Fact Explanation
Diagnosis during screening Gestational diabetes (GDM) is defined as carbohydrate intolerance of varying severity with the onset or first recognition during the current pregnancy.[1] The prevalence of GDM in the United States is estimated to be 7% and further increasing.[2] Pregnant women with gestational diabetes are usually asymptomatic. Blood glucose screening during the antenatal period identifies a majority of patients. Pregnancy is a diabetogenic state. The maternal carbohydrate metabolism is adjusted to increase fetal supply of glucose. Hormones produced during pregnancy – estrogen, progesterone, prolactin, Human placental lactogen (hPL) have anti-insulin properties. The insulin action is resisted. Body lipids and proteins are mobilized. Free fatty acids and amino-acids are used for maternal energy needs while maintaining an adequate supply of glucose to the fetus.
Presentation with maternal complications Infections are common during pregnancy due to impaired immunity. Curd like thick white vaginal discharge associated with vulval discomfort, pruritus is due to vaginal Candidiasis. Urinary tract infections are common infections in diabetic patients. Lower urinary tract infections may present with dysuria, frequency, suprapubic discomfort and fever. Some patients may be asymptomatic (Asymptomatic bacteriuria). High fever associated with chills and rigors with loin pain, urinary symptoms, nausea and vomiting may suggest pyelonephritis. Pre-eclampsia is frequently associated with diabetic women. These patients may present with headache, visual blurring, vomiting etc. Severe pre-eclampsia may progress to generalized tonic-clonic seizures - Eclampsia.[3]
Polyuria, polydipsia and nocturia These features can be present in women with severe hyperglycaemia.
Identified during physical examination of the mother Pregnant women with gestational diabetes have an increased risk of macrosomia and polyhydramnios. Increased symphysio-fundal height and increased estimated fetal weight may be detected during abdominal examination.
Abdominal discomfort, breathlessness, increased abdominal girth These features are due to polyhydramnios. There is excess amniotic fluid accumulation due to increased fetal urine production.
Past obstetric history A past history of macrosomic infants may suggest undiagnosed gestational diabetes. In addition a past history of prolonged labor, obstructed labor, shoulder dystocia, fetal injuries, neonatal respiratory distress etc may be present.
  1. HOLLANDER MH, PAARLBERG KM, HUISJES AJ. Gestational diabetes: a review of the current literature and guidelines. Obstet Gynecol Surv [online] 2007 Feb, 62(2):125-36 [viewed 11 August 2014] Available from: doi:10.1097/01.ogx.0000253303.92229.59
  2. HILLIER TA, VESCO KK, PEDULA KL, BEIL TL, WHITLOCK EP, PETTITT DJ. Screening for gestational diabetes mellitus: a systematic review for the U.S. Preventive Services Task Force. Ann Intern Med [online] 2008 May 20, 148(10):766-75 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18490689
  3. Hyperglycemia and Adverse Pregnancy Outcomes. N Engl J Med [online] 2008 May, 358(19):1991-2002 [viewed 11 August 2014] Available from: doi:10.1056/NEJMoa0707943


Fact Explanation
Physical examination of the mother Usually normal.
Obstetric abdominal examination : Increased estimated fetal weight Maternal hyperglycaemia leads to increased glucose supply to the fetus. Increased glucose, amino-acid supply to the fetus stimulates growth. In addition the resulting fetal hyperinsulinemia further promotes fetal growth due to the growth factor like action of insulin.
Obstetric abdominal examination : Features of polyhydramnios Polyhydramnios is a complication of diabetic pregnancies. The fetal hyperglycaemia promotes osmotic dieresis and increased urine production by the fetal kidneys. This results in excess amniotic fluid.[1] The abdomen appears tense. The symphysio-fundal height is increased and the fetal parts are difficult to palpate.
  1. NOBILE DE SANTIS MS, RADAELLI T, TARICCO E, BERTINI S, CETIN I. Excess of amniotic fluid: pathophysiology, correlated diseases and clinical management. Acta Biomed [online] 2004:53-5 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/15301291

Differential Diagnoses

Fact Explanation
Pre-gestational diabetes The incidence of diabetic pregnancies has increased because more pregnancies now occur in women of advanced age. The patient may be a known diabetic. Gestational diabetes diagnosed early in the pregnancy may actually be pre-gestational diabetes. The clinical history and physical examination findings are similar to gestational diabetes. In addition to the complications associated with gestational diabetes, these patients have a higher risk of fetal anomalies and first trimester miscarriage. Poor glycaemic control during the period of organogenesis results in cardiac, neural tube and renal anomalies. Caudal regression syndrome although rare is a characteristic anomaly associated with pre-gestational diabetes.[1] Blood glucose control in the mother is relatively more difficult with an increased risk of ketosis. These patients may also have pre-existing vasculopathy. IUGR may result due to poor blood flow to the fetus. These patients require more intensive monitoring and management of blood glucose level. Insulin is usually required for blood glucose control.
  1. RAY J.G.. Preconception care and the risk of congenital anomalies in the offspring of women with diabetes mellitus: a meta-analysis. [online] 2001 August, 94(8):435-444 [viewed 09 August 2014] Available from: doi:10.1093/qjmed/94.8.435

Investigations - for Diagnosis

Fact Explanation
Oral glucose tolerance test (OGTT) Both the 75g two hour OGTT and the 100g three hour OGTT are used to confirm the diagnosis. The patient is advised to consume an unrestricted diet including > 150g of carbohydrate per day for 3 days prior to the test. The test is started after an overnight fast of at least 8 hours where the patient is given the amount of glucose to consume over about 20 minutes. The patient should refrain from smoking during the test. Blood glucose measurements are taken at the beginning, at 1h,2h and 3h periods. The cut off values used vary from country to country due to differences in the prevalence of GDM. Cut off values used by the American Diabetic Association : fasting > 95 mg/dl, 1-hour > 180 mg/dl, 2-hour > 155 mg/dl and 3-hour > 140 mg/dl.[1] Two or more abnormal values are required for diagnosis.[2] In addition the HAPO guidelines and the WHO guidelines are also used for diagnosis. The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study cut-off for diagnosis of GDM are fasting 92 mg/dL, 1-hour 180 mg/dL, or 2 hours 153 mg/dL.[3]
Random blood glucose assessment High risk patients with clear symptoms of hyperglycaemia can be diagnosed by a random blood glucose assessment. The cutoff value used is > 200 mg/dl.
Fasting blood sugar Fasting blood sugar assessment is rarely used as a diagnostic test.
  1. Standards of Medical Care in Diabetes--2013. Diabetes Care [online] December, 36(Supplement_1):S11-S66 [viewed 11 August 2014] Available from: doi:10.2337/dc13-S011
  2. PERKINS J. M., DUNN J. P., JAGASIA S. M.. Perspectives in Gestational Diabetes Mellitus: A Review of Screening, Diagnosis, and Treatment. Clinical Diabetes [online] 2007 April, 25(2):57-62 [viewed 11 August 2014] Available from: doi:10.2337/diaclin.25.2.57
  3. COUSTAN DR, LOWE LP, METZGER BE, DYER AR, INTERNATIONAL ASSOCIATION OF DIABETES AND PREGNANCY STUDY GROUPS. The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study: paving the way for new diagnostic criteria for gestational diabetes mellitus. Am J Obstet Gynecol [online] 2010 Jun, 202(6):654.e1-6 [viewed 11 August 2014] Available from: doi:10.1016/j.ajog.2010.04.006

Investigations - Followup

Fact Explanation
Blood glucose measurements Blood glucose levels need to be regularly monitored. Target blood sugar levels : fasting blood sugar < 108mg/dl and postprandial blood sugar < 126mg/dl. Blood sugar series assesses the blood glucose levels before and after the main meals – breakfast, lunch and dinner. Home glucose monitoring improves patient participation and hence promotes better control.
HbA1c HbA1c can be used assess the blood glucose control over the last 2-3 month period.
Ultrasound scan First trimester fetal ultrasound scan for accurate estimation of the gestational age is important since majority of pregnancies are induced at 38 weeks. Fetal anomaly scan is done at 22-24 weeks. During the third trimester ultrasound scan is important to monitor for fetal macrosomia and other complications. Further evaluation is required on the use of ultrasound scan parameters to guide management of gestational diabetes.[1]
Urine for microscopy and culture To exclude asymptomatic bacteriuria and overt urinary tract infection.[2]
  1. BALSELLS M, GARCíA-PATTERSON A, GICH I, CORCOY R. Ultrasound-guided compared to conventional treatment in gestational diabetes leads to improved birthweight but more insulin treatment: systematic review and meta-analysis. Acta Obstet Gynecol Scand [online] 2014 Feb, 93(2):144-51 [viewed 11 August 2014] Available from: doi:10.1111/aogs.12291
  2. RENKO M, TAPANAINEN P, TOSSAVAINEN P, POKKA T, UHARI M. Meta-Analysis of the Significance of Asymptomatic Bacteriuria in Diabetes Diabetes Care [online] 2011 Jan, 34(1):230-235 [viewed 11 August 2014] Available from: doi:10.2337/dc10-0421

Investigations - Screening/Staging

Fact Explanation
Screening for gestational diabetes This has being a much debated topic with divided opinion regarding universal screening and selective screening. In selective screening patients are categorized into low, average and high risk categories of acquiring GDM. The risk factors considered include : age > 25 years, pre-pregnancy obesity (BMI > 25 kg/m2), first-degree relative with diabetes, high risk ethnicity, previous history of macrosomia and polycystic ovarian syndrome.[1] Ethnic origin has a strong association with gestational diabetes. Apart from Caucasians other ethnicities such as South East Asian, Black etc are associated with a high prevalence of GDM.[2] Selective screening carries the risk of under-diagnosis while being a cost-effective method. Countries have resorted to use the appropriate screening method depending on the prevalence of diabetes.[3] A two step process is usually used for diagnosis – screening test followed by OGTT. In high risk patients the clinician can directly proceed to the diagnostic OGTT.
Screening for glycouria with urinalysis This method has a low sensitivity and specificity in identifying patients with GDM. The normal physiological changes associated with pregnancy may result in increased glucose excretion.
Oral glucose challenge test A one hour 50g-OGCT can also be used as a screening test. Fasting is not required.
Fasting blood glucose assessment Use of fasting blood glucose test as a screening test carries a sensitivity and specificity of 70-90% and 50-75% respectively at a threshold value of 4.8 mmol/l.[4] An additional diagnostic test is often required to confirm the diagnosis. Even though fasting blood glucose assessment is an easy screening procedure to perform it is not recommended for routine use.
HbA1c HbA1c is not recommended as a screening test for GDM.[5]
  1. DI CIANNI G, VOLPE L, LENCIONI C, MICCOLI R, CUCCURU I, GHIO A, CHATZIANAGNOSTOU K, BOTTONE P, TETI G, DEL PRATO S, BENZI L. Prevalence and risk factors for gestational diabetes assessed by universal screening. Diabetes Res Clin Pract [online] 2003 Nov, 62(2):131-7 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/14581150
  2. ORNHORST A, PATERSON CM, NICHOLLS JS, WADSWORTH J, CHIU DC, ELKELES RS, JOHNSTON DG, BEARD RW. High prevalence of gestational diabetes in women from ethnic minority groups. Diabet Med [online] 1992 Nov, 9(9):820-5 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/1473322
  3. ARORA D, ARORA R, SANGTHONG S, LEELAPORN W, SANGRATANATHONGCHAI J. Universal screening of gestational diabetes mellitus: prevalence and diagnostic value of clinical risk factors. J Med Assoc Thai [online] 2013 Mar, 96(3):266-71 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/23539927
  4. PERUCCHINI D, FISCHER U, SPINAS GA, HUCH R, HUCH A, LEHMANN R. Using fasting plasma glucose concentrations to screen for gestational diabetes mellitus: prospective population based study. BMJ [online] 1999 Sep 25, 319(7213):812-5 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/10496823
  5. AGARWAL MM, DHATT GS, PUNNOSE J, KOSTER G. Gestational diabetes: a reappraisal of HBA1c as a screening test. Acta Obstet Gynecol Scand [online] 2005 Dec, 84(12):1159-63 [viewed 11 August 2014] Available from: doi:10.1111/j.0001-6349.2005.00650.x

Management - General Measures

Fact Explanation
Patient education The patient should be provided information regarding the natural history of the disease, aetiology, investigations and treatment options. Counsel the patient regarding the complications to the mother and the fetus. It is important to motivate the patient to get involved in the management process.
Multi-disciplinary management Ideally these women should be managed in specific diabetic clinics. Physician, dietician, neonatologist should be involved in the management in addition to the obstetrician and midwife staff.
Dietary therapy Dietary control is a cornerstone in glycaemic control. Proper glycaemic control has been shown to reduce perinatal complications.[1] All diabetic pregnant women require diet control. Patients with gestational diabetes are initially started on dietary therapy. Review blood sugar control after two to three weeks. If adequate control is maintained dietary therapy alone may be adequate. Patients should be encouraged to have a calorie intake of 24-30kcal/kg body weight. Food items with a low glycaemic index are more suitable. The diet should contain adequate protein and fiber. Avoid sweet products and high fat food items. The calorie intake should be divided among 3 main meals and 3 snacks. A night snack can prevent nocturnal hypoglycaemia.
Adequate exercise Encourage suitable moderate intensity exercises. Upper body exercises are safe and effective. Regular exercise has been shown to reduce diabetes related maternal and fetal complications.[2]
Frequent clinic visits These patients require more frequent antenatal monitoring. Patients are usually monitored 2 weekly up to 32-34 weeks gestation and weekly there onwards. Blood glucose level, blood pressure, weight gain, proteinuria and fetal growth should be monitored at these visits.
  1. CROWTHER CA, HILLER JE, MOSS JR, MCPHEE AJ, JEFFRIES WS, ROBINSON JS, AUSTRALIAN CARBOHYDRATE INTOLERANCE STUDY IN PREGNANT WOMEN (ACHOIS) TRIAL GROUP. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med [online] 2005 Jun 16, 352(24):2477-86 [viewed 11 August 2014] Available from: doi:10.1056/NEJMoa042973
  2. BARAKAT R, PELAEZ M, LOPEZ C, LUCIA A, RUIZ JR. Exercise during pregnancy and gestational diabetes-related adverse effects: a randomised controlled trial. Br J Sports Med [online] 2013 Jul, 47(10):630-6 [viewed 11 August 2014] Available from: doi:10.1136/bjsports-2012-091788

Management - Specific Treatments

Fact Explanation
Insulin therapy Insulin therapy is required if the blood glucose cannot be controlled by dietary therapy alone. A mixture of short acting and medium acting insulin is preferred. The total dose is divided into 2/3 in the morning and 1/3 in the evening. Insulin is administered 20-30 minutes prior to the meal. The regimes used differ depending on the preference of the clinician.
Oral hypoglycaemic drugs Generally avoided due to the risk of fetal hypoglycaemia after passing through the placenta. Newer evidence suggests the possibility of using metformin during pregnancy.[2]
Time of delivery Patients with gestational diabetes are usually induced at 38 weeks gestation. This is due to the risk of sudden intrauterine death. Induction of labor at 38-39 weeks has shown to reduce the incidence of shoulder dystocia.[3] Both mechanical and medical methods of induction of labor can be used.
Mode of delivery Diabetes alone is not an indication for caesarian section. Caesarean section is requires more often due to macrosomia and other complications.
Management during labor Labor needs close supervision. It is important to maintain euglycaemia during labor. The morning insulin dose is skipped and an insulin+dextrose infusion is started. Blood glucose levels are monitored frequently and adjustments are made according to a sliding scale. Provide adequate pain relief to the mother by epidural anesthesia. Maintain the partogram. Monitor fetal heart rate continuously. An experienced obstetrician and pediatrician should be present at the time of delivery if fetal complications of macrosomia such as shoulder dystocia, obstructed labor, birth asphyxia, birth injuries are expected.
Neonatal care Neonates require intensive monitoring during the early postpartum period. Common complications during this period are hypoglycaemia, hypothermia, metabolic changes, respiratory distress syndrome and hyperbilirubinemia. Neonatal hypoglycaemia is an important complication. The blood glucose level should be monitored frequently. Encourage early breast feeding.[4]
Postpartum care Insulin can be stopped after the delivery. Monitor the blood glucose levels within the first 48h. The women should be educated about the increased risk of type 2 diabetes in future. They should be encouraged to continue the dietary changes and exercise adopted during the pregnancy. Counseling should be provided on the risk of gestational diabetes in subsequent pregnancies. Encourage pre-pregnancy planning for future pregnancies.
Contraception Barrier methods, low dose pills and depot preparations of progesterone are preferred.
  1. Diagnosis and Treatment of Gestational Diabetes (Scientific Impact Paper 23). Royal College of Obstetricians and Gynaecologists, 2011 [Viewed on 2014 August 09]. Available from : http://www.rcog.org.uk/womens-health/clinical-guidance/diagnosis-and-treatment-gestational-diabetes-sac-opinion-paper-23
  2. DHULKOTIA JS, OLA B, FRASER R, FARRELL T. Oral hypoglycemic agents vs insulin in management of gestational diabetes: a systematic review and metaanalysis. Am J Obstet Gynecol [online] 2010 Nov, 203(5):457.e1-9 [viewed 11 August 2014] Available from: doi:10.1016/j.ajog.2010.06.044
  3. LURIE S, INSLER V, HAGAY ZJ. Induction of labor at 38 to 39 weeks of gestation reduces the incidence of shoulder dystocia in gestational diabetic patients class A2. Am J Perinatol [online] 1996 Jul, 13(5):293-6 [viewed 11 August 2014] Available from: doi:10.1055/s-2007-994344
  4. PERSSON B, HANSON U. Neonatal morbidities in gestational diabetes mellitus. Diabetes Care [online] 1998 Aug:B79-84 [viewed 11 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/9704232