Labour: umbilical cord blood gases: practice question

A OBG question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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OBG · Labour: umbilical cord blood gases

Sample item

A term neonate is born flat after a prolonged deceleration. Umbilical arterial cord blood shows pH 6.95 and a base deficit of 14 mmol/L. How is this interpreted?

ASignificant metabolic acidosis, consistent with acute intrapartum hypoxiaBAn artefact from venous samplingCPure respiratory acidosis from cord compression onlyDNormal values for a term neonate

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Significant metabolic acidosis, consistent with acute intrapartum hypoxia

Cord arterial pH below 7.00 with a base deficit of 12 mmol/L or more is evidence of significant metabolic acidosis and one of the criteria for an acute intrapartum hypoxic event. Normal arterial pH is about 7.2 to 7.3, and venous values are higher. These values help to document asphyxia and to guide neonatal management such as therapeutic hypothermia.

Option by option

A. Significant metabolic acidosis, consistent with acute intrapartum hypoxia (correct)
Correct. pH under 7.0 with base deficit of 12 or more indicates metabolic acidosis from hypoxia.
B. An artefact from venous sampling
The pattern fits true arterial acidosis; mixed samples would not show such a low pH.
C. Pure respiratory acidosis from cord compression only
A large base deficit signals a metabolic component, not a pure respiratory problem.
D. Normal values for a term neonate
These values are far from the normal range.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this OBG question

What is the answer to this OBG question?

The best answer is A, Significant metabolic acidosis, consistent with acute intrapartum hypoxia. Cord arterial pH below 7.

Why is "An artefact from venous sampling" not the answer?

The pattern fits true arterial acidosis; mixed samples would not show such a low pH.

Why is "Pure respiratory acidosis from cord compression only" not the answer?

A large base deficit signals a metabolic component, not a pure respiratory problem.

Why is "Normal values for a term neonate" not the answer?

These values are far from the normal range.

What concept does this question test?

It tests Labour: umbilical cord blood gases in OBG. 00 with a base deficit of 12 mmol/L or more is evidence of significant metabolic acidosis and one of the criteria for an acute intrapartum hypoxic event. Normal arterial pH is about 7.2 to 7.3, and venous values are higher. These values help to document asphyxia and to guide neonatal management such as therapeutic hypothermia.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Labour: umbilical cord blood gases?

Learn management algorithms as steps: PPH, eclampsia, ectopic pregnancy. Then use the flashcards and the other OBG questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.