AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1 January 1991
FETAL AND UTEROPLACENTAL FLOW VELOCITY WAVEFORMS AND PLACENTAL GRADING S. Degani, M.D., Y. Paltieli, M.D., R. Lewinsky, M.D., D. Abramovici, M.D., and M. Sharf, M.D.
ABSTRACT
Various sonographic placental changes such as patterns of calcification and echo-free spaces were correlated with advancing gestational age.1-3 In 1979, Grannum and associates4 reported the first systematic placental sonographic classification. These investigators studied the placental chorionic plate, placental substance, and basal plate in an attempt to correlate variation in sonographic appearance to fetal maturity as judged by amniotic pulmonary maturity index. Using the Grannum classification, Petrucha and Platt5 found a positive correlation between placental grade and gestational age. Anatomic and histologic correlative studies documented echogenic appearance of the placenta and subchorionic sonolucent areas representing reticular calcification1 fibrin deposition, hematoma, and cystic degeneration.3 However, the functional significance of these sonographic findings is still to be elucidated. The object of this study was to relate Doppler flow velocity waveforms in fetal, umbilical, and placental vessels to different placental grades. PATIENTS AND METHODS
A combined mechanical sector and pulsed Doppler system (Diasonics DRF 400) with a carrier frequency of 3.5 MHz was used for blood flow velocity
Downloaded by: NYU. Copyrighted material.
Doppler studies were performed on umbilical, fetal internal carotid, and arcuate arteries within 36 to 40 weeks of gestation in 85 women (66 with healthy pregnancies and 18 complicated by growth retardation), and results were analyzed by calculating the pulsatility index. In each case the placenta was examined and graded sonographically. No significant correlation was found between pulsatility index in fetal and uteroplacental vessels and placental grading in normal pregnancies. This suggests that tissue changes responsible for the echogenicity of maturing placenta are not directly related to vascular impedance of the placental vascular bed.
recordings in the internal carotid artery, umbilical artery, and arcuate arteries in 66 normal pregnancies (group I) and 18 cases of intrauterine growth retardation (IUGR; group II). All measurements were performed within 36 to 40 weeks of pregnancy. Gestational age varied between 36 and 40 weeks. The methodology used was first described by McCallum et al6 for the umbilical artery. Wladimiroff et al7 for the internal carotid artery, and Campbell et al8 for the arcuate arteries. The degree of pulsatility was quantified by calculating the pulsatility index.9 It was selected as the optimal method of analysis since results can be obtained even when the end-diastolic ratio becomes infinity or negative. The placenta was graded by the Grannum classification4 according to the most advanced portion of the placenta. The pulsatility index results were not known to the sonologist examining the grade of placenta. Group II consisted of 18 women with pregnancies complicated by severe IUGR of varying causes. All birthweights were below the 10th percentile for gestational age according to Brenner's tables, corrected for maternal parity and fetal sex.10 These charts applied to our population. Differences in pulsatility index between groups were tested using paired t test.
Ultrasound Unit, Department of Obstetrics & Gynecology, Haifa City Medical Center (Rothschild), Haifa, Israel Reprint requests: Dr. Degani, Department of Obstetrics & Gynecology, Ultrasound Unit, Haifa City Medical Center (Rothschild), P.O.B. 4940, Haifa 31048, Israel Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
47
graphic and pathologic studies (Spirt et al2) correlated calcification with advancing gestational age, which were more common in higher parity. Grannum et al4 and others13 showed fetal lung maturity with absence of respiratory distress syndrome in patients who had grade III placentas. Subsequent studies, however, have not confirmed the correlation, using Grannum's classification.14'15 Placental maturation as detected sonographically appears to be accelerated in association with IUGR,1617 consistent with the proposed concept of premature placental senescence. Giles et al18 and McCowan et al19 have demonstrated reduced mean small arterial vessel count in placentas from pregnancies with abnormal flow velocity waveform of the umbilical artery. They proposed that an increase in placental bed resistance caused by obliteration of these vessels is the primary cause of the change observed in the flow velocity waveforms of the umbilical artery. Their results show a small increase in arterial vessel count per microscope field during normal pregnancy, but the reduced flow resistance is primarily due to increase in placental size. These histologic changes are not detected by the current methods of placental grading. In our study absence of significant difference inflowvelocity waveforms between the various placental grades and normal flow patterns in grade III placentas in pregnancies not complicated by severe intrauterine growth retardation, suggest that there is no correlation between the sonographic findings and the functional changes in blood flow. Grade III placentas are more common in postdates; however (in agreement with our findings), umbilical artery velocimetry is not very useful in the
RESULTS
Clinical features of group I (66 normal pregnancies) included: mean maternal age, 26.6 ± 6 years; parity, 1.4 ± 1.1; gestational age at delivery, 39 weeks ± 3 days; birthweight, 3360 ± 370 gm. Divided according to placental grades, these pregnancies were found to be similar in terms of maternal age, parity, gestational age, birthweight and 5-minute Apgar scores. No difference of statistical significance was found in the pulsatility index values of the various arteries when comparing patients with placental grade 0-11 to those with grade III or pregnancies with grade 0— I to II—III (Table 1). Of group II (IUGR), 13 cases had grade III placentas and their mean gestational age at delivery was 36 weeks ± 3 days, whereas that of the control group (22 cases of group I with grade III placentas) was 39 weeks ± 6 days. The mean birthweight was 1976 ± 167 gm in the IUGR group and 3238 ± 289 gm in the control group. Table 2 demonstrates the marked difference in pulsatility index values between the two groups of grade III placentas. DISCUSSION
Tindall and Scott11 first described calcification occurring in most placentas which increased in number toward term. Ultrasound findings include progressive echogenic appearance of the placenta,1-12 along with echo-free spaces within the placental substance that develop around 20 to 24 weeks' gestation and enlarge as pregnancy advances to term. Sono-
Table 1.
January 1991
Comparative Analysis of Pulsatility Index in the Various Arteries and Placental Grades, Measured at 36 to 40 Weeks of Gestation Pulsatility Index*
Placental Placental Statistical Placental Placental Statistical
grades 0 - I I grades III significance of difference grades 0 - I grades l l - l l l significance of the difference
Arcuate Artery
Internal Carotid Artery
Umbilical Artery
0.39 ± 0.11 0.38 ± 0.15
1.36 ± 0.20 1.33 ± 0.11
0.83 ± 0.18 0.80 ± 0.16 NS 0.83 ± 0.18 0.82 ± 0.17 NS
NS
NS
0.36 ± 0.10 0.40 ± 0.13
1.41 ± 0.20 1.31 ± 0.15
NS
NS
*Mean ± standard deviation. NS: not significant.
Table 2. Comparative Analysis of Pulsatility Index in the Various Arteries, in Normal Versus iUGR Cases with Grade III Placenta at 36 to 40 Weeks of Gestation Pulsatility Index*
Normal IUGR Statistical significance of difference
48
*Mean ± standard deviation.
No.
Arcuate Artery
Internal Carotid Artery
Umbilical Artery
22 13
0.38 ± 0.15 0.66 ± 0.17 p < 0.001
1.38 ± 0.11 0.87 ± 0.09 p < 0.0001
0.79 ± 0.16 0.53 ± 0.34 p < 0.001
Downloaded by: NYU. Copyrighted material.
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
FLOW VELOCITY WAVEFORMS/Degani, et al.
9. 10. 11. 12. 13.
REFERENCES
14. Fisher CC, Garret W, Kossoff G: Placental aging monitored by grey scale echography. Am J Obstet Gynecol 124: 483-488, 1976 Spirt BA, Kagan EH, Rozanski RM: Sonolucent areas in the placenta: Sonographic and pathologic correlation. AJR 131:961-965, 1978 Haney AF, Trought WS: The sonolucent placenta in high risk obstetrics. Obstet Gynecol 55:38-41, 1980 Grannum PAT, Berkowitz RL, Hobbins JC: The ultrasonic changes in the maturing placenta and their relation to fetal pulmonic maturity. Am J Obstet Gynecol 133:915922, 1979 Petrucha RA, Platt LD: Relationship of placental grade to gestational age. Am J Obstet Gynecol 144:733-735, 1982 McCallum WD, Williams CS, Napels S, et al: Fetal blood velocity waveforms. Am J Obstet Gynecol 132:425-429, 1978 Wladimiroff JW, Tonge HM, Stewart PA: Doppler ultrasound assessment of cerebal blood flow in the human fetus. Br J Obstet Gynecol 93:471-475, 1986 Campbell S, Diaz-Recaseus J, Griffin D, et al: New doppler
15. 16.
17. 18. 19. 20. 21.
technique for assessing uteroplacental bloodflow.Lancet 1:675-677, 1983 Gosling RG, King DH: Ultrasound angiology, arteries and veins. In Marcus AW, Adamson L (eds). Edinburgh: Churchill Livingstone, 1975, pp 61-98 Brenner WE, Edelman EA, Henderick CH: A standard of fetal growth for the United States of America. Am J Obstet Gynecol 126:555-564, 1976 Tindall VR, Scott JS: Placental calcification. A study of 3025 singleton and multiple pregnancies. J Obstet Gynecol Br Commonw 72:356-373, 1965 Winsberg F: Echogenic changes with placental aging. J Clin Ultrasound 1:52-55, 1973 Petrucha RA, Golde SH, Platt LD: Real time ultrasound of the placenta in assessment of fetal pulmonic maturity. Am J Obstet Gynecol 142:463-467, 1982 Quinlan RW, Cruz AC: Ultrasonic placental grading and fetal pulmonary maturity. Am J Obstet Gynecol 142: 110-111, 1982 Tabsh KM A: Correlation of realtime ultrasonic placental grading with amniotic fluid lecithin/sphingomyelin ratio. Am J Obstet Gynecol 145:504-508, 1983 Kazzi GM, Gross TL, Sokol RJ, et al: Detection of intrauterine growth retardation: A new use for sonographic placental grading. Am J Obstet Gynecol 145:733-737, 1983 Hills D, Irwin GAL, Tuck S, et al: Distribution of placental grade in high risk gravidas. AJR 143:1011-1013, 1984 Giles WB, Trudinger BJ, Baird PJ: Fetal umbilical artery flow velocity waveforms and placental resistance: Pathological correlation. Br J Obstet Gynecol 92:31-38, 1985 McCowan LM, Mullen BM, Ritchie K: Umbilical artery flow velocity waveforms and the placental vascular bed. Am J Obstet Gynecol 157:900-902, 1987 Rightmire DA, Campbell S: Fetal and maternal doppler blood flow parameters in postterm pregnancies. Obstet Gynecol 69:891, 1987 Griffin D, Cohen-Overabeek T, Campbell S: Fetal and uteroplacental bloodflow.Clin Obstet Gynecol 10:565, 1983
Downloaded by: NYU. Copyrighted material.
assessment of these pregnancies and did not correlate with the duration of pregnancy beyond term.20-21 Using Grannum's classification a positive correlation between placental grade and gestational age was found;5 however, the tissue changes that affect the echogenicity of the maturing placenta are not directly related to vascular impedance of the placental vascular bed.
49
FETAL AND UTEROPLACENTAL FLOW VELOCITY WAVEFORMS AND PLACENTAL GRADING S. Degani, M.D., Y. Paltieli, M.D., R. Lewinsky, M.D., D. Abramovici, M.D., and M. Sharf, M.D.
ABSTRACT
Various sonographic placental changes such as patterns of calcification and echo-free spaces were correlated with advancing gestational age.1-3 In 1979, Grannum and associates4 reported the first systematic placental sonographic classification. These investigators studied the placental chorionic plate, placental substance, and basal plate in an attempt to correlate variation in sonographic appearance to fetal maturity as judged by amniotic pulmonary maturity index. Using the Grannum classification, Petrucha and Platt5 found a positive correlation between placental grade and gestational age. Anatomic and histologic correlative studies documented echogenic appearance of the placenta and subchorionic sonolucent areas representing reticular calcification1 fibrin deposition, hematoma, and cystic degeneration.3 However, the functional significance of these sonographic findings is still to be elucidated. The object of this study was to relate Doppler flow velocity waveforms in fetal, umbilical, and placental vessels to different placental grades. PATIENTS AND METHODS
A combined mechanical sector and pulsed Doppler system (Diasonics DRF 400) with a carrier frequency of 3.5 MHz was used for blood flow velocity
Downloaded by: NYU. Copyrighted material.
Doppler studies were performed on umbilical, fetal internal carotid, and arcuate arteries within 36 to 40 weeks of gestation in 85 women (66 with healthy pregnancies and 18 complicated by growth retardation), and results were analyzed by calculating the pulsatility index. In each case the placenta was examined and graded sonographically. No significant correlation was found between pulsatility index in fetal and uteroplacental vessels and placental grading in normal pregnancies. This suggests that tissue changes responsible for the echogenicity of maturing placenta are not directly related to vascular impedance of the placental vascular bed.
recordings in the internal carotid artery, umbilical artery, and arcuate arteries in 66 normal pregnancies (group I) and 18 cases of intrauterine growth retardation (IUGR; group II). All measurements were performed within 36 to 40 weeks of pregnancy. Gestational age varied between 36 and 40 weeks. The methodology used was first described by McCallum et al6 for the umbilical artery. Wladimiroff et al7 for the internal carotid artery, and Campbell et al8 for the arcuate arteries. The degree of pulsatility was quantified by calculating the pulsatility index.9 It was selected as the optimal method of analysis since results can be obtained even when the end-diastolic ratio becomes infinity or negative. The placenta was graded by the Grannum classification4 according to the most advanced portion of the placenta. The pulsatility index results were not known to the sonologist examining the grade of placenta. Group II consisted of 18 women with pregnancies complicated by severe IUGR of varying causes. All birthweights were below the 10th percentile for gestational age according to Brenner's tables, corrected for maternal parity and fetal sex.10 These charts applied to our population. Differences in pulsatility index between groups were tested using paired t test.
Ultrasound Unit, Department of Obstetrics & Gynecology, Haifa City Medical Center (Rothschild), Haifa, Israel Reprint requests: Dr. Degani, Department of Obstetrics & Gynecology, Ultrasound Unit, Haifa City Medical Center (Rothschild), P.O.B. 4940, Haifa 31048, Israel Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
47
graphic and pathologic studies (Spirt et al2) correlated calcification with advancing gestational age, which were more common in higher parity. Grannum et al4 and others13 showed fetal lung maturity with absence of respiratory distress syndrome in patients who had grade III placentas. Subsequent studies, however, have not confirmed the correlation, using Grannum's classification.14'15 Placental maturation as detected sonographically appears to be accelerated in association with IUGR,1617 consistent with the proposed concept of premature placental senescence. Giles et al18 and McCowan et al19 have demonstrated reduced mean small arterial vessel count in placentas from pregnancies with abnormal flow velocity waveform of the umbilical artery. They proposed that an increase in placental bed resistance caused by obliteration of these vessels is the primary cause of the change observed in the flow velocity waveforms of the umbilical artery. Their results show a small increase in arterial vessel count per microscope field during normal pregnancy, but the reduced flow resistance is primarily due to increase in placental size. These histologic changes are not detected by the current methods of placental grading. In our study absence of significant difference inflowvelocity waveforms between the various placental grades and normal flow patterns in grade III placentas in pregnancies not complicated by severe intrauterine growth retardation, suggest that there is no correlation between the sonographic findings and the functional changes in blood flow. Grade III placentas are more common in postdates; however (in agreement with our findings), umbilical artery velocimetry is not very useful in the
RESULTS
Clinical features of group I (66 normal pregnancies) included: mean maternal age, 26.6 ± 6 years; parity, 1.4 ± 1.1; gestational age at delivery, 39 weeks ± 3 days; birthweight, 3360 ± 370 gm. Divided according to placental grades, these pregnancies were found to be similar in terms of maternal age, parity, gestational age, birthweight and 5-minute Apgar scores. No difference of statistical significance was found in the pulsatility index values of the various arteries when comparing patients with placental grade 0-11 to those with grade III or pregnancies with grade 0— I to II—III (Table 1). Of group II (IUGR), 13 cases had grade III placentas and their mean gestational age at delivery was 36 weeks ± 3 days, whereas that of the control group (22 cases of group I with grade III placentas) was 39 weeks ± 6 days. The mean birthweight was 1976 ± 167 gm in the IUGR group and 3238 ± 289 gm in the control group. Table 2 demonstrates the marked difference in pulsatility index values between the two groups of grade III placentas. DISCUSSION
Tindall and Scott11 first described calcification occurring in most placentas which increased in number toward term. Ultrasound findings include progressive echogenic appearance of the placenta,1-12 along with echo-free spaces within the placental substance that develop around 20 to 24 weeks' gestation and enlarge as pregnancy advances to term. Sono-
Table 1.
January 1991
Comparative Analysis of Pulsatility Index in the Various Arteries and Placental Grades, Measured at 36 to 40 Weeks of Gestation Pulsatility Index*
Placental Placental Statistical Placental Placental Statistical
grades 0 - I I grades III significance of difference grades 0 - I grades l l - l l l significance of the difference
Arcuate Artery
Internal Carotid Artery
Umbilical Artery
0.39 ± 0.11 0.38 ± 0.15
1.36 ± 0.20 1.33 ± 0.11
0.83 ± 0.18 0.80 ± 0.16 NS 0.83 ± 0.18 0.82 ± 0.17 NS
NS
NS
0.36 ± 0.10 0.40 ± 0.13
1.41 ± 0.20 1.31 ± 0.15
NS
NS
*Mean ± standard deviation. NS: not significant.
Table 2. Comparative Analysis of Pulsatility Index in the Various Arteries, in Normal Versus iUGR Cases with Grade III Placenta at 36 to 40 Weeks of Gestation Pulsatility Index*
Normal IUGR Statistical significance of difference
48
*Mean ± standard deviation.
No.
Arcuate Artery
Internal Carotid Artery
Umbilical Artery
22 13
0.38 ± 0.15 0.66 ± 0.17 p < 0.001
1.38 ± 0.11 0.87 ± 0.09 p < 0.0001
0.79 ± 0.16 0.53 ± 0.34 p < 0.001
Downloaded by: NYU. Copyrighted material.
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
FLOW VELOCITY WAVEFORMS/Degani, et al.
9. 10. 11. 12. 13.
REFERENCES
14. Fisher CC, Garret W, Kossoff G: Placental aging monitored by grey scale echography. Am J Obstet Gynecol 124: 483-488, 1976 Spirt BA, Kagan EH, Rozanski RM: Sonolucent areas in the placenta: Sonographic and pathologic correlation. AJR 131:961-965, 1978 Haney AF, Trought WS: The sonolucent placenta in high risk obstetrics. Obstet Gynecol 55:38-41, 1980 Grannum PAT, Berkowitz RL, Hobbins JC: The ultrasonic changes in the maturing placenta and their relation to fetal pulmonic maturity. Am J Obstet Gynecol 133:915922, 1979 Petrucha RA, Platt LD: Relationship of placental grade to gestational age. Am J Obstet Gynecol 144:733-735, 1982 McCallum WD, Williams CS, Napels S, et al: Fetal blood velocity waveforms. Am J Obstet Gynecol 132:425-429, 1978 Wladimiroff JW, Tonge HM, Stewart PA: Doppler ultrasound assessment of cerebal blood flow in the human fetus. Br J Obstet Gynecol 93:471-475, 1986 Campbell S, Diaz-Recaseus J, Griffin D, et al: New doppler
15. 16.
17. 18. 19. 20. 21.
technique for assessing uteroplacental bloodflow.Lancet 1:675-677, 1983 Gosling RG, King DH: Ultrasound angiology, arteries and veins. In Marcus AW, Adamson L (eds). Edinburgh: Churchill Livingstone, 1975, pp 61-98 Brenner WE, Edelman EA, Henderick CH: A standard of fetal growth for the United States of America. Am J Obstet Gynecol 126:555-564, 1976 Tindall VR, Scott JS: Placental calcification. A study of 3025 singleton and multiple pregnancies. J Obstet Gynecol Br Commonw 72:356-373, 1965 Winsberg F: Echogenic changes with placental aging. J Clin Ultrasound 1:52-55, 1973 Petrucha RA, Golde SH, Platt LD: Real time ultrasound of the placenta in assessment of fetal pulmonic maturity. Am J Obstet Gynecol 142:463-467, 1982 Quinlan RW, Cruz AC: Ultrasonic placental grading and fetal pulmonary maturity. Am J Obstet Gynecol 142: 110-111, 1982 Tabsh KM A: Correlation of realtime ultrasonic placental grading with amniotic fluid lecithin/sphingomyelin ratio. Am J Obstet Gynecol 145:504-508, 1983 Kazzi GM, Gross TL, Sokol RJ, et al: Detection of intrauterine growth retardation: A new use for sonographic placental grading. Am J Obstet Gynecol 145:733-737, 1983 Hills D, Irwin GAL, Tuck S, et al: Distribution of placental grade in high risk gravidas. AJR 143:1011-1013, 1984 Giles WB, Trudinger BJ, Baird PJ: Fetal umbilical artery flow velocity waveforms and placental resistance: Pathological correlation. Br J Obstet Gynecol 92:31-38, 1985 McCowan LM, Mullen BM, Ritchie K: Umbilical artery flow velocity waveforms and the placental vascular bed. Am J Obstet Gynecol 157:900-902, 1987 Rightmire DA, Campbell S: Fetal and maternal doppler blood flow parameters in postterm pregnancies. Obstet Gynecol 69:891, 1987 Griffin D, Cohen-Overabeek T, Campbell S: Fetal and uteroplacental bloodflow.Clin Obstet Gynecol 10:565, 1983
Downloaded by: NYU. Copyrighted material.
assessment of these pregnancies and did not correlate with the duration of pregnancy beyond term.20-21 Using Grannum's classification a positive correlation between placental grade and gestational age was found;5 however, the tissue changes that affect the echogenicity of the maturing placenta are not directly related to vascular impedance of the placental vascular bed.
49
