Gynecol Obstet Invest 1990;30:139-142
© 1990 S. Karger A G , Basel 0 3 7 8 -7 3 4 6 /9 0 /0 3 0 3 -0 1 39S2.75/0
Ultrasonographic Measurement of Fetal Lung Antoine Abu Musa, Toshiyuki Hata, Kohkichi Hata, ShowaAoki, Ken Makihara, Manabu Kitao Department of Obstetrics and Gynecology, Shimane Medical University, Izumo, Japan
Key Words. Ultrasonography • Fetal lung Abstract. Fetal lung measurements were obtained by ultrasonographic examination on 103 normal pregnancies between 18 and 41 weeks’ gestation. A linear relationship between right, left and total lung circumference and gestational age was observed. The chest and heart circumference correlated well with gestational age (p < 0.001). The ratio of left lung circumference to right lung circumference remained virtually constant throughout gestation. However, the ratios of total lung circumference to chest circumference and heart circumference to chest circumfer ence increased significantly (p < 0.001) with gestational age. Introduction
Fig. 1. Cross-section of the fetal thorax with four-chamber view of the heart. Fetal lungs are seen clearly at this level. H: heart; LL: left lung; RL: right lung; Sp: spine.
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Antenatal ultrasonographic examination is now an integral part of obstetrical evaluation and management. Normograms of numerous parts of the fetal body have been developed that help to distinguish normal from abnormal development. Recently it has been reported that the measurement of fetal chest by real-time ultra sonography may be of value in prenatal diagnosis of pul monary hypoplasia [1-3]. However, the presence of a space-occupying lesion such as pleural effusion, fetal dia phragmatic hernia and chest and abdominal tumors may reduce the available space for pulmonary growth without affecting the chest dimensions. Therefore, direct mea surement of fetal lung may offer an advantage over the chest measurements. Before evaluating abnormal lung developent, we felt it necessary to carry out a cross-sectional prospective study to determine the normal relation between lung measurement and menstrual age using real-time ultra sonography. To our knowledge, this is the first report of fetal lung growth during normal pregnancy.
Abu Musa/Hata/Hata/Aoki/Makihara/Kitao
140
The study group consisted of 103 patients between 18 and 41 weeks’ gestation chosen for analysis on the basis of the following criteria: (1) a history of regular menses; (2) known date of the begin ning of the last menstrual period; (3) close relationship between menstrual age and gestational age based on ultrasonographic assess ment of the crown-rump length or biparietal diameter and femur length; (4) absence of maternal disease known to affect normal fetal growth (e.g., diabetes mellitus), and (5) absence of fetal anomalies, intrauterine growth retardation and oligohydramnios. Each fetus was measured only once during gestation. All patients delivered in our hospital and the outcome data were evaluated to ensure that the pregnancies were normal. All examinations were performed using a linear array real-time system or mechanical sector scanner, with a 3.5-MHz focused trans ducer (Aloka SSD-256 and SSD-650, and Sonovista-SL). The ana tomic plane chosen for fetal lung measurement was a cross-sectional view of the fetal chest at right angles to the fetal spine at a level in which a four-chamber view of the heart was visualized (fig. 1). In
this section the circumferences of the left lung, right lung, chest and heart were made from a Polaroid image by one investigator (A.A.M.) using an electronic digitizer (NEC-PC 8001 mk II); the lung measurements were made along the outer perimeter. The relationship between gestational age in weeks to each of these measurements was analyzed by simple linear regression and the coefficient of determination was calculated. Also assessed by this method was the relationship between gestational age and total lung circumference and the ratios of the following parameters: total lung circumference to chest circumference, and heart circumference to chest circumference.
Results The relationships of left lung, right lung and total lung circumferences to gestational age were observed to be linear (fig. 2-4). The most clinically useful correlation was with total lung circumference (r2 = 0.859). Similar
Fig. 2. Relationship between left lung cir cumference and gestational age.
Fig. 3. Relationship between right lung cir cumference and gestational age.
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Materials and Methods
141
Fetal Lung Measurement by Ultrasonography
Fig. 4. Relationship between total lung cir cumference and gestational age.
Fig. 5. Relationship between the ratio of total lung circumference to chest circumfer ence and gestational age.
Fig. 6. Relationship between the ratio of heart circumference to chest circumference and gestational age.
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o
142
Discussion In this study a linear relationship between lung cir cumference and gestational age in normal fetuses was demonstrated. The most clinically useful correlation was seen with the total lung circumference. The well-defined anatomical plane used for the measurements is easily reproducible. In addition, with the sharply defined images that can be obtained with current ultrasono graphic equipment the contour of both lungs can be eas ily recognized. In agreement with the observations made by other investigators [1, 4], a linear relationship between chest circumference and gestational age was noted. Antenatal measurements of chest circumference have been used to predict pulmonary hypoplasia [1-3], However, the highly predictive values of this technique were noted only when the contents of the chest were mainly lung and heart [1]. Nimrod et al. [2] pointed out the inability of fetal chest circumference measurement to assess pulmo nary hypoplasia in association with pleural effusion. Fong et al. [3] reported a case of pulmonary hypoplasia with normal chest circumference. The infant had mark edly wrinkled skin which might have accounted for the normal chest circumference value. Pulmonary hypopla sia results when adequate lung growth is hindered [5]. This situation may result from a space-occupying factor such as pleural effusion, fetal diaphragmatic hernia and chest and abdominal tumors, that may reduce the avail able space for pulmonary growth. In such situations, the
fetal chest circumference may be within the normal range. Therefore, direct measurement of lung circumfer ence might be a better predictor of pulmonary hypopla sia. Another observation noted in this study was the rela tionship between gestational age and the ratios of total lung circumference to chest circumference and heart cir cumference to chest circumference. These ratios in creased gradually with increasing gestation. On the other hand, left lung circumference to right lung circumference ratio remained almost constant throughout gestation. Significant deviations in these ratios from the expected values might be helpful in further evaluation of fetal growth. In conclusion, this is the first report of direct fetal lung measurement by real-time ultrasonography. The predictive ability of ultrasonographic estimation of lung circumference in relation to pulmonary hypoplasia is being investigated in a currently ongoing, prospective study of pregnancies at risk of this condition.
References 1 Nimrod C, Davis D, Iwanicki S, et al: Ultrasound prediction of pulmonary hypoplasia. Obstet Gynecol 1986;68:495-497. 2 Nimrod C, Nicholson S, Davis D, et al: Pulmonary hypoplasia testing in clinical obstetrics. Am J Obstet Gynecol 1988:158: 277-280. 3 Fong K, Ohlsson A, Zalev A: Fetal thoracic circumference: A prospective cross-sectional study with real-time ultrasound. Am J Obstet Gynecol 1988; 158:1154-1160. 4 Chitkara U, Rosenberg J, Chervenak FA, et al: Prenatal sono graphic assessment of the fetal thorax: Normal values. Am J Obstet Gynecol 1987; 156:1069-1074. 5 Kitterman JA: Fetal lung development. J Dev Physiol 1984;6: 67-82.
Received: March 20, 1990 Accepted: April 5, 1990 Toshiyuki Hata, MD Department of Obstetrics and Gynecology Shimane Medical University Izumo 693 (Japan)
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correlation between chest and heart circumferences ver sus gestational age was noted (r2 = 0.906 and r2 = 0.837, respectively). The parameters measured were also as sessed as ratios. The ratio of left lung circumference to right lung circumference remained virtually constant throughout gestation. The total lung circumference to chest circumference ratio gradually increased (p < 0.001) from 0.83 at 18 weeks to 1.00 at 41 weeks (fig. 5). Moreover, a significant increase (p < 0.001) in the ratio of heart circumference to chest circumference from 0.37 at 18 weeks to 0.46 at 41 weeks was noted (fig. 6).
Abu Musa/Hata/Hata/Aoki/Makihara/Kitao
© 1990 S. Karger A G , Basel 0 3 7 8 -7 3 4 6 /9 0 /0 3 0 3 -0 1 39S2.75/0
Ultrasonographic Measurement of Fetal Lung Antoine Abu Musa, Toshiyuki Hata, Kohkichi Hata, ShowaAoki, Ken Makihara, Manabu Kitao Department of Obstetrics and Gynecology, Shimane Medical University, Izumo, Japan
Key Words. Ultrasonography • Fetal lung Abstract. Fetal lung measurements were obtained by ultrasonographic examination on 103 normal pregnancies between 18 and 41 weeks’ gestation. A linear relationship between right, left and total lung circumference and gestational age was observed. The chest and heart circumference correlated well with gestational age (p < 0.001). The ratio of left lung circumference to right lung circumference remained virtually constant throughout gestation. However, the ratios of total lung circumference to chest circumference and heart circumference to chest circumfer ence increased significantly (p < 0.001) with gestational age. Introduction
Fig. 1. Cross-section of the fetal thorax with four-chamber view of the heart. Fetal lungs are seen clearly at this level. H: heart; LL: left lung; RL: right lung; Sp: spine.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/16/2018 6:36:03 AM
Antenatal ultrasonographic examination is now an integral part of obstetrical evaluation and management. Normograms of numerous parts of the fetal body have been developed that help to distinguish normal from abnormal development. Recently it has been reported that the measurement of fetal chest by real-time ultra sonography may be of value in prenatal diagnosis of pul monary hypoplasia [1-3]. However, the presence of a space-occupying lesion such as pleural effusion, fetal dia phragmatic hernia and chest and abdominal tumors may reduce the available space for pulmonary growth without affecting the chest dimensions. Therefore, direct mea surement of fetal lung may offer an advantage over the chest measurements. Before evaluating abnormal lung developent, we felt it necessary to carry out a cross-sectional prospective study to determine the normal relation between lung measurement and menstrual age using real-time ultra sonography. To our knowledge, this is the first report of fetal lung growth during normal pregnancy.
Abu Musa/Hata/Hata/Aoki/Makihara/Kitao
140
The study group consisted of 103 patients between 18 and 41 weeks’ gestation chosen for analysis on the basis of the following criteria: (1) a history of regular menses; (2) known date of the begin ning of the last menstrual period; (3) close relationship between menstrual age and gestational age based on ultrasonographic assess ment of the crown-rump length or biparietal diameter and femur length; (4) absence of maternal disease known to affect normal fetal growth (e.g., diabetes mellitus), and (5) absence of fetal anomalies, intrauterine growth retardation and oligohydramnios. Each fetus was measured only once during gestation. All patients delivered in our hospital and the outcome data were evaluated to ensure that the pregnancies were normal. All examinations were performed using a linear array real-time system or mechanical sector scanner, with a 3.5-MHz focused trans ducer (Aloka SSD-256 and SSD-650, and Sonovista-SL). The ana tomic plane chosen for fetal lung measurement was a cross-sectional view of the fetal chest at right angles to the fetal spine at a level in which a four-chamber view of the heart was visualized (fig. 1). In
this section the circumferences of the left lung, right lung, chest and heart were made from a Polaroid image by one investigator (A.A.M.) using an electronic digitizer (NEC-PC 8001 mk II); the lung measurements were made along the outer perimeter. The relationship between gestational age in weeks to each of these measurements was analyzed by simple linear regression and the coefficient of determination was calculated. Also assessed by this method was the relationship between gestational age and total lung circumference and the ratios of the following parameters: total lung circumference to chest circumference, and heart circumference to chest circumference.
Results The relationships of left lung, right lung and total lung circumferences to gestational age were observed to be linear (fig. 2-4). The most clinically useful correlation was with total lung circumference (r2 = 0.859). Similar
Fig. 2. Relationship between left lung cir cumference and gestational age.
Fig. 3. Relationship between right lung cir cumference and gestational age.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/16/2018 6:36:03 AM
Materials and Methods
141
Fetal Lung Measurement by Ultrasonography
Fig. 4. Relationship between total lung cir cumference and gestational age.
Fig. 5. Relationship between the ratio of total lung circumference to chest circumfer ence and gestational age.
Fig. 6. Relationship between the ratio of heart circumference to chest circumference and gestational age.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/16/2018 6:36:03 AM
o
142
Discussion In this study a linear relationship between lung cir cumference and gestational age in normal fetuses was demonstrated. The most clinically useful correlation was seen with the total lung circumference. The well-defined anatomical plane used for the measurements is easily reproducible. In addition, with the sharply defined images that can be obtained with current ultrasono graphic equipment the contour of both lungs can be eas ily recognized. In agreement with the observations made by other investigators [1, 4], a linear relationship between chest circumference and gestational age was noted. Antenatal measurements of chest circumference have been used to predict pulmonary hypoplasia [1-3], However, the highly predictive values of this technique were noted only when the contents of the chest were mainly lung and heart [1]. Nimrod et al. [2] pointed out the inability of fetal chest circumference measurement to assess pulmo nary hypoplasia in association with pleural effusion. Fong et al. [3] reported a case of pulmonary hypoplasia with normal chest circumference. The infant had mark edly wrinkled skin which might have accounted for the normal chest circumference value. Pulmonary hypopla sia results when adequate lung growth is hindered [5]. This situation may result from a space-occupying factor such as pleural effusion, fetal diaphragmatic hernia and chest and abdominal tumors, that may reduce the avail able space for pulmonary growth. In such situations, the
fetal chest circumference may be within the normal range. Therefore, direct measurement of lung circumfer ence might be a better predictor of pulmonary hypopla sia. Another observation noted in this study was the rela tionship between gestational age and the ratios of total lung circumference to chest circumference and heart cir cumference to chest circumference. These ratios in creased gradually with increasing gestation. On the other hand, left lung circumference to right lung circumference ratio remained almost constant throughout gestation. Significant deviations in these ratios from the expected values might be helpful in further evaluation of fetal growth. In conclusion, this is the first report of direct fetal lung measurement by real-time ultrasonography. The predictive ability of ultrasonographic estimation of lung circumference in relation to pulmonary hypoplasia is being investigated in a currently ongoing, prospective study of pregnancies at risk of this condition.
References 1 Nimrod C, Davis D, Iwanicki S, et al: Ultrasound prediction of pulmonary hypoplasia. Obstet Gynecol 1986;68:495-497. 2 Nimrod C, Nicholson S, Davis D, et al: Pulmonary hypoplasia testing in clinical obstetrics. Am J Obstet Gynecol 1988:158: 277-280. 3 Fong K, Ohlsson A, Zalev A: Fetal thoracic circumference: A prospective cross-sectional study with real-time ultrasound. Am J Obstet Gynecol 1988; 158:1154-1160. 4 Chitkara U, Rosenberg J, Chervenak FA, et al: Prenatal sono graphic assessment of the fetal thorax: Normal values. Am J Obstet Gynecol 1987; 156:1069-1074. 5 Kitterman JA: Fetal lung development. J Dev Physiol 1984;6: 67-82.
Received: March 20, 1990 Accepted: April 5, 1990 Toshiyuki Hata, MD Department of Obstetrics and Gynecology Shimane Medical University Izumo 693 (Japan)
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/16/2018 6:36:03 AM
correlation between chest and heart circumferences ver sus gestational age was noted (r2 = 0.906 and r2 = 0.837, respectively). The parameters measured were also as sessed as ratios. The ratio of left lung circumference to right lung circumference remained virtually constant throughout gestation. The total lung circumference to chest circumference ratio gradually increased (p < 0.001) from 0.83 at 18 weeks to 1.00 at 41 weeks (fig. 5). Moreover, a significant increase (p < 0.001) in the ratio of heart circumference to chest circumference from 0.37 at 18 weeks to 0.46 at 41 weeks was noted (fig. 6).
Abu Musa/Hata/Hata/Aoki/Makihara/Kitao
