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Stefan Johansson

Population-based reference curve for umbilical cord arterial pH in infants born at 28 to 42 weeks

8 posts in this topic

Dear all, I want to share one of my latest papers, in Journal of Perinatology. The publisher sent me a free full-text URL :) so if you click on http://rdcu.be/pLGB you can download the PDF.

So, with a large very detailed obstretric database we could investigate what is a normal umbilical artery pH in well preterm and term infants.

In the paper you also find a graphical representation what is a normal pH (a percentile chart, like a growth chart)

Our take-home-message is that fetal acidosis may not be well defined as a static cut.off (like <7.00 or <7.10) but rather like a gestational age-adjusted measurement, like <1st percentile.

Quote

 

Population-based reference curve for umbilical cord arterial pH in infants born at 28 to 42 weeks

OBJECTIVE: The objective of the study was to examine normal variations of umbilical cord arterial pH by gestational age (GA).

STUDY DESIGN: Population-based cohort study of 46 199 infants born from 2008 to 2014 in Stockholm, Sweden, with GA 28 to

42 weeks, Apgar score ⩾ 7 at 5 min, non-instrumental vaginal delivery, and birth weight for GA ⩾ 3rd and ⩽ 97th percentile.

Quantile regression was used to investigate the associations between GA and infant sex, and pH.

RESULTS: The mean umbilical cord arterial pH (s.d.) was 7.29 (0.10), 7.27 (0.07), 7.25 (0.07) and 7.23 (0.07) among infants born at 28

to 31, 32 to 36, 37 to 41 and 42 weeks, respectively. Arterial pH decreased linearly with increasing GA, and female infants had higher

pH than male infants (P<0.001).

CONCLUSION: Umbilical cord arterial pH varied in a linear fashion by GA and was influenced by infant sex. The provided reference

curve taking GA into account may yield a more accurate definition of acidosis at birth.

 

 

 

 

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Dear Dr. Johansson. Thanks for the great job and sharing it with us.

What do you think how elective C-section will influence the umbilical artery pH? What cut-off for cord blood acidosis do you use in practice -- 7.1 or 7.0? Sometimes we conflict with obstetricians about severity of acidosis, so in the light of this trial does it make sense to say that for example pH withing lower 5 to 10th percentile is a moderate acidosis? Many thanks. 

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@Andrej Vitushka Actually, we firsts included also elective CS in the "normal reference group" to get more statistical power in the analyses. However, the reviewers thought differentely :) and we skipped those. I don't have exact data in my head but elective CS had sign higher pH than normal vag delivery, but it was really on the 2nd decimal.

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Although we use no "definition" in our unit, I'd consider 7.00 as severe acidosis in a newborn. And 7.10 in an infant who is "crashing" in the unit due to sepsis, NEC etc.

For research purposes, our idea is to use something like <1st percentile as definiton of fetal acidosis

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Dear Stefan,

Wonderful study.

Did you also measure lactate levels?

Khalid

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Thanks a lot for the very valuable effort and every day practice problems.

I think how much is the bicarbonate and how much is the bicarbonate deficit will give a clue for the prognosis and outcome more than the pH .

What is ur opinion regarding this

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@Khaque we had no data on lactate, it is not routinely measured in umbilical cord blood.

@tarek although we did not formally investigate the components of pH, I'd say that PCO2 and BD would explain they differences over gestational age. We plan to dig further into the prognostic value of acidosis but the literature and My clinical experience too: I am not so convinced that acidosis alone is a good prognostic factor.

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