Diabetes Review OSCE - Gestational Diabetes

Diagnosis: Gestational Diabetes

Case Overview

  • Age/Sex: 33-year-old female
  • Occupation: Primary school teacher
  • Setting: Antenatal clinic / GP clinic referral for a diabetes check-up
  • Chief complaint: "My midwife said my sugar was a bit high — I'm here for a diabetes check-up."

Patient Script

Who I Am

I'm 33, I work as a primary school teacher and I'm about 26 weeks pregnant with my second baby.

What Brings Me In

My midwife said my routine pregnancy sugar test was high last week, so she asked me to come for a diabetes check-up.

My Story

I had my routine antenatal appointment one week ago and they did the usual screening where I had to drink that sweet drink; they told me the nurse was concerned because my number was a bit high and asked me to see someone. Over the last three weeks I've been a bit more thirsty than usual and getting up at night to pee once or twice more than before, but I figured that was just pregnancy. I also noticed my vision gets a little bit blurry sometimes in the evening, but it clears up. I have no nausea or vomiting now, and the baby feels fine when I notice kicks occasionally. My first pregnancy went fine but my first baby was quite big — they said he was about 4.1 kg at birth and I had a long labour.

I haven't been on any special diet since I got pregnant; I try to eat reasonably but I do have a sweet tooth — I sometimes have a couple of biscuits in the afternoon. I work long days and have been a bit more tired than usual for the last month. I had a urinary infection during my first trimester and took antibiotics for a few days, but that cleared up and I haven't had any burning now.

My Medical Background

  • Past medical history: previous pregnancy (G1) delivered at term; baby was 4.1 kg (macrosomia)
  • Pre-pregnancy weight: BMI around 31 (overweight/obese)
  • Medications: folic acid and routine pregnancy multivitamin; I take no regular medications
  • Allergies: none known
  • Social: non-smoker, stopped alcohol when pregnant; lives with partner; works full-time as a teacher
  • Family history: mother has type 2 diabetes; no one else with significant illness

What I Think & Worry About

  • I think maybe I'm developing diabetes again in this pregnancy because my first baby was big.
  • I'm worried I might harm the baby if my sugars are high, and I don’t want another difficult delivery or for the baby to be unwell after birth.
  • I’m a bit anxious about needles and being told I might need insulin.

If You Ask Me About Other Symptoms...

  • Headaches: I get occasional headaches from time to time, which I put down to tiredness.
  • Vision: I sometimes have mild blurring in the evenings, then it clears.
  • Thirst/urination: Thirsty more than usual over the last 3 weeks and getting up once or twice more at night.
  • Weight: I’m gaining weight as expected in pregnancy; I haven’t tried to lose weight.
  • Infections: I had a urinary tract infection in the first trimester that was treated; no current burning or fever.
  • Medications/Herbs: I don’t take herbal remedies or extra supplements beyond the pregnancy vitamins.

Clinical Summary

Examination

  • General: alert, comfortable, not in acute distress
  • Vitals: BP 118/76 mmHg, HR 82 bpm, RR 16/min, Temperature 36.8°C
  • Weight/BMI: pre-pregnancy BMI ~31; current pregnancy weight increased appropriately
  • Abdominal: fundal height consistent with 26 weeks gestation
  • Obstetric: fetal heart rate 145 bpm, reactive
  • Peripheral: no oedema beyond mild ankle puffiness; no acanthosis nigricans noted

Investigations

  • Random capillary glucose (clinic): 10.0 mmol/L (180 mg/dL) (elevated)
  • 50 g glucose challenge test (1-hour): 11.2 mmol/L (202 mg/dL) (positive screen)
  • 75 g oral glucose tolerance test (performed subsequently): fasting 5.6 mmol/L (101 mg/dL), 1-hour 11.8 mmol/L (212 mg/dL), 2-hour 9.6 mmol/L (173 mg/dL) (meets WHO diagnostic thresholds for gestational diabetes)
  • HbA1c: 5.9% (41 mmol/mol) (consistent with hyperglycaemia in pregnancy but not diagnostic of long-standing diabetes)
  • Urinalysis: glucosuria ++, nitrites negative, leukocyte esterase negative
  • Renal function and electrolytes: creatinine 60 µmol/L, electrolytes within normal limits (suitable for pregnancy)

Diagnosis

  • Primary diagnosis: Gestational diabetes mellitus (GDM)

    • Evidence: positive 50 g screening test followed by diagnostic 75 g OGTT with fasting 5.6 mmol/L, 1-hour 11.8 mmol/L, 2-hour 9.6 mmol/L, at approximately 26 weeks gestation; risk factors include maternal age >30, BMI ~31, previous macrosomic infant, family history of T2DM.

  • Differential diagnoses and reasoning:

    • Pre-existing (overt) type 2 diabetes: less likely because HbA1c only mildly elevated and normal pre-pregnancy history of symptoms; would be more likely if very high fasting glucose or HbA1c at first antenatal visit.
    • Transient hyperglycaemia due to infection or medications: unlikely — no current infection and no steroids or other hyperglycaemic drugs reported.
    • Glycosuria from high pregnancy GFR alone: possible contributor, but biochemical OGTT confirms systemic hyperglycaemia.

Management

  • Immediate:

    • Explain diagnosis and implications to patient, addressing her concerns about the baby and needles.
    • Refer to diabetes-in-pregnancy clinic / obstetric team for shared care and education.
    • Arrange dietitian review for individualized medical nutrition therapy and structured carbohydrate advice.
    • Teach self-monitoring of blood glucose (SMBG): fasting and 1-hour postprandial checks initially; targets: fasting ≤5.3 mmol/L (95 mg/dL), 1-hour postprandial ≤7.8 mmol/L (140 mg/dL) (or use local targets if different).

  • Pharmacological escalation if lifestyle measures fail or glucose markedly elevated:

    • If persistent hyperglycaemia despite diet/exercise (usually trial 1–2 weeks), consider metformin as first-line oral agent in many settings or start insulin if very high glucose, symptomatic, or patient preference/contraindication to metformin.
    • Provide instruction/support for insulin if required (start dose and regimen guided by diabetes team).

  • Obstetric care and fetal monitoring:

    • Arrange growth ultrasound around 28–32 weeks (and repeat as clinically indicated) to monitor for accelerated fetal growth.
    • Increase antenatal surveillance for fetal wellbeing as per local protocols.

  • Safety and baseline tests:

    • Check baseline LFTs and renal function if starting metformin/insulin.
    • Provide education on recognising symptoms of hypo-/hyperglycaemia and when to seek urgent care.

  • Postpartum follow-up:

    • Plan 75 g OGTT at 6–12 weeks postpartum to detect persistent dysglycaemia.
    • Advise on long-term risk of type 2 diabetes and lifestyle measures; arrange primary-care follow-up for annual screening.

Key Learning Points

  • Screen for gestational diabetes typically between 24–28 weeks gestation; use a 50 g glucose challenge screening followed by diagnostic OGTT per local guidelines.
  • Diagnosis is based on measured glucose thresholds (WHO/ADA thresholds differ slightly); management begins with diet and SMBG, escalating to pharmacologic therapy (metformin or insulin) if targets are not met.
  • GDM increases risks of fetal macrosomia, birth complications and neonatal hypoglycaemia; postpartum screening is essential because of the higher lifetime risk of type 2 diabetes.

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