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Fetal blood sampling – how many samples are needed?
  1. L Santangeli,
  2. N Ratnavelu,
  3. WM Hair,
  4. AJ Thomson
  1. Royal Alexandra Hospital, Paisley, UK


Introduction Intrapartum fetal blood sampling (FBS) is a crucial tool in the assessment of fetal wellbeing. No published guidance or evidence exists regarding the number of samples required to support clinical decision-making; the authors sought to address this in the current study.

Methods FBS were obtained from 50 labouring women. Other data included number of samples obtained and analysed, sampling time, pH values and subsequent clinical decisions. An abnormal FBS value necessitating delivery or re-sampling was defined as <7.25.

Results 160 samples were obtained (median per patient=3, range 0–6), and 71% were processed successfully. 10/50 women had an FBS pH <7.25. In those patients whose first FBS pH was <7.20 (n=6), all subsequent samples were also abnormal. In patients whose first pH was 7.20–7.25 (n=4), subsequent pHs varied (range 7.20–7.29), but clinical decisions were based on the initial result. FBS sampling times ranged from 6 to 45 min.

Conclusion In those patients where FBS is indicated, there appears to be no benefit in obtaining more than one result. Indeed this may lead to unnecessary delays in clinical decision-making.

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