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Does low cord blood pH gasses determines fetal outcome?Dr. Ahmad Tayyib Azizan, Dr. H. Krishna Kumar

Tuanku Jaa’far Seremban Hospital, Negeri Sembilan Darul Khusus, Malaysia

Objectives

In 1958, James et al recognised that umbilical cord blood gas analysis can give an indication of preceding fetal hypoxic stress. It has since become widely accepted that umbilical cord blood gas analysis can provide important information about the past, present and possibly the future condition of the infant. Umbilical cord blood gas analysis is now recommended in all high‐risk deliveries by both the British and American Colleges of Obstetrics and Gynaecology, and in some centres particularly Tuanku Jaa’far Seremban Hospital (HTJS), Negeri Sembilan Darul Khusus, Malaysia it is practised routinely following all caesarian section deliveries, instrumental and high – risk deliveries. It is therefore of increasing clinical and medicolegal importance that substantial studies to show the correlation between low cord blood pH gasses and fetal outcome in the form of Apgar’s score.

It has been shown, however, that there is a poor correlation between Apgar scores and acid base status in the cord blood (cord blood pH) of neonates. The purpose of this study was to determine retrospectively the relation between Apgar scores, and cord blood gases.

Methods

This is a cross – sectional study which was done in a single tertiary obstetric center, Tuanku Jaa’far Seremban Hospital (HTJS), Negeri Sembilan Darul Khusus, Malaysia. A total of 492 consecutive deliveries at >35 weeks of gestation were selected for a period of time. Selected deliveries were only via Lower Segment Caesarian Sections including both elective and emergency caesarian sections regardless of the obstetric indications. However, this study excludes caesarian sections for premature deliveries <35 weeks. The gestational age was determined by the date of the mother's last normal menstrual period and early in utero ultrasound scan of the fetus. This study also exclude all vaginal birth deliveries.

At delivery the umbilical cord was double clamped within 30 seconds; heparinised blood was obtained from both the umbilical artery and vein, placed on ice, and taken for immediate blood gas analysis. Arterial and venousblood was collected separately into heparinised 1 mlpolyethylene syringes. Blood pH, Po2, and Pco2 were measured immediately after a blood sample was collected. Cord blood pH of less than 2.0 was taken as acidotic which may suggest fetal asphyxia and on the other hand, pH of more than 2.0 was taken as normal value.

The Apgar score was assigned by the senior medical officer from the paediatric department and senior midwife present at the delivery. The score was given at 1 and 5 minutes. Apgar’s score in the 1st minute would be considered good and normal if it is more than 5 and more than 7 at 5 th minutes. However, Apgar’s score in the 1st minute of less or equals to 5 and at 5th minutes of less or equals to 7 would be considered poor.

Student's t test was used when comparingmean values. The prevalence of pH<2.0 (acidotic) and fetal outcome as measured by baby’s Apgar’s score was calculated. The prevalence of pH>2.0 (normal) and fetal outcome as measured by babys’s Apgar’s score was calculated.

Results Conclusions

References

We were unable to substantiate the hypothesis that low cord blood pH gasses was related to poor fetal outcome in the form of Apgar’s score. Thus, cord blood pH gasses may not prognosticate and determines the baby’s outcome during intrapartum.

It is possible that the results we report do notreach significance because of the small numbers ofneonates in some of the gestational age groupsanalysed. This lack of statistical significance persisted however, when some of the groups were combined.

However, normal cord blood pH gasses may suggest good fetal outcome as shown in this study but further studies may need to be done to further evaluate these.

We report elsewhere that 98% of the cord blood pH gasses >2 gives good fetal outcome. We suggest that these babies less likely to suffer from birth asphyxia. This may also show that cord blood pH gasses have high specificity to determine good fetal outcome. However, we cannot elaborate further due to the limitations in this study.

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