Clinical significance of umbilical cord artery blood gas analysis in labor

Objective To evaluate the clinical significance of umbilical cord artery blood gas analysis in labor.Methods Retrospective study of 810 pregnancy women delivered at Department of Obstetrics and Gynecology,Peking University First Hospital,between March,2005 and December,2006 was performed.There were 401 women who had fetal distress(distress group)and 409 women who had no fetal distress(non-distress group).Umbilical cord artery blood gas analysis was performed immediately after delivery and the outcome of neonates were follow-up.Results ① There were 49 cases(12.2%)whose pH value were less than 7.2 in distress group and 26 cases(6.4%)in non-distress group,the difference was significantly(P=0.004).The average value of pH in distress group(7.25±0.24)was significantly lower than that in non-distress group(7.28±0.05,P=0.023).② Among the neonates whose Apgar score7,the rate of umbilical artery pH value 7.2 was 8.3%,and among that whose Apgar score ≤7,the rate was 34.5%.There was a significant difference(P=0.000)between the two groups.③ There were 18 neonates with hypoxic ischemic encephalopathy(HIE).The sensitivity for Apgar score≤7 was 38.9%,specificity was 97.2%,the positive predictive value was 24.1%,negative predictive value was 98.6%.The sensitivity,specificity,positive predictive value and negative predictive value of pH7.2 for detect HIE were 55.6%,91.8%,13.3% and 98.9%,respectively.The specificity,positive predictive value and negative predictive value could be increased to 99.4%,50% and 98.4% after combining Apgar score and pH value.Conclusions There were over-diagnosis and over-treatment of fetal distress in clinical practice because only a few neonates had decreased pH value among fetal distress cases.The umbilical cord artery blood gas analysis is the supplement of Apgar score for fetal distress diagnosis.If we combine Apgar score and pH value of umbilical cord gas analysis,the specificity and positive predictive value for diagnosing HIE could be increased.