Seminars in Fetal & Neonatal Medicine xxx (2015) 1e8
Contents lists available at ScienceDirect
Seminars in Fetal & Neonatal Medicine journal homepage: www.elsevier.com/locate/siny
Review
Clinical relevance of fetal hemodynamic monitoring: Perinatal implications Jay D. Pruetz a, b, *, Jodie Votava-Smith a, David A. Miller b a b
Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA Department of Obstetrics & Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
s u m m a r y Keywords: Fetal monitoring Antepartum testing Prenatal diagnosis Neonatal critical care Perinatal management Doppler velocimetry
Comprehensive assessment of fetal wellbeing involves monitoring of fetal growth, placental function, central venous pressure, and cardiac function. Ultrasound evaluation of the fetus using 2D, color Doppler, and pulse-wave Doppler techniques form the foundation of antenatal diagnosis of structural anomalies, rhythm abnormalities and altered fetal circulation. Accurate and timely prenatal identification of the fetus at risk is critical for appropriate parental counseling, antenatal diagnostic testing, consideration for fetal intervention, perinatal planning, and coordination of postnatal care delivery. Fetal hemodynamic monitoring and serial assessment are vital to ensuring fetal wellbeing, particularly in the setting of complex congenital anomalies. A complete hemodynamic evaluation of the fetus gives important information on the likelihood of a smooth postnatal transition and contributes to ensuring the best possible outcome for the neonate. © 2015 Published by Elsevier Ltd.
1. Introduction The fetal circulation involves oxygenation within the placenta and two functional ventricles pumping in parallel along with three shunts: the ductus venosus, foramen ovale, and ductus arteriosus. Major disturbances of organ development involving the heart and lungs can be well tolerated by the fetus as long as the placental circulation and shunts remain intact with at least one patent inflow and outflow tract, and one ventricle capable of supporting combined cardiac output (CO). However, certain extracardiac malformations (ECMs), severe forms of congenital heart disease (CHD), and acquired conditions have the potential to disrupt maternal, placental, or fetal circulation, thus posing a threat to fetal wellbeing. Ultrasound evaluation of the fetus using 2D, color Doppler, and pulse-wave Doppler techniques form the foundation of antenatal diagnosis of structural anomalies, rhythm abnormalities, and altered fetal circulation. Comprehensive assessment of fetal wellbeing involves monitoring of fetal growth, placental function, central venous pressure, and cardiac function. Accurate and timely
* Corresponding author. Address: Keck School of Medicine, University of Southern California, Division of Pediatric Cardiology, Children's Hospital Los Angeles, 4650 Sunset Blvd, Mailstop #34, Los Angeles, CA 90027, USA. Tel.: þ1 323 361 4657; fax: þ1 323 361 1513. E-mail address: [email protected] (J.D. Pruetz).
prenatal identification of the fetus at risk is critical for appropriate parental counseling, antenatal diagnostic testing, assessment for fetal intervention, perinatal planning, and co-ordination of postnatal care delivery. This article reviews the essential tools and techniques used for hemodynamic monitoring of the fetus and their clinical importance from the obstetricians', perinatologists', neonatologists', and pediatric sub-specialists' perspective. 2. Methods of fetal evaluation 2.1. Fetal biometry Consistent fetal growth that is appropriate for gestational age (GA) is one of the most important markers of fetal wellbeing. Sonographic evaluation of fetal growth incorporates standard measurements of the fetal head, abdomen, and femur, that can be used to estimate fetal weight by formulas such as those by Shepard or Hadlock [1,2]. Abnormalities of fetal growth can be caused by placental dysfunction, primary growth failure of the fetus (i.e. genetic anomaly) or secondary to a disease state in the fetus. For example, chronic placental dysfunction is characterized by a recognizable pattern of asymmetric fetal growth. Fetal blood containing oxygen and nutrients is shunted preferentially to the vital organs of the brain, heart and adrenal glands at the expense of the limbs, kidneys, intestine and liver. The resulting limitation of
http://dx.doi.org/10.1016/j.siny.2015.03.007 1744-165X/© 2015 Published by Elsevier Ltd.
Please cite this article in press as: Pruetz JD, et al., Clinical relevance of fetal hemodynamic monitoring: Perinatal implications, Seminars in Fetal & Neonatal Medicine (2015), http://dx.doi.org/10.1016/j.siny.2015.03.007
2
J.D. Pruetz et al. / Seminars in Fetal & Neonatal Medicine xxx (2015) 1e8
hepatic growth and glycogen storage contributes to an asymmetrically smaller abdominal circumference relative to the fetal head measurements. Growth of the long bones may also be affected. Reduced renal perfusion and urine production may result in reduction of amniotic fluid volume. Fetal growth restriction usually is classified as an estimated fetal weight below the 10th or 5th percentile for GA. For the purposes of obstetric management, Doppler velocimetry usually is reserved for the setting of fetal growth restriction, in which it is used as an adjunct to traditional methods of antepartum fetal surveillance, including fetal heart rate (FHR) monitoring, ultrasound evaluation of fetal biophysical variables, and amniotic fluid volume assessment.
reported a corrected fetal loss rate of 3.2/1000 and FNR of 1.9/1000 [4]. Corresponding rates with the CST were 0.4/1000 and 0/1000. Manning reported an average FNR of 6.4/1000 among nine large clinical trials using the NST as the primary method of surveillance [10]. Assessment of FHR characteristics other than reactivity (baseline rate, variability, decelerations) may improve the sensitivity of the test. Decelerations may be observed in 33e50% patients undergoing weekly NSTs and reactive tests accompanied by variable decelerations were associated with rates of meconium passage and cesarean for fetal indications similar to those encountered with non-reactive tests [11e13].
2.2. Fetal heart rate monitoring
2.5. Biophysical profile
Normal central nervous system (CNS) regulation of the FHR is an essential marker of fetal wellbeing. Normal baseline rate, normal FHR variability, and heart rate accelerations are highly predictive of normal fetal oxygenation. On the other hand, FHR decelerations usually reflect a transient decrease or interruption of fetal oxygenation, often secondary to uterine contractions or intermittent compression of the umbilical cord. Antepartum testing is reserved for pregnancies at increased risk for interruption of fetal oxygenation. Common indications include maternal hypertension, post-term pregnancy, and suspected or confirmed fetal growth restriction. The goals of antepartum testing are (i) to identify interruption of fetal oxygenation so that permanent injury or death might be prevented and (ii) to identify normally oxygenated fetuses so that unnecessary intervention can be avoided. The effectiveness of an antepartum test is measured by the false-negative rate (FNR) and false-positive rate (FPR). The FNR is defined as the incidence of fetal death within one week of a normal antepartum test. The FPR is defined as the incidence of abnormal tests that prompts delivery, but that are not associated with evidence of acute or chronic suboptimal fetal oxygenation.
The biophysical profile (BPP), as described by Manning et al., assesses five biophysical variables [14]. Fetal movement, breathing, tone, and NST reflect acute CNS function, whereas amniotic fluid volume serves as a marker of the longer-term adequacy of placental function. Two points are assigned for each normal variable and zero points for each abnormal variable, for a maximum score of 10. A BPP score of 8e10, with normal amniotic fluid volume, is considered normal. A score of 6 is equivocal and usually warrants repeat testing the following day. Scores 5 cm but 1.5 multiples of the median (MoM) for gestational age identify fetuses at increased risk for anemia who may be candidates for cordocentesis and intrauterine transfusion [26]. In growth-restricted fetuses with abnormal UA velocimetry, there is some evidence that elevated MCA PSV can improve prediction of adverse outcome [27]. Resistance in the MCA normally decreases with advancing GA. Diastolic velocities are characteristically low, but may rise due to redistribution of brain blood flow in the setting of suboptimal fetal oxygenation. The “brain-sparing” effect of fetal hypoxemia likely results from a combination of sympathetic reflex-centralization of circulating blood volume, and altered cerebral autoregulation in the setting of lowered fetal blood oxygen content [28]. If decreased fetal oxygenation is attributable to increased resistance to fetal perfusion of the placenta, resistance indices in the umbilical artery will increase, whereas resistance indices in the MCA will move in the opposite direction. These phenomena led to the description of the cerebroplacental ratio (CPR), a calculation that uses the MCA PI as the numerator and the umbilical artery PI as the denominator. By expressing opposite-direction resistance changes as a ratio, the CPR magnifies them, making them more apparent. Among 123 women referred for evaluation of fetal growth restriction, Bahado-Singh et al. identified 87 with normal CPR findings and 36 with CPR
Please cite this article in press as: Pruetz JD, et al., Clinical relevance of fetal hemodynamic monitoring: Perinatal implications, Seminars in Fetal & Neonatal Medicine (2015), http://dx.doi.org/10.1016/j.siny.2015.03.007
4
J.D. Pruetz et al. / Seminars in Fetal & Neonatal Medicine xxx (2015) 1e8
Contents lists available at ScienceDirect
Seminars in Fetal & Neonatal Medicine journal homepage: www.elsevier.com/locate/siny
Review
Clinical relevance of fetal hemodynamic monitoring: Perinatal implications Jay D. Pruetz a, b, *, Jodie Votava-Smith a, David A. Miller b a b
Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA Department of Obstetrics & Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
s u m m a r y Keywords: Fetal monitoring Antepartum testing Prenatal diagnosis Neonatal critical care Perinatal management Doppler velocimetry
Comprehensive assessment of fetal wellbeing involves monitoring of fetal growth, placental function, central venous pressure, and cardiac function. Ultrasound evaluation of the fetus using 2D, color Doppler, and pulse-wave Doppler techniques form the foundation of antenatal diagnosis of structural anomalies, rhythm abnormalities and altered fetal circulation. Accurate and timely prenatal identification of the fetus at risk is critical for appropriate parental counseling, antenatal diagnostic testing, consideration for fetal intervention, perinatal planning, and coordination of postnatal care delivery. Fetal hemodynamic monitoring and serial assessment are vital to ensuring fetal wellbeing, particularly in the setting of complex congenital anomalies. A complete hemodynamic evaluation of the fetus gives important information on the likelihood of a smooth postnatal transition and contributes to ensuring the best possible outcome for the neonate. © 2015 Published by Elsevier Ltd.
1. Introduction The fetal circulation involves oxygenation within the placenta and two functional ventricles pumping in parallel along with three shunts: the ductus venosus, foramen ovale, and ductus arteriosus. Major disturbances of organ development involving the heart and lungs can be well tolerated by the fetus as long as the placental circulation and shunts remain intact with at least one patent inflow and outflow tract, and one ventricle capable of supporting combined cardiac output (CO). However, certain extracardiac malformations (ECMs), severe forms of congenital heart disease (CHD), and acquired conditions have the potential to disrupt maternal, placental, or fetal circulation, thus posing a threat to fetal wellbeing. Ultrasound evaluation of the fetus using 2D, color Doppler, and pulse-wave Doppler techniques form the foundation of antenatal diagnosis of structural anomalies, rhythm abnormalities, and altered fetal circulation. Comprehensive assessment of fetal wellbeing involves monitoring of fetal growth, placental function, central venous pressure, and cardiac function. Accurate and timely
* Corresponding author. Address: Keck School of Medicine, University of Southern California, Division of Pediatric Cardiology, Children's Hospital Los Angeles, 4650 Sunset Blvd, Mailstop #34, Los Angeles, CA 90027, USA. Tel.: þ1 323 361 4657; fax: þ1 323 361 1513. E-mail address: [email protected] (J.D. Pruetz).
prenatal identification of the fetus at risk is critical for appropriate parental counseling, antenatal diagnostic testing, assessment for fetal intervention, perinatal planning, and co-ordination of postnatal care delivery. This article reviews the essential tools and techniques used for hemodynamic monitoring of the fetus and their clinical importance from the obstetricians', perinatologists', neonatologists', and pediatric sub-specialists' perspective. 2. Methods of fetal evaluation 2.1. Fetal biometry Consistent fetal growth that is appropriate for gestational age (GA) is one of the most important markers of fetal wellbeing. Sonographic evaluation of fetal growth incorporates standard measurements of the fetal head, abdomen, and femur, that can be used to estimate fetal weight by formulas such as those by Shepard or Hadlock [1,2]. Abnormalities of fetal growth can be caused by placental dysfunction, primary growth failure of the fetus (i.e. genetic anomaly) or secondary to a disease state in the fetus. For example, chronic placental dysfunction is characterized by a recognizable pattern of asymmetric fetal growth. Fetal blood containing oxygen and nutrients is shunted preferentially to the vital organs of the brain, heart and adrenal glands at the expense of the limbs, kidneys, intestine and liver. The resulting limitation of
http://dx.doi.org/10.1016/j.siny.2015.03.007 1744-165X/© 2015 Published by Elsevier Ltd.
Please cite this article in press as: Pruetz JD, et al., Clinical relevance of fetal hemodynamic monitoring: Perinatal implications, Seminars in Fetal & Neonatal Medicine (2015), http://dx.doi.org/10.1016/j.siny.2015.03.007
2
J.D. Pruetz et al. / Seminars in Fetal & Neonatal Medicine xxx (2015) 1e8
hepatic growth and glycogen storage contributes to an asymmetrically smaller abdominal circumference relative to the fetal head measurements. Growth of the long bones may also be affected. Reduced renal perfusion and urine production may result in reduction of amniotic fluid volume. Fetal growth restriction usually is classified as an estimated fetal weight below the 10th or 5th percentile for GA. For the purposes of obstetric management, Doppler velocimetry usually is reserved for the setting of fetal growth restriction, in which it is used as an adjunct to traditional methods of antepartum fetal surveillance, including fetal heart rate (FHR) monitoring, ultrasound evaluation of fetal biophysical variables, and amniotic fluid volume assessment.
reported a corrected fetal loss rate of 3.2/1000 and FNR of 1.9/1000 [4]. Corresponding rates with the CST were 0.4/1000 and 0/1000. Manning reported an average FNR of 6.4/1000 among nine large clinical trials using the NST as the primary method of surveillance [10]. Assessment of FHR characteristics other than reactivity (baseline rate, variability, decelerations) may improve the sensitivity of the test. Decelerations may be observed in 33e50% patients undergoing weekly NSTs and reactive tests accompanied by variable decelerations were associated with rates of meconium passage and cesarean for fetal indications similar to those encountered with non-reactive tests [11e13].
2.2. Fetal heart rate monitoring
2.5. Biophysical profile
Normal central nervous system (CNS) regulation of the FHR is an essential marker of fetal wellbeing. Normal baseline rate, normal FHR variability, and heart rate accelerations are highly predictive of normal fetal oxygenation. On the other hand, FHR decelerations usually reflect a transient decrease or interruption of fetal oxygenation, often secondary to uterine contractions or intermittent compression of the umbilical cord. Antepartum testing is reserved for pregnancies at increased risk for interruption of fetal oxygenation. Common indications include maternal hypertension, post-term pregnancy, and suspected or confirmed fetal growth restriction. The goals of antepartum testing are (i) to identify interruption of fetal oxygenation so that permanent injury or death might be prevented and (ii) to identify normally oxygenated fetuses so that unnecessary intervention can be avoided. The effectiveness of an antepartum test is measured by the false-negative rate (FNR) and false-positive rate (FPR). The FNR is defined as the incidence of fetal death within one week of a normal antepartum test. The FPR is defined as the incidence of abnormal tests that prompts delivery, but that are not associated with evidence of acute or chronic suboptimal fetal oxygenation.
The biophysical profile (BPP), as described by Manning et al., assesses five biophysical variables [14]. Fetal movement, breathing, tone, and NST reflect acute CNS function, whereas amniotic fluid volume serves as a marker of the longer-term adequacy of placental function. Two points are assigned for each normal variable and zero points for each abnormal variable, for a maximum score of 10. A BPP score of 8e10, with normal amniotic fluid volume, is considered normal. A score of 6 is equivocal and usually warrants repeat testing the following day. Scores 5 cm but 1.5 multiples of the median (MoM) for gestational age identify fetuses at increased risk for anemia who may be candidates for cordocentesis and intrauterine transfusion [26]. In growth-restricted fetuses with abnormal UA velocimetry, there is some evidence that elevated MCA PSV can improve prediction of adverse outcome [27]. Resistance in the MCA normally decreases with advancing GA. Diastolic velocities are characteristically low, but may rise due to redistribution of brain blood flow in the setting of suboptimal fetal oxygenation. The “brain-sparing” effect of fetal hypoxemia likely results from a combination of sympathetic reflex-centralization of circulating blood volume, and altered cerebral autoregulation in the setting of lowered fetal blood oxygen content [28]. If decreased fetal oxygenation is attributable to increased resistance to fetal perfusion of the placenta, resistance indices in the umbilical artery will increase, whereas resistance indices in the MCA will move in the opposite direction. These phenomena led to the description of the cerebroplacental ratio (CPR), a calculation that uses the MCA PI as the numerator and the umbilical artery PI as the denominator. By expressing opposite-direction resistance changes as a ratio, the CPR magnifies them, making them more apparent. Among 123 women referred for evaluation of fetal growth restriction, Bahado-Singh et al. identified 87 with normal CPR findings and 36 with CPR
Please cite this article in press as: Pruetz JD, et al., Clinical relevance of fetal hemodynamic monitoring: Perinatal implications, Seminars in Fetal & Neonatal Medicine (2015), http://dx.doi.org/10.1016/j.siny.2015.03.007
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J.D. Pruetz et al. / Seminars in Fetal & Neonatal Medicine xxx (2015) 1e8
