INTRAPARTUM ASSESSMENT OF FETAL WELL-BEING - A COMPARISON OF SCALP STIMULATION WITH SCALP BLOOD-PH SAMPLING

Objective: To determine whether the need for fetal scalp pH sampling i s decreased by the scalp stimulation test and whether redefinition of reactivity and presence of variability further decrease the need for s calp pH sampling. Methods: One hundred eight women with fetal heart ra te (FHR) patterns suggestive of acidosis underwent fetal scalp blood p H evaluations. Digital scalp stimulation was performed for 15 seconds 1-2 minutes before pH sampling. The study group was subdivided based o n reactivity to scalp stimulation and scalp puncture and was correlate d with pH values. Reactivity was defined as an acceleration of 15 beat s per minute or more lasting at least 15 seconds and redefined as an a cceleration of 10 beats per minute or more lasting at least 10 seconds . Nonreactive responses were subdivided based on FHR variability prece ding the scalp stimulation and were correlated with pH values. Fisher exact test was used for analysis. Results: All 51 instances of acceler ation of 15 beats per minute or more lasting at least 15 seconds follo wing scalp stimulation had a scalp pH of 7.20 or more. Using an accele ration of 10 beats per minute or more lasting at least 10 seconds, sev en more reactive responses were obtained after scalp stimulation, all with pH of 7.20 or more. The 15 instances in which the pH was less tha n 7.20 were nonreactive irrespective of the definition of reactivity ( P < .001). Twenty-one of the 50 instances of nonreactive responses (re active response: acceleration of 10 beats per minute or more lasting a t least 10 seconds) had positive variability. Only two of these 21 (9. 5%) instances compared to 13 of the 29 (45%) instances with negative v ariability had pH less than 7.20 (P < .007).Conclusions: The scalp sti mulation test could decrease the need for fetal scalp blood sampling b y 47%. Redefinition of reactivity could decrease the need for scalp sa mpling by 54%. In addition, assessment of FHR variability before scalp stimulation could decrease further the need for scalp blood sampling by 73%. Copyright (C) 1997 by The American College of Obstetricians an d Gynecologists.