimal outcome.
Timing of delivery depends on fetal well-being. Women are told to count fetal movements during a 60-minute period daily (fetal kick count) and to report any sudden decreases to the obstetrician immediately. Antenatal testing is begun at 32 weeks; it is done earlier if women have severe hypertension or a renal disorder or if fetal growth restriction is suspected. Amniocentesis to assess fetal lung maturity may be necessary for women with the following:
Obstetric complications in past pregnancies
Inadequate prenatal care
Uncertain delivery date
Poor glucose control
Poor adherence to therapy
Type of delivery is usually spontaneous vaginal delivery at term. Risk of stillbirth and shoulder dystocia increases near term. Thus, if labor does not begin spontaneously by 39 weeks, induction is often necessary. Dysfunctional labor, fetopelvic disproportion, or risk of shoulder dystocia may make cesarean delivery necessary.
Blood glucose levels are best controlled during labor and delivery by a continuous low-dose insulin infusion. If induction is planned, women eat their usual diet the day before and take their usual insulin dose. On the morning of labor induction, breakfast and insulin insulin infusion rate is determined by capillary glucose level. Insulin dose is determined as follows:
Initially: 0 units for a capillary level of < 80 mg/dL (< 4.4 mmol/L) or 0.5 units/hour for a level of 80 to 100 mg/dL (4.4 to 5.5 mmol/L)
Thereafter: Increased by 0.5 units/hour for each 40-mg/dL (2.2-mmol/L) increase in glucose level over 100 mg/dL up to 2.5 units/hour for levels > 220 mg/dL (> 12.2 mmol/L)
Every hour during labor: Measurement of glucose level at bedside and adjustment of dose to keep the level at 70 to 120 mg/dL (3.8 to 6.6 mmol/L)
If the glucose level is significantly elevated: Possibly additional bolus doses
For spontaneous labor, the procedure is the same, except that if intermediate-acting insulin was taken in the previous 12 hours, the insulin dose is decreased. For women who have fever, infection, or other complications and for women with obesity who have type 2 and have required > 100 units of insulin/day before pregnancy, the insulin dose is increased.
Postpartum
After delivery, loss of the placenta, which synthesizes large amounts of insulin antagonist hormones throughout pregnancy, decreases the insulin requirement immediately. Thus, women with gestational diabetes and many of those with type 2 require no insulin postpartum. For women with type 1, insulin requirements decrease dramatically but then gradually increase after about 72 hours.
During the first 6 weeks postpartum, the goal is tight glucose control. Glucose levels are checked before meals and at bedtime. Breastfeeding is not contraindicated but may result in neonatal hypoglycemia if oral hypoglycemics are taken. Women who have had gestational diabetes should have a 2-hour oral glucose tolerance test with 75 g of glucose at 6 to 12 weeks postpartum to determine whether diabetes has resolved.
Treatment references
1. American College of Obstetricians and Gynecologists' Committee on Practice Bulletins—Obstetrics. ACOG Practice Bulletin No. 201: Pregestational Diabetes Mellitus. Obstet Gynecol 132(6):e228-e248, 2018. doi:10.1097/AOG.0000000000002960
2. Miller E, Hare JW, Cloherty JP, et al: Elevated maternal hemaglogin A1c in early pregnancy and major congenital anomalies in infants of diabetic mothers. N Engl J Med 304 (22):1331–1334, 1981. doi: 10.1056/NEJM198105283042204
Key Points
Diabetes in pregnancy increases risk of fetal macrosomia, shoulder dystocia, preeclampsia, cesarean delivery, stillbirth, and, if preexisting or gestational diabetes is poorly controlled during organogenesis, major congenital malformations and spontaneous abortion.
Screen all pregnant women for gestational diabetes using an oral glucose tolerance test.
Involve a diabetes team if available, and aim to keep fasting blood glucose levels at < 95 mg/dL (< 5.3 mmol/L) and 2-hour postprandial levels at ≤ 120 mg/dL (≤ 6.6 mmol/L).
Begin antenatal testing at 32 weeks and deliver by 39 weeks.
Adjust insulin dose immediately after delivery of the placenta.
