[Fetal blood analysis--pro and contra]

Fetal blood gas analysis (FBA) or micro blood gas analysis (MBU) is seen worldwide as an integral part of modern obstetrics. However, there are a number of obstetricians who practise obstetrics quite safely and competently without MBU. The aim of this study was to find out what effect MBU frequency (%) had on vital obstetric performance parameters.

This study was based on the obstetric parameters of 1,003 clinics in Ostwestfalen-Lippe in the years 1990-1996. The percentages of 10 principal variables (including cesarean section, forceps, acidosis rates, postpartal mortality) were calculated per clinic/year. Correlations (according to Kendall) were established between the individual variables to estimate the influence of MBU frequency (%) on the different variables. Data from the 1,003 clinics in the years 1990-1996 could be pooled.

Approximately 91% of all clinics perform FBA. The mean MBU frequency is 6.1 +/- 10.1%, the median is 2.3%. Upward variance is large: the 90th percentile of MBU distribution amounts to 15.5, the 95th centile to 22.6%. There is no correlation between MBU frequency (%) and clinic size, measured by the number of children born per year. There is no statistically relevant connection between the acidosis rate (%) in umbilical artery (UA) blood and MBU frequency. The same holds true for mortality (%) of neonates in the first week. However, there is a highly significant positive correlation between MBU frequency on the one hand and cesarean and forceps rates (%) on the other. Clinics without FBA (n = 88, approximately 9%) have obstetric performance figures that are as good as those of the total amount of clinics examined. There is no correlation between the acidosis rate (pH < 7.100, UA (%)) and neonatal mortality in the first week. However, a significant correlation between pH values < 7.000 (UA) and an increased postnatal mortality (p < 0.001) has been observed.

In analogy to cardiotocography, cesarean and forceps rates are increased in FBA, although there is no statistically significant decrease in acidosis morbidity and postpartal mortality. These figures support the observation that obstetrics without FBA is possible and legitimate. The significance of FBA for fetal diagnosis lies in the small number of cases where cardiotocograms are hard to interpret. Therefore, every obstetrician should be able to handle it. A new evaluation of pH values is discussed.