[CG] Umbilical Cord Sampling for pH at Delivery


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At delivery cord samples should be obtained from:

  • All babies with a suspicious or pathological CTG in labour
  • All babies who had FBS in labour (regardless of the result)
  • All babies with significant meconium in labour
  • All babies born with Apgar <5 at 1 minute and/or <7 at 5 minutes
  • All vaginal breech deliveries
  • All cases of shoulder dystocia
  • All cases with intrapartum fever >38°C
  • All babies with a birth weight < 10th centile
  • All preterm babies (24 – 36+6 weeks)


When taking a cord sample:


  1. Double clamp a section of the cord.
  2. Two heparinised syringes should be used to take the sample.
  3. Sample the umbilical vein and artery and identify each.

Importance of paired samples

  • Arterial blood better represents the condition of the fetus
  • A venous sample is less representative of the fetus
  • Single result gives no means of checking whether your sample was arterial or venous
  • A venous result may give additional information
  • A normal venous result does not rule out acidaemia
  • Normally expect a difference of at least 0.03 units between arterial and Venous pH readings
  1. Sampling should be completed as soon as possible after delivery but always within 30 minutes. If a delay is suspected store the clamped cord in the fridge.
  2. Should the analyser on labour ward be unavailable, there is another analyser available in the Neonatal Unit.
  3. Document as to whether there was delayed cord clamping and its duration.
  4. The result should be inserted onto Badger in the appropriate section (the Postnatal tab).
  5. The responsibility for obtaining the sample and documenting the result lies with the person delivering the woman.


Last reviewed: 04 December 2018

Next review: 01 December 2023

Author(s): Dr Marcus McMillan (Lead Author); Dr Lindsey MacDonald (Lead Author)