A woman with pre-gestational Type 1 diabetes at 30 weeks presents with vomiting and deep sighing respiration. Arterial pH is 7.15, bicarbonate 8 mmol/L, ketonuria positive, and plasma glucose 210 mg/dL. Which statement best explains her presentation?
- A This picture is inconsistent with ketoacidosis because glucose exceeds 250 mg/dL is required for the diagnosis
- B Ketoacidosis in pregnancy develops at substantially lower glucose levels than in the non-pregnant state ✓
- C The acidosis is lactic rather than ketoacidotic because of the relatively low glucose
- D Pregnancy buffers ketosis, so acidosis this severe implies urosepsis
Correct answer: B. Ketoacidosis in pregnancy develops at substantially lower glucose levels than in the non-pregnant state
Explanation
Because of enhanced renal glucose clearance, placental transfer of glucose to the fetus, and the buffering effect of the fetoplacental unit, ketoacidosis in pregnant women can develop with plasma glucose as low as 150 to 200 mg/dL. Waiting for a glucose above 250 mg/dL risks missing the diagnosis, and maternal ketonaemia carries a significant fetal loss risk, so treatment must start immediately regardless of the glucose value.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.