Understanding Gestational Diabetes

Understanding Gestational Diabetes


Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy and as a consequence of pregnancy, in contrast to pre-existing diabetes in pregnant women.1 During the late second trimester and early third trimester, insulin-mediated glucose uptake is greatly reduced. In healthy women, this insulin insensitivity is counteracted by a corresponding increase in insulin production to maintain blood sugar levels.2 GDM results when the body’s insulin secretion is insufficient to meet its needs.3 In many cases, women who develop GDM had asymptomatic insulin resistance and b-cell defects prior to conception.4,5 These defects only become clinically manifested as a result of pregnancy-induced insulin resistance.6 Usually, GDM is diagnosed during the late second trimester and resolves at giving birth.1



Every year, approximately 2% to 10% of every pregnancy in the U.S. is affected by GDM.7 In an analysis of 12.6 million first-time mothers in the U.S. between the ages of 15 to 44 who gave birth between 2011 to 2019, the rate of GDM increased from 47.6 to 63.5 per 1000 live births, amounting to an average annual increase of 3.7%.8 The increase was observed across all racial and ethnic groups. The study noted that the trend paralleled the rise in the prevalence of obesity, physical inactivity, and poor diet quality. Advanced maternal age, associated with an increased risk of GDM, may have contributed to the observed trend. However, only a modest increase (<2 years) in maternal age at delivery was observed over the past decade.9



There are several clinical, pregnancy-related, and lifestyle factors that are associated with an increased risk of developing GDM.6,10,11

Clinical Risk Factors

  • Overweight (body mass index (BMI) >25 kg/m2) or obesity (BMI >30 kg/m2)
  • Advanced maternal age
  • Family history of T2D
  • History of GDM or glucose intolerance
  • Polycystic ovary syndrome
  • Current glycosuria
  • Certain racial/ethnic background (Hispanic, Native American, South or East Asian, or Pacific Islander)
  • Other genetic factors


Pregnancy-Related Risk Factors

  • Previous infant with macrosomia (fetal overgrowth)
  • Male fetus
  • Number of previous pregnancies (>20 weeks of gestation)
  • Multiple pregnancy

Lifestyle Risk Factors

  • Poor dietary habits
  • Physical inactivity
  • Cigarette smoking


If left unmanaged, GDM can result in serious short-term and long-term health consequences for both the mother and the child.6

Short-Term Complications – GDM is associated with complications such as pre-eclampsia (high blood pressure and protein in urine), fetal overgrowth, operative delivery, birth canal lacerations, shoulder dystocia (baby’s shoulder(s) getting stuck during delivery), polyhydramnios (too much amniotic fluid), neonatal hypoglycemia (low blood sugar for the infant), jaundice, and even death of the fetus in rare cases.

Long-Term Complications – A meta-analysis of 20 cohort studies found that women with GDM are at a sevenfold increased risk of developing subsequent T2D when compared to women with normoglycemic pregnancies. They are also at a greater risk for developing metabolic syndrome, cardiovascular, retinal, liver, and kidney disease. Additionally, children of women with GDM are at an increased risk of developing insulin resistance, pre-diabetes, diabetes, metabolic syndrome, and being overweight.

Even though untreated GDM can have serious maternal and fetal consequences, GDM is generally easily managed through lifestyle changes, pharmacotherapy, and proper blood-glucose monitoring.

Lifestyle Management – Nearly 85% of patients with GDM can manage their illness and achieve target glucose levels through lifestyle changes (diet, physical activity, weight control) alone.12,13 The American Diabetes Association (ADA) recommends consulting a dietician to follow a personalized diet that provides adequate nutrition for the pregnancy yet restricts carbohydrate intake to 35% to 40% of daily calories.14,15 For those with obesity, the ADA suggests reducing daily caloric intake by 30% to 33%.15 Additionally, as long as there are no contraindications, they are encouraged to engage in pregnancy-safe physical activities throughout pregnancy. Weight loss is generally not recommended during pregnancy. Rather, appropriate and healthy weight gain should be encouraged. The Institute of Medicine recommends 25-35 lb weight gain for those with normal BMI (19.8-26.0 kg/m2) and 15-25 lb or <15 lb weight gain for those who are overweight or obese, respectively.16

Pharmacotherapy – Pharmacotherapy can be considered in patients whose glucose levels cannot adequately be controlled through lifestyle changes.15 It can also be considered when fetal overgrowth is noted on sonogram.20 Insulin therapy is the favored pharmacological agent, as it is both effective and safe for the fetus.15 Oral hypoglycemic agents are usually not recommended due to potential side effects, but metformin and glyburide may alternatively be used.21,22

Blood Glucose Monitoring – Alongside lifestyle and pharmacological management, patients with GDM should monitor their blood glucose levels through either intermittent self-monitoring or continuous glucose monitoring.17 For those who self-monitor, they are recommended to check their blood glucose levels before breakfast (ie, fasting glucose level) and at one or two hours after beginning each meal (ie, postprandial glucose level). The ADA gives the following recommendations as the upper limits for glucose levels:18,19

  • Fasting Blood Glucose Concentration: <95 mg/dL
  • One-Hour Postprandial Blood Glucose Concentration: <140 mg/dL
  • Two-Hour Postprandial Blood Glucose Concentration: <120 mg/dL


1. 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
2. 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
3. Buchanan TA, Xiang A, Kjos SL, Watanabe R. What Is Gestational Diabetes? Diabetes Care. 2007;30(Supplement_2):S105-S111. doi:10.2337/dc07-s201
4. Buchanan TA. Pancreatic B-Cell Defects in Gestational Diabetes: Implications for the Pathogenesis and Prevention of Type 2 Diabetes. J Clin Endocrinol Metab. 2001;86(3):989-993. doi:10.1210/jcem.86.3.7339
5. Catalano PM, Huston L, Amini SB, Kalhan SC. Longitudinal changes in glucose metabolism during pregnancy in obese women with normal glucose tolerance and gestational diabetes mellitus. Am J Obstet Gynecol. 1999;180(4):903-916. doi:10.1016/S0002-9378(99)70662-9
6. McIntyre HD, Catalano P, Zhang C, Desoye G, Mathiesen ER, Damm P. Gestational diabetes mellitus. Nat Rev Dis Primer. 2019;5(1):1-19. doi:10.1038/s41572-019-0098-8
7. CDC. Gestational Diabetes. Centers for Disease Control and Prevention. Published March 2, 2022. Accessed March 22, 2022. https://www.cdc.gov/diabetes/basics/gestational.html
8. 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. 2021;326(7):660-669. doi:10.1001/jama.2021.7217
9. Mathews TJ, Hamilton BE. Mean Age of Mothers is on the Rise: United States, 2000-2014. NCHS Data Brief. 2016;(232):1-8.
10. Serlin DC, Lash RW. Diagnosis and Management of Gestational Diabetes Mellitus. Am Fam Physician. 2009;80(1):57-62.
11. US Preventive Services Task Force. Screening for Gestational Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(6):531-538. doi:10.1001/jama.2021.11922
12. Landon MB, Spong CY, Thom E, et al. A multicenter, randomized trial of treatment for mild gestational diabetes. N Engl J Med. 2009;361(14):1339-1348. doi:10.1056/NEJMoa0902430
13. Crowther CA, Hiller JE, Moss JR, et al. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med. 2005;352(24):2477-2486. doi:10.1056/NEJMoa042973
14. American Diabetes Association. Gestational diabetes mellitus. Diabetes Care. 2003;26 Suppl 1:S103-105. doi:10.2337/diacare.26.2007.s103
15. Turok DK, Ratcliffe S, Baxley EG. Management of Gestational Diabetes Mellitus. Am Fam Physician. 2003;68(9):1767-1772.
16. Cheng YW, Chung JH, Kurbisch-Block I, Inturrisi M, Shafer S, Caughey AB. . Gestational Weight Gain and Gestational Diabetes Mellitus. Obstetrics & Gynecology. 2008; 112 (5): 1015-1022. doi: 10.1097/AOG.0b013e31818b5dd9.
17. Laird J, McFarland KF. Fasting blood glucose levels and initiation of insulin therapy in gestational diabetes. Endocr Pract Off J Am Coll Endocrinol Am Assoc Clin Endocrinol. 1996;2(5):330-332. doi:10.4158/EP.2.5.330
18. American Diabetes Association. 14. Management of Diabetes in Pregnancy: Standards of Medical Care in Diabetes-2021. Diabetes Care. 2021;44(Suppl 1):S200-S210. doi:10.2337/dc21-S014
19. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol. 2018;131(2):e49-e64. doi:10.1097/AOG.0000000000002501
20. Nicholson WK, Wilson LM, Witkop CT, et al. Therapeutic management, delivery, and postpartum risk assessment and screening in gestational diabetes. Evid ReportTechnology Assess. 2008;(162):1-96.
21. Kalra B, Gupta Y, Singla R, Kalra S. Use of Oral Anti-Diabetic Agents in Pregnancy: A Pragmatic Approach. North Am J Med Sci. 2015;7(1):6-12. doi:10.4103/1947-2714.150081
22. Bishop KC, Harris BS, Boyd BK, Reiff ES, Brown L, Kuller JA. Pharmacologic Treatment of Diabetes in Pregnancy. Obstet Gynecol Surv. 2019;74(5):289-297. doi:10.1097/OGX.0000000000000671



The content of this article is intended to provide a general information and knowledge on the subject matter. The views expressed in newsletters, articles, and blogs in the i-SENS USA website are not necessarily those of i-SENS Incorporated, i-SENS USA Incorporated or our publishers. Medical or nutritional information on i-SENS USA website is not intended to replace professional medical advice – you should always consult a specialist with any questions about your specific circumstances.

Add a comment