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Year : 2022  |  Volume : 1  |  Issue : 1  |  Page : 31-36

Blood glucose management in gestational diabetes: A clinician's review

Department of Diabetes and Endocrinology, Chellaram Diabetes Institute, Pune, Maharashtra, India

Date of Submission08-Oct-2021
Date of Decision30-Oct-2021
Date of Acceptance30-Oct-2021
Date of Web Publication7-Jan-2022

Correspondence Address:
Kumaran S Suganthi
Chellaram Diabetes Institute, Lalani Quantum, Pune Bangalore Highway, Bavdhan, Pune - 411 021, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/cdrp.cdrp_2_21

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The prevalence of gestational diabetes mellitus (GDM) has been increasing globally and in India too, because of urbanization and the increasing occurrence of obesity. The management of GDM poses a clinical challenge, and this article focuses on its diagnosis and treatment. In India, screening of all pregnant women is recommended at the first antenatal visit and then repeat screening at 24–28 weeks of gestation if the initial screen is normal. Early intervention with counseling, glucose monitoring, diet, and exercise to achieve good glucose control could reduce both the maternal and fetal complications associated with hyperglycemia in pregnancy. The majority of cases of GDM may be managed by lifestyle modifications alone. Metformin may be prescribed as an alternative to insulin as per certain guidelines, though insulin remains the cornerstone of pharmacotherapy. Long-acting insulin detemir and short-acting insulin analogs such as insulin lispro or aspart are safe in pregnancy and help with control of blood glucose. Good glycemic control, achieved by lifestyle measures, monitoring, and medications when needed, may help achieve the goal of a successful pregnancy outcome.

Keywords: Gestational diabetes, glucose management, insulin aspart, insulin detemir, metformin

How to cite this article:
Suganthi KS, Sarkar NS. Blood glucose management in gestational diabetes: A clinician's review. Chron Diabetes Res Pract 2022;1:31-6

How to cite this URL:
Suganthi KS, Sarkar NS. Blood glucose management in gestational diabetes: A clinician's review. Chron Diabetes Res Pract [serial online] 2022 [cited 2023 Mar 29];1:31-6. Available from: https://cdrpj.org//text.asp?2022/1/1/31/335255

  Introduction Top

Gestational diabetes mellitus (GDM) is generally defined as hyperglycemia with onset or initial recognition during pregnancy. With the increase in urbanization and a simultaneous rise in obesity, the prevalence of GDM is increasing. GDM may affect between 5 and 8 million pregnant women in India annually.[1] In general, the prevalence of GDM may range from 4% to 18%, and it is approximately 7% higher in urban versus rural areas.[1],[2] Treatment of GDM improves the pregnancy outcomes for both the mother and baby.[3] The treatment of GDM is mainly lifestyle modification as only about 30% may require pharmacological treatment.[4] This review focuses on clinical aspects of diagnosing and managing gestational diabetes.

  Screening Top

Conventionally, GDM is detected during 24–28 weeks of pregnancy. Universal screening for glucose intolerance is recommended for all Indian pregnant women as the relative risk of developing GDM in Indian women is 11-fold higher when compared to Caucasian women.[5] Hence, screening of all women from high-risk ethnicity groups (or women with one risk factor or more from high-risk ethnicity groups) must be offered during the first antenatal visit itself.[6],[7] The risk factors include obesity, family history of diabetes in the first-degree relatives, and previous history of gestational diabetes.

The screening test called 2-h oral glucose tolerance test (OGTT) is performed, in the morning after an overnight fast of at least 8 h, with 75 g of glucose at the first antenatal visit. If the OGTT results are normal, a second OGTT is performed at 24–28 weeks.

For screening, it is important to select the criteria that are most suitable to the patient population and regional needs. For instance, the Diabetes in Pregnancy Study Group of India (DIPSI) criteria is very simple to implement as it does not require fasting. Therefore, it is suitable to be used in remote areas where women find it difficult to travel long distances to visit in the fasting state. On the other hand, the American Diabetes Association (ADA) criteria is based on sound evidence and is generally accepted internationally.

  Diagnosis Top

The Diabetes in Pregnancy Study Group of India criteria

DIPSI criteria for diagnosis of gestational diabetes, after consumption of 75 g of oral glucose, irrespective of the fasting state is shown in [Table 1].[8]
Table 1: Diabetes in pregnancy study group of India criteria

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Since the test is done nonfasting, without considering meal timings, it can be considered when it is difficult for patients to do a fasting OGTT.[9],[10]

The American Diabetes Association-2019 – One-step strategy

In 2008, Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study established the association between mild hyperglycemia and maternal and fetal outcomes such as large for gestation babies (>90%), cesarean sections, neonatal hypoglycemia, preeclampsia, and preterm delivery in a cohort of about 25,000 pregnancies. The International Association of Diabetes and Pregnancy Study Groups panel further reviewed the HAPO study results and recommended two-phase strategy for diagnosis of GDM. The first phase involves testing either fasting plasma glucose, glycosylated hemoglobin (HbA1c), or random blood glucose at the first antenatal visit. If normal, then the second phase involves 2-h OGTT performed at 24–28 weeks of gestation. This recommendation has also led to the ADA criteria for diagnosis of GDM.

As per ADA 2019, for the diagnosis of GDM, 75 g of OGTT is performed at 24–28 weeks of gestation. After 8 h of overnight fast, fasting plasma glucose is checked. Then, 75 g of oral glucose is given. Plasma glucose value is tested 1 h and 2 h post this 75 g of glucose consumption. The diagnosis of GDM is made, when one of the following criteria is met as shown in [Table 2].[11]
Table 2: American Diabetes Association criteria for diagnosis of gestational diabetes mellitus - oral glucose tolerance test

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The glycemic targets during pregnancy as per the ADA 2019, “Standards of Medical Care in Diabetes” is shown in [Table 3].
Table 3: Glycemic targets in pregnancy

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Either 1-h or 2-h postprandial (PP) glucose levels may be monitored. However, in general, 1-h PP is preferred in pregnancy.[12]

  Maternal and Fetal Complications in Gestational Diabetes Mellitus Top

The goal of management of GDM is to avoid maternal–fetal complications. Major congenital anomalies occur in 6%–12% of diabetic pregnancies. If the HbA1c can be kept at around 5%–6%, the fetal malformation rate is close to normal pregnancies (2%–3%). However, if HbA1c is as high as 10%, then a fetal anomaly rate as high as 20%–25% may be encountered.[13] HbA1c is widely used as a marker of type 2 diabetes and also predicts maternofetal outcome. However, its efficacy in the diagnosis of GDM requires further research. In general, HbA1c when used for diagnosing GDM has low specificity but high sensitivity. However, HbA1c can predict future occurrence of type 2 diabetes in women with GDM. HbA1c cannot be an alternative to OGTT for diagnosis of GDM, and any HbA1c result in pregnant women with suspected GDM should be interpreted only in the light of an accompanying OGTT result.[14]

Maternal complications of GDM include preeclampsia, polyhydramnios, abruptio placenta, and preterm delivery. There is also an increased chance of cesarean delivery. Women who have had GDM are much more likely to develop type 2 DM later in life.[15] There is a higher risk of developing GDM again in future pregnancies.

Fetal complications include neonatal hypoglycemia, hyperbilirubinemia, and shoulder dystocia. [Table 4] gives a brief list of both metabolic and nonmetabolic complications in the fetus and neonate of GDM.
Table 4: Fetal and neonatal complications in gestational diabetes mellitus in the peripartum period

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  Management Top

To avoid the maternal and fetal complications secondary to hyperglycemia during pregnancy, the management of GDM to maintain target blood glucose levels throughout pregnancy is of utmost importance. A program of medical nutritional therapy, self-monitoring of blood glucose levels (most of the newer glucometers have their readings calibrated to be plasma equivalents), and pharmacotherapy, when needed, improves perinatal outcomes such as reduction in preeclampsia, macrosomia, and shoulder dystocia. Moderate exercise also improves glycemic control and should be part of the treatment plan for patients with no medical or obstetric contraindications to this level of physical activity.[16]

  Counseling Top

Education of women with GDM about the implications (both short and long term) of the diagnosis, for her and her baby, and the beneficial impact of good blood glucose control throughout pregnancy are important. The treatment includes changes in diet and exercise and could involve medicines at the time of diagnosis of gestational diabetes. Replacing high glycemic index food with low glycemic index is emphasized. All women with GDM should be referred to a dietitian. Regular exercise, such as brisk walking for about 30 min, is recommended. Walking for 30 min after meals helps in reducing PP blood glucose.[11]

  Glucose Monitoring Top

Glucose levels are monitored several times daily in women with GDM. We suggest self-monitoring of blood glucose levels before breakfast and at 1 h after the beginning of each meal. The frequency of testing may be decreased to every other day in women with mild GDM and in whom no signs of fetal overgrowth (≥75th percentile of estimated fetal weight) and normal amniotic fluid volume are present.

  Medical Nutritional Therapy Top

Dietary management is the cornerstone of GDM care. Calories are generally divided over three meals and two to four snacks per day. Forty-five percent of the calories should be derived from carbohydrates, 20% from protein, and 35% from fat.[17] The diet should comprise adequate macronutrients and micronutrients. [Figure 1] shows the macronutrient and calorie distribution recommended as per medical nutrition therapy. The diet should also limit PP glucose excursions. The diet should prevent excessive maternal gestational weight gain. Calorie requirements are increased by 300 kcal/day in singleton pregnancies.[18] Twin pregnancies require higher weight gain targets.
Figure 1: Macronutrient distribution recommendation as per Medical Nutrition Therapy

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The calorie requirements as per pregestational body mass index (BMI) are 30 kcal/kg, 24 kcal/kg, and 14 kcal/kg for normal, overweight, and obese women, respectively.[19]

A moderate calorie restriction of about 33% or 1800 kcal/day may be advisable for obese women to control the blood glucose and excess weight gain while safely avoiding ketosis. To ensure sufficient fetal growth and cerebral development and function, the Institute of Medicine recommends a diet with ≥ 175 g of carbohydrates daily. Maternal ketonemia and/or ketonuria in pregnant women with diabetes have been associated with lower mental and/or motor function in the offspring. Hence, care should be taken to avoid starvation and ketosis. Bedtime snack is an important addition to avoid nocturnal and early morning hypoglycemia. Noncaloric sweeteners may be used in moderation.

  Physical Activity Top

Moderate-intensity exercise of 30 min, on most days, or brisk walking of about 150 min/week is recommended, if not contraindicated by an obstetrician. Activities such as walking, cycling, and swimming are important. They may reduce the onset of postpartum depression. Exercise may benefit fetal weight. Exercise could also limit postpartum weight gain. Diet and physical activity are sufficient to control the glycemic status in approximately 70%–85% of women with GDM.

  Pharmacotherapy Top

Pharmacotherapy is prescribed for women with GDM, who do not achieve adequate glycemic control with nutritional therapy and exercise alone. Pharmacotherapy can reduce the occurrence of macrosomia and large for gestational age in newborns.

Metformin and glyburide are the only oral antihyperglycemic drugs approved in pregnancy in the United States. Among the two, metformin is a better reasonable alternative for women with GDM who decline to take, or are unable to comply with, insulin therapy.[20],[21] Glyburide is not approved in India and many other countries outside the United States, and because of the risk of hypoglycemia, glyburide is best avoided. The long-term effects of transplacental passage of noninsulin antihyperglycemic agents are not known.

  Metformin – Metformin in Pregnancy trial Top

Metformin in Pregnancy (MiG) trial was an open, prospective, randomized, multicenter trial conducted in women with gestational diabetes, of age 18–45 years at 20–33 weeks of gestation. The results of the study showed that, in women with GDM, metformin (alone or with supplemental insulin) is not associated with increased perinatal complications as compared with insulin and that the women preferred metformin to insulin treatment.[22]

Metformin is recommended for GDM as per the National Institute for Health Care and Excellence guidelines. Metformin is a safe alternative for insulin, especially in women with mild gestational diabetes.[23] The dose of metformin can be started with 500 mg/day and titrated to a maximum of 2000 mg/day. However, it does cross the placenta. The Metformin in Gestational Diabetes: The offspring Follow-Up (MiG-TOFU) study showed that the total body fat of 2 year old offsprings of mothers who were randomly assigned to either metformin or insulin during pregnancy were similar. Further, at 7–9 years of age, the off-springs had similar total and abdominal fat in both groups. The metformin-exposed children were larger in weight, arm and waist circumferences, BMI, and lean mass at 9 years of age.[24]

The Society for Maternal-Fetal Medicine (SMFM) has recently published that in women with GDM in whom hyperglycemia is not controlled with medical nutritional therapy, metformin is a safe, first-line pharmacological alternative to insulin therapy (SMFM Publications Committee, 2018).[25]

  Insulin Top

Short-acting insulin analogs such as lispro and aspart seem to be safe in pregnancy and are given as prandial insulin to maintain 2-h PP below 120 mg/dl and long-acting insulin such as levemir and neutral protamine hagedorn (NPH), which also are safe in pregnancy are used as basal insulin to maintain fasting blood sugar below or equal to 95 mg/dl.[26],[27] In a systematic review and meta-analysis done in both pre-GDM and GDM women, the fetal safety of insulin glargine was compared with NPH and it was shown that there was no statistically significant difference in the fetal outcomes such as congenital anomalies, macrosomia, and neonatal hypoglycemia between the two insulin. Hence, insulin glargine can also be used as a safe alternative to NPH insulin. The starting dose of insulin can be calculated based on the weight alone (total daily dose of 0.7–1 u/kg given in divided doses), or based on both weight and trimester (0.7 u/kg in the first trimester, 0.8 u/kg in the second trimester, and 0.9–1 u/kg in the third trimester) and titrated further to maintain the target glycemic requirements. During intrapartum, intravenous (IV) insulin infusion along with hourly glucose monitoring is advised. If insulin requirement is less than 20 units, 24 h before labor, IV intrapartum insulin infusion may not be needed.[26] After delivery, insulin is stopped and capillary blood glucose is monitored for 24–48 h.

  Postpartum Testing Top

Patients with GDM should be screened for type 2 DM after pregnancy. Screening is performed at 4–12 weeks postpartum and, if negative, at least every 3 years thereafter. Lifestyle interventions (e.g., achieving a healthy weight, appropriate level of physical activity/exercise) are beneficial for reducing the incidence of type 2 diabetes and related comorbidities such as cardiovascular disease.[28]

  Case Vignette Top

Mrs. X, a 34-year-old female, primigravida who conceived after intrauterine insemination, was referred by her obstetrician for the management of GDM at 16 weeks of gestation. The OGTT showed that her fasting blood glucose was 102 mg/dl and 2 h after 75 g of oral glucose consumption was 154 mg/dl.

The other investigations, including thyroid tests, were normal. Family history is significant for diabetes in her father. No significant past medical/surgical history was noted. She was exercising about 15 min a day. Her medications included prenatal vitamins and aspirin 150 mg. She was asked to check the capillary blood glucose using glucometer about 6 times a day, and she continued to follow a healthy diet prescribed by a dietitian.

In spite of diet and exercise, since the self-monitored blood glucose (SMBG) values during her 17th week of gestation were above the target range as shown in [Table 5], she was started on pharmacotherapy with injection detemir 4 units at bedtime and tablet metformin 250 mg before dinner. Insulin dose was titrated, and after a month, at 20 weeks of gestation, follow-up showed fasting: 110 mg/dl, PP after breakfast within range.
Table 5: Self-monitored blood glucose of Mrs. X in the 17th week of gestation, with just diet and exercise

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Medications were further adjusted with gradual titration of injection detemir to 11 units at bedtime and tablet metformin 500 mg before dinner, and the SMBG improved further. However, owing to stress of an upper respiratory infection and other family issues, the fasting glucose again rose to 140 mg/dl at 24 weeks of gestation [Table 6].
Table 6: Self-monitored blood glucose of Mrs. X during her follow-up visits

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Further titration of medications with metformin 500 mg twice a day and insulin detemir 25 units at bedtime, and her glucose levels were better controlled with SMBG showing fasting: 106 mg/dl and PP: 121 mg/dl at 26 weeks of gestation. Finally, her SMBG was in the target range at 32 weeks of gestation as seen in [Table 6]. The blood glucose at different times of the day was also similar.

Mrs. X continued her SMBG and medications were titrated to maintain the target glucose levels.

  Summary Top

Tight control of blood glucose in GDM is important to prevent both maternal and fetal complications resulting from uncontrolled hyperglycemia. Mostly, GDM can be treated with lifestyle modification. Only about 30% of GDM requires pharmacotherapy with metformin, insulin, or both. With continuous self-monitoring of glucose and titration of medications to maintain the target blood glucose, both maternal and fetal complications secondary to hyperglycemia can be successfully avoided, thus ensuring a healthy mother and baby.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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