A C TA Obstetricia et Gynecologica
AOGS RE V I EW AR TIC LE
Fetal scalp blood sampling in labor – a review JAN S. JØRGENSEN1 & TOM WEBER2 1
Department of Gynecology and Obstetrics, Odense University Hospital, University of Southern Denmark, Institute of Clinical Research, Perinatal Research Unit, Odense, and 2Department of Gynecology and Obstetrics, Hvidovre Hospital, University of Copenhagen, Hvidovre, Denmark
Key words Fetal scalp blood sampling, fetal monitoring, labor, neonatal outcome, cardiotocography Correspondence Jan S. Jørgensen, Department of Gynecology and Obstetrics, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense C, Denmark. E-mail: [email protected] Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article; however, both authors hold a strong conviction that FBS is a beneficial supplement to CTG. Please cite this article as: Jørgensen JS, Weber T. Fetal scalp blood sampling in labor – a review. Acta Obstet Gynecol Scand 2014; 93:548–555.
Abstract During the 1970s and 1980s, electronic fetal monitoring and fetal scalp blood sampling were introduced without robust evidence. With a methodical review of the published literature, and using one randomized controlled trial, seven controlled studies, nine randomized studies of various surveillance methods and data from the Danish National Birth Registry, we have assessed the usefulness of fetal scalp blood sampling as a complementary tool to improve the specificity and sensitivity of electronic cardiotocography. Based on heterogeneous studies of modest quality with somewhat inconsistent results, we conclude that fetal scalp blood sampling in conjunction with cardiotocography can reduce the risk of operative delivery. Fetal scalp blood sampling can provide additional information on fetal wellbeing and fetal reserves at a time before decisions are made concerning the need for and timing of operative delivery and the choice of anesthesia, and be an adjunct in the interpretation of cardiotocography patterns. CI, confidence interval; CS, cesarean section; CTG, cardiotocography; FBS, fetal scalp blood sampling; RCT, randomized controlled trial.
Abbreviations:
Received: 17 December 2013 Accepted: 5 May 2014 DOI: 10.1111/aogs.12421
Introduction Following the initial development of electronic fetal motoring by Hon and Petrie (1), during the 1970s and 1980s this surveillance modality was rapidly introduced into obstetric practice, spreading to most high- and middle-income countries. The introduction was made on the assumption that electronic fetal motoring would help to reduce cerebral palsy (CP) caused by intrapartum asphyxia (2). What actually happened was that the incidence of severe intrapartum asphyxia was only slightly reduced and CP rates among infants born at term remained unchanged. What changed dramatically was the cesarean section (CS) rate, which rose four- to fivefold between 1970 and 1990 (3). One reason for this was that whereas a normal cardiotocography (CTG) tracing is a
548
strong indicator of the absence of intrapartum asphyxia, the interpretation of CTGs carries significant inter- and intra-observer variation and a non-reassuring or abnormal CTG may not be associated with acidosis and subsequent asphyxia. False positives from high sensitivity but
Key Message As a supplement to cardiotocography, fetal blood sampling can:
• •
Reduce the rate of operative delivery. Provide more accurate information on the fetal status and reserves before decisions on operative delivery and choice of anesthesia are made.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 548–555
J.S. Jørgensen & T. Weber
low specificity may result in unnecessary interventions such as operative vaginal delivery and emergency CS (4). A supplementary test was needed to increase the specificity of CTG and to reduce the number of unnecessary interventions. Fetal scalp blood sampling (FBS) to measure scalp pH and lactate was introduced as a tool to improve the performance of electronic fetal motoring. This review summarizes the development and evaluates the effect and usefulness of FBS as a supplement to CTG.
History of biochemical fetal monitoring during labor In Berlin in 1962, Erich Saling first reported the use of FBS during labor. He described how with an amnioscope, a light source and a knife (originally a razor blade), he could collect by mouth suction, drops of fetal scalp blood into a heparinized tube. These were then transferred to an acidbase laboratory for rapid analysis and reporting of the fetal acid-base balance (5). Almost 20 years later, he reported on the number of fetal deaths over a 30-year period among 50 000 deliveries during the change in fetal monitoring from auscultation alone (1955–60) to auscultation in combination with FBS (1961–67) to CTG and FBS (1968–79). Intrapartum deaths fell in these three time periods from 0.8 to 0.32%, and then to 0.15%. He credited FBS as the main reason for this decline (6). FBS was introduced as an additional clinical test in many obstetric units during the 1970s and 1980s and remains in daily use (7). Normally, pH is measured in the fetal scalp blood. Usually 15–50 lL is required ( three to four drops of blood) for measurement in an acid-base machine/laboratory. A pH value >7.25 is regarded as normal, demonstrating fetal wellbeing and normal oxygenation. Values between 7.25 and 7.20 are regarded as sub-normal and require extra vigilance and repeat sampling within 20– 30 min. Values of pH < 7.20 (or
AOGS RE V I EW AR TIC LE
Fetal scalp blood sampling in labor – a review JAN S. JØRGENSEN1 & TOM WEBER2 1
Department of Gynecology and Obstetrics, Odense University Hospital, University of Southern Denmark, Institute of Clinical Research, Perinatal Research Unit, Odense, and 2Department of Gynecology and Obstetrics, Hvidovre Hospital, University of Copenhagen, Hvidovre, Denmark
Key words Fetal scalp blood sampling, fetal monitoring, labor, neonatal outcome, cardiotocography Correspondence Jan S. Jørgensen, Department of Gynecology and Obstetrics, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense C, Denmark. E-mail: [email protected] Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article; however, both authors hold a strong conviction that FBS is a beneficial supplement to CTG. Please cite this article as: Jørgensen JS, Weber T. Fetal scalp blood sampling in labor – a review. Acta Obstet Gynecol Scand 2014; 93:548–555.
Abstract During the 1970s and 1980s, electronic fetal monitoring and fetal scalp blood sampling were introduced without robust evidence. With a methodical review of the published literature, and using one randomized controlled trial, seven controlled studies, nine randomized studies of various surveillance methods and data from the Danish National Birth Registry, we have assessed the usefulness of fetal scalp blood sampling as a complementary tool to improve the specificity and sensitivity of electronic cardiotocography. Based on heterogeneous studies of modest quality with somewhat inconsistent results, we conclude that fetal scalp blood sampling in conjunction with cardiotocography can reduce the risk of operative delivery. Fetal scalp blood sampling can provide additional information on fetal wellbeing and fetal reserves at a time before decisions are made concerning the need for and timing of operative delivery and the choice of anesthesia, and be an adjunct in the interpretation of cardiotocography patterns. CI, confidence interval; CS, cesarean section; CTG, cardiotocography; FBS, fetal scalp blood sampling; RCT, randomized controlled trial.
Abbreviations:
Received: 17 December 2013 Accepted: 5 May 2014 DOI: 10.1111/aogs.12421
Introduction Following the initial development of electronic fetal motoring by Hon and Petrie (1), during the 1970s and 1980s this surveillance modality was rapidly introduced into obstetric practice, spreading to most high- and middle-income countries. The introduction was made on the assumption that electronic fetal motoring would help to reduce cerebral palsy (CP) caused by intrapartum asphyxia (2). What actually happened was that the incidence of severe intrapartum asphyxia was only slightly reduced and CP rates among infants born at term remained unchanged. What changed dramatically was the cesarean section (CS) rate, which rose four- to fivefold between 1970 and 1990 (3). One reason for this was that whereas a normal cardiotocography (CTG) tracing is a
548
strong indicator of the absence of intrapartum asphyxia, the interpretation of CTGs carries significant inter- and intra-observer variation and a non-reassuring or abnormal CTG may not be associated with acidosis and subsequent asphyxia. False positives from high sensitivity but
Key Message As a supplement to cardiotocography, fetal blood sampling can:
• •
Reduce the rate of operative delivery. Provide more accurate information on the fetal status and reserves before decisions on operative delivery and choice of anesthesia are made.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 548–555
J.S. Jørgensen & T. Weber
low specificity may result in unnecessary interventions such as operative vaginal delivery and emergency CS (4). A supplementary test was needed to increase the specificity of CTG and to reduce the number of unnecessary interventions. Fetal scalp blood sampling (FBS) to measure scalp pH and lactate was introduced as a tool to improve the performance of electronic fetal motoring. This review summarizes the development and evaluates the effect and usefulness of FBS as a supplement to CTG.
History of biochemical fetal monitoring during labor In Berlin in 1962, Erich Saling first reported the use of FBS during labor. He described how with an amnioscope, a light source and a knife (originally a razor blade), he could collect by mouth suction, drops of fetal scalp blood into a heparinized tube. These were then transferred to an acidbase laboratory for rapid analysis and reporting of the fetal acid-base balance (5). Almost 20 years later, he reported on the number of fetal deaths over a 30-year period among 50 000 deliveries during the change in fetal monitoring from auscultation alone (1955–60) to auscultation in combination with FBS (1961–67) to CTG and FBS (1968–79). Intrapartum deaths fell in these three time periods from 0.8 to 0.32%, and then to 0.15%. He credited FBS as the main reason for this decline (6). FBS was introduced as an additional clinical test in many obstetric units during the 1970s and 1980s and remains in daily use (7). Normally, pH is measured in the fetal scalp blood. Usually 15–50 lL is required ( three to four drops of blood) for measurement in an acid-base machine/laboratory. A pH value >7.25 is regarded as normal, demonstrating fetal wellbeing and normal oxygenation. Values between 7.25 and 7.20 are regarded as sub-normal and require extra vigilance and repeat sampling within 20– 30 min. Values of pH < 7.20 (or
