Int J Gynecol
International
Obstet, 1992, 38: 87-91 Federation of Gynecology
Fetal binocular T. Tongsonga, Departments
87 and Obstetrics
distance as a predictor of menstrual S. Jesadapornchai”
C. Wanapirak”,
of UObstetrics
and Gynecology
and ‘Pediatrics,
Faculty
age
and E. Tathayathikomb
of Medicine.
Chiang
Mai
University.
Chiang
Mai
I Thuilund)
(Received September 27th, 1991) (Revised and accepted December 2nd. 1991)
Abstract The relation between fetal binocular distance and menstrual age was determined by crosssectional analysis of 555 normalfetuses (14-40 weeks) using real-time sonography. Mathematical modelling of the data demonstrated that the binocular distance growth curve, similar to the biparietal diameter, is nonlinear. Predicted binocular values at various points in gestation were comparable to the results of other investigators. Predicted menstrual age in weeks for spect& binocular distance measurements in millimeters were calculated and are reported in tabular form. The variability ( &2 SD) associated with predicting menstrual age from binocular distance is f 14 days between 14 and 27 weeks, but between 29 and 40 weeks the variability is &24 days. Binocular distance can be used as an adjunct in estimating menstrual age and may be useful in the diagnosis of some abnormalities, e.g. hypotelorism or hypertelorism.
Keywords: Binocular distance; Menstrual age; Ultrasound. Introduction With substantially improved sonograghical imaging, the fetal binocular distance (BN) can be identified and measured in utero using real-time sonography from early pregnancy, 0020-7292/92/$05.00
0 1992 lnternational Federation Printed and Published in Ireland
and normal values have been reported both as a function of gestational age and biparietal diameter [ 1,2]. The standard measurements for dating pregnancies, i.e. biparietal diameter, femur head circumference have been length, numerously reported [3,4] but the standard values of binocular distance have been studied very little. The objectives of this study may be summarized as: (i) to determine the normal relationship between binocular distance (BN) and gestational age ( &2 SD) measured using realtime ultrasound; (ii) to provide baseline data for use in predicting menstrual age and in screening some orbital anomalies. This study evaluated further the variability (&2 SD) associated with predicting menstrual age from binocular distance (BN) particularly during the second half of gestation when the biparietal diameter may be less accurate [5]. Patients and methods This cross-sectional study consisted of 555 normal pregnant women attending the antenatal clinic at Maharaj Nakorn Chiang Mai Hospital between 14 and 40 weeks from May 1988 until July 1991. The subjects had to meet the following criteria: (i) history of regular menstruation and knowledge of the exact date of the last menstrual period; (ii) singleton pregnancy without medical or obstetrical complication, no evidence of intrauterine Article
of Gynecology
and Obstetrics
88
Tongsong et al.
growth retardation and congenital anomalies; (iii) attending the antenatal clinic within the first trimester of pregnancy and menstrual age consistent with clinical estimation; and (iv) Dubowitz scores must be assessed and the scores must confirm gestational age calculated from date. Each patient was voluntary enrolled into the study without any specific indications. The measurement was performed only once for each patient. All scanning was done with an Aloka model SSD 650 scanner with a transducer frequency of 3.5 MHz. The fetal outer binocular distance was identified in the occipitotransverse or occipitoposterior fetal positions as described by Mayden et al. [l]. With the head in the occipitotransverse position, the transducer can
Table 1.
Mean fetal BN with standard
deviation,
be placed in two possible planes: (1) along the coronal plane, approximately 2 cm posterior to the glabella-alveolar line, or (2) along the orbitomental line, approximately 2-3 cm below the level of the biparietal diameter. In both of these views, the midline, orbital rings, nasal processes, and portions of the maxillae can be demonstrated. With the head in the occipitoposterior position, the transducer was placed in a plane that transected the occiput, orbits, and nasal processes. Measurements were obtained only when the fetal face was directly perpendicular to the uterine wall, since measurements in an oblique plane were considered to be unreliable. The outer orbital diameter was measured by means of electronic calipers from the lateral border of the orbit to the opposite lateral
5th, SOth, and 95th percentile
for GA.
GA week
No. of exam. (n)
Mean
SD
(cm)
(cm)
5th percentile
50th percentile
95th percentile
14 15
19 20
1.91 2.15
0.25 0.25
1.60 1.70
1.90 2.10
2.30 2.35
16 17 18 19
20 20 22 20
20 21 22 23
21 22 20 20
2.24 2.55 2.78 2.97 3.07 3.29 3.46 3.67
1.71 2.10 2.30 2.56 2.70 2.85 3.02 3.21
24 25 26 27
21 22 19 20
3.77 4.03 4.16 4.33
0.24 0.21 0.27 0.25 0.21 0.23 0.19 0.22 0.27 0.23 0.21 0.24
28 29 30 31
20 22 21 21
4.49 4.67 4.76 4.98
0.22 0.24 0.21 0.26
32 33 34 35 36 37 38 39
22 20 21 22
5.05 5.17 5.39 5.46
19 20 20 20
40
21
Int J Gynecol Obstet 38
2.31 ,2.51 2.81 3.00 3.10 3.25 3.50 3.66 3.75 4.06 4.15 4.31
4.27 4.40 4.58 4.75
4.52 4.61 4.79 5.04
5.03 5.19 5.23 5.40
5.56 5.65 5.81 5.82
0.20 0.23 0.26 0.23 0.24 0.27 0.28 0.27
4.10 4.30 4.41 4.50 4.71 4.73 4.85 4.95 5.02 5.09 5.31 5.32
5.12 5.20 5.41 5.60 5.62 5.70 5.80 5.90
5.40 5.63 5.82 6.05 5.95 6.10 6.24 6.29
5.95
0.27
5.40
6.00
6.40
3.48 3.60 3.82 3.95
2.69 2.80 3.24 3.53 3.54 3.74 3.80 4.01
Binocular distance
border (outer to outer). Each measurement was obtained from the average of the three best measurements obtained at each examination. All examinations were performed by the author (perinatal sonographer) who did not know the menstrual age of the patients. Dubowitz scores were assessed by only one pediatrician who had no prior obstetric information. The data collected were stored in a microcomputer and subsequently analyzed. Results A total of 555 measurements of BN (binocular distance) were obtained from 555 normal Thai pregnant women. The mean BN and standard deviation for each gestational week are calculated and shown in Table 1 and Fig. 1. Additionally, 5th, 50th, 95th percentiles are also shown in Table 1 and Fig. 1. There is a progressive increase from the second trimester towards term. Linear quadratic function could be considered an optimal model for predicting menstrual age from BN. 7 T
89
(r2 = 0.94052, P = 0.000). The regression equation for these data is gestational age (weeks) = 6.54398 + 3.4659(BN) + 0.30682( BN’). Predicted menstrual age values for specific BN measurements are indicated in Table 2. For BN (cm) as a dependent variable and gestational age (weeks) as an independent variable, the equation (r2 = 0.94724, P = (BN = - 1.64022 + 0.28562(AGW) 0.000). - 0.0023768 AGW2)). The predicted BN value for a given gestational week based on the quadratic function was determined and shown in Table 3. In comparison with other studies, the BN growth pattern was consistent with sonographic studies of the western investigators [l-3] throughout pregnancy. The variability (~2 SD) associated with predicting menstrual age from binocular distance is f 14 days between 14 and 27 weeks, but between 29 and 40 weeks the variability is *24 days. Discussion The predicted binocular diameters at various points in gestation agree relatively well with the values reported by others [1,2].
1
6 t
Table 2. BN
9 Mean
Gestational Age Fig. 1. Mean and standard tional week.
-
Mean
-
t&ml-
??
*SD.
250.
(weeks)
deviation
of BN for each gesta-
Predicted
menstrual
age for biocular
distances.
(cm)
GA (weeks)
BN (cm)
GA (weeks)
BN (cm)
GA (weeks)
1.6 1.7
12.8 13.3
3.2 3.3
20.80 21.34
4.8 4.9
30.29 30.94
1.8 1.9 2.0 2.1
13.78 14.24 14.71 IS.18
3.4 3.5 3.6 3.7
5.0 5.1 5.2 5.3
31.59 32.25 32.91 33.58
2.2 2.3 2.4 2.5
3.8 3.9 4.0 4.1
2.6 2.7 2.8 2.9
15.66 16.15 16.64 17.14 17.64 18.15 18.67 19.19
21.90 22.46 23.02 23.59 24.17 24.76 25.35 25.94
4.2 4.3 4.4 4.5
26.54 27.15 27.77 28.39
5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.1
34.26 34.94 35.63 36.33 37.03 37.74 38.45 39.17
3.0 3.1
19.72 20.25
4.6 4.7
29.02 29.65
6.2 6.3
39.90 40.63
Arficle
90
Tongsong et al.
Table 3.
Predicted
GA (week)
(cm)
14 15
1.9 2.1
16 17 18 19
mean BN (cm) for each gestational
BN
week.
BN
GA (week)
(cm)
2.3 2.5 2.7 2.9
28 29 30 31 32 33
4.5 4.6 4.8 4.9 5.1 5.2
20 21 22 23
3.1 3.3 3.5 3.7
34 35 36 37
5.3 5.4 5.6 5.7
24 25 26 27
3.8 4.0 4.2 4.3
38 39 40
5.8 5.9 6.0
An excellent correlation was found to exist between binocular diameter and gestational age. As is true of all measurements made with ultrasound, binocular distance must be performed precisely or the data will be misleading. For example, tangential cuts through the orbits can easily produce er-
roneous measurements. Also, it is occasionally difficult to define accurately the distal orbital margin in the occipital transverse position because of acoustic shadowing from the nose. Nevertheless, despite these pitfalls, we have found this technique to be valuable in evaluating gestational age and essential in assessing fetal orbital architecture in patients at risk for ocular abnormalities. The binocular distance is a parameter that has occasionally proven useful in our practice. To obtain the right plane, one should start from the conventional section of the BPD and move the transducer caudally until the orbits are visualized. In the correct plane, both eyes should have the same diameter, and the image should be symmetrical. The largest diameter of eye should be used; the interocular distance should be the smallest. Our fetal BN growth patterns agree relatively well with those of western studies [1,2] although the actual values in this study are somewhat lower in early pregnancy. This finding indicates that racial factors have only minimal effect on binocular growth. We hope that the values from this study provide useful baseline data for the evaluation of fetal BN growth in our population, since they are more appropriate for application with Thai women than those of Caucasian studies. In addition, these data may also serve as an adjunct parameter in predicting menstrual age, especially in cases where biparietal diameter could not be obtained, or in abnormal head shape where biparietal diameter may prove to be unreliable or virtually impossible to obtain when the fetal head is facing straight up or down. In these cases, however, orbits can be identified and binocular diameters can be used to date pregnancies in lieu of biparietal diameter measurements. Additionally, fetal BN may be useful in diagnosis of some abnormalities, e.g. hypotelorism or hypertelorism. References 1
In1 J Gynecol Obstet 38
Mayden Hobbins
KL, Tortora JC: Orbital
M, Berkowitz RL, Bracken diameter: a new parameter
M. for
Binocular distance
2
3
prenatal diagnosis and dating. Am J Obstet Gynecol 144: 289, 1982. Jeanty P. Cantraine F, Cousaert E et al: The binocular distance: a new parameter to estimate fetal age. J Ultrasound Med 3: 241, 1984b. Jeanty P: Fetal biometry. In: The principles and Practice of Ultrasonography in Obstetrics and Gynecology (eds AC Fleischer, R Romero, F Manning, P Jeanty, AE James), pp 93-108. Appleton & Lange, East Norwalk. 1991.
4
5
91
Kurtz AB, Needleman L: Ultrasound assessment of fetal age. In: Ultrasonography in Obstetrics and Gynecology (ed PW Callen), pp 47-63. WB Saunders, Philadelphia, 1988. Sabbhaga RE, Hughey M: Standardization of sonar cephalometry and gestational age. Obstet Gynecol 52: 402, 1978.
Article
International
Obstet, 1992, 38: 87-91 Federation of Gynecology
Fetal binocular T. Tongsonga, Departments
87 and Obstetrics
distance as a predictor of menstrual S. Jesadapornchai”
C. Wanapirak”,
of UObstetrics
and Gynecology
and ‘Pediatrics,
Faculty
age
and E. Tathayathikomb
of Medicine.
Chiang
Mai
University.
Chiang
Mai
I Thuilund)
(Received September 27th, 1991) (Revised and accepted December 2nd. 1991)
Abstract The relation between fetal binocular distance and menstrual age was determined by crosssectional analysis of 555 normalfetuses (14-40 weeks) using real-time sonography. Mathematical modelling of the data demonstrated that the binocular distance growth curve, similar to the biparietal diameter, is nonlinear. Predicted binocular values at various points in gestation were comparable to the results of other investigators. Predicted menstrual age in weeks for spect& binocular distance measurements in millimeters were calculated and are reported in tabular form. The variability ( &2 SD) associated with predicting menstrual age from binocular distance is f 14 days between 14 and 27 weeks, but between 29 and 40 weeks the variability is &24 days. Binocular distance can be used as an adjunct in estimating menstrual age and may be useful in the diagnosis of some abnormalities, e.g. hypotelorism or hypertelorism.
Keywords: Binocular distance; Menstrual age; Ultrasound. Introduction With substantially improved sonograghical imaging, the fetal binocular distance (BN) can be identified and measured in utero using real-time sonography from early pregnancy, 0020-7292/92/$05.00
0 1992 lnternational Federation Printed and Published in Ireland
and normal values have been reported both as a function of gestational age and biparietal diameter [ 1,2]. The standard measurements for dating pregnancies, i.e. biparietal diameter, femur head circumference have been length, numerously reported [3,4] but the standard values of binocular distance have been studied very little. The objectives of this study may be summarized as: (i) to determine the normal relationship between binocular distance (BN) and gestational age ( &2 SD) measured using realtime ultrasound; (ii) to provide baseline data for use in predicting menstrual age and in screening some orbital anomalies. This study evaluated further the variability (&2 SD) associated with predicting menstrual age from binocular distance (BN) particularly during the second half of gestation when the biparietal diameter may be less accurate [5]. Patients and methods This cross-sectional study consisted of 555 normal pregnant women attending the antenatal clinic at Maharaj Nakorn Chiang Mai Hospital between 14 and 40 weeks from May 1988 until July 1991. The subjects had to meet the following criteria: (i) history of regular menstruation and knowledge of the exact date of the last menstrual period; (ii) singleton pregnancy without medical or obstetrical complication, no evidence of intrauterine Article
of Gynecology
and Obstetrics
88
Tongsong et al.
growth retardation and congenital anomalies; (iii) attending the antenatal clinic within the first trimester of pregnancy and menstrual age consistent with clinical estimation; and (iv) Dubowitz scores must be assessed and the scores must confirm gestational age calculated from date. Each patient was voluntary enrolled into the study without any specific indications. The measurement was performed only once for each patient. All scanning was done with an Aloka model SSD 650 scanner with a transducer frequency of 3.5 MHz. The fetal outer binocular distance was identified in the occipitotransverse or occipitoposterior fetal positions as described by Mayden et al. [l]. With the head in the occipitotransverse position, the transducer can
Table 1.
Mean fetal BN with standard
deviation,
be placed in two possible planes: (1) along the coronal plane, approximately 2 cm posterior to the glabella-alveolar line, or (2) along the orbitomental line, approximately 2-3 cm below the level of the biparietal diameter. In both of these views, the midline, orbital rings, nasal processes, and portions of the maxillae can be demonstrated. With the head in the occipitoposterior position, the transducer was placed in a plane that transected the occiput, orbits, and nasal processes. Measurements were obtained only when the fetal face was directly perpendicular to the uterine wall, since measurements in an oblique plane were considered to be unreliable. The outer orbital diameter was measured by means of electronic calipers from the lateral border of the orbit to the opposite lateral
5th, SOth, and 95th percentile
for GA.
GA week
No. of exam. (n)
Mean
SD
(cm)
(cm)
5th percentile
50th percentile
95th percentile
14 15
19 20
1.91 2.15
0.25 0.25
1.60 1.70
1.90 2.10
2.30 2.35
16 17 18 19
20 20 22 20
20 21 22 23
21 22 20 20
2.24 2.55 2.78 2.97 3.07 3.29 3.46 3.67
1.71 2.10 2.30 2.56 2.70 2.85 3.02 3.21
24 25 26 27
21 22 19 20
3.77 4.03 4.16 4.33
0.24 0.21 0.27 0.25 0.21 0.23 0.19 0.22 0.27 0.23 0.21 0.24
28 29 30 31
20 22 21 21
4.49 4.67 4.76 4.98
0.22 0.24 0.21 0.26
32 33 34 35 36 37 38 39
22 20 21 22
5.05 5.17 5.39 5.46
19 20 20 20
40
21
Int J Gynecol Obstet 38
2.31 ,2.51 2.81 3.00 3.10 3.25 3.50 3.66 3.75 4.06 4.15 4.31
4.27 4.40 4.58 4.75
4.52 4.61 4.79 5.04
5.03 5.19 5.23 5.40
5.56 5.65 5.81 5.82
0.20 0.23 0.26 0.23 0.24 0.27 0.28 0.27
4.10 4.30 4.41 4.50 4.71 4.73 4.85 4.95 5.02 5.09 5.31 5.32
5.12 5.20 5.41 5.60 5.62 5.70 5.80 5.90
5.40 5.63 5.82 6.05 5.95 6.10 6.24 6.29
5.95
0.27
5.40
6.00
6.40
3.48 3.60 3.82 3.95
2.69 2.80 3.24 3.53 3.54 3.74 3.80 4.01
Binocular distance
border (outer to outer). Each measurement was obtained from the average of the three best measurements obtained at each examination. All examinations were performed by the author (perinatal sonographer) who did not know the menstrual age of the patients. Dubowitz scores were assessed by only one pediatrician who had no prior obstetric information. The data collected were stored in a microcomputer and subsequently analyzed. Results A total of 555 measurements of BN (binocular distance) were obtained from 555 normal Thai pregnant women. The mean BN and standard deviation for each gestational week are calculated and shown in Table 1 and Fig. 1. Additionally, 5th, 50th, 95th percentiles are also shown in Table 1 and Fig. 1. There is a progressive increase from the second trimester towards term. Linear quadratic function could be considered an optimal model for predicting menstrual age from BN. 7 T
89
(r2 = 0.94052, P = 0.000). The regression equation for these data is gestational age (weeks) = 6.54398 + 3.4659(BN) + 0.30682( BN’). Predicted menstrual age values for specific BN measurements are indicated in Table 2. For BN (cm) as a dependent variable and gestational age (weeks) as an independent variable, the equation (r2 = 0.94724, P = (BN = - 1.64022 + 0.28562(AGW) 0.000). - 0.0023768 AGW2)). The predicted BN value for a given gestational week based on the quadratic function was determined and shown in Table 3. In comparison with other studies, the BN growth pattern was consistent with sonographic studies of the western investigators [l-3] throughout pregnancy. The variability (~2 SD) associated with predicting menstrual age from binocular distance is f 14 days between 14 and 27 weeks, but between 29 and 40 weeks the variability is *24 days. Discussion The predicted binocular diameters at various points in gestation agree relatively well with the values reported by others [1,2].
1
6 t
Table 2. BN
9 Mean
Gestational Age Fig. 1. Mean and standard tional week.
-
Mean
-
t&ml-
??
*SD.
250.
(weeks)
deviation
of BN for each gesta-
Predicted
menstrual
age for biocular
distances.
(cm)
GA (weeks)
BN (cm)
GA (weeks)
BN (cm)
GA (weeks)
1.6 1.7
12.8 13.3
3.2 3.3
20.80 21.34
4.8 4.9
30.29 30.94
1.8 1.9 2.0 2.1
13.78 14.24 14.71 IS.18
3.4 3.5 3.6 3.7
5.0 5.1 5.2 5.3
31.59 32.25 32.91 33.58
2.2 2.3 2.4 2.5
3.8 3.9 4.0 4.1
2.6 2.7 2.8 2.9
15.66 16.15 16.64 17.14 17.64 18.15 18.67 19.19
21.90 22.46 23.02 23.59 24.17 24.76 25.35 25.94
4.2 4.3 4.4 4.5
26.54 27.15 27.77 28.39
5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.1
34.26 34.94 35.63 36.33 37.03 37.74 38.45 39.17
3.0 3.1
19.72 20.25
4.6 4.7
29.02 29.65
6.2 6.3
39.90 40.63
Arficle
90
Tongsong et al.
Table 3.
Predicted
GA (week)
(cm)
14 15
1.9 2.1
16 17 18 19
mean BN (cm) for each gestational
BN
week.
BN
GA (week)
(cm)
2.3 2.5 2.7 2.9
28 29 30 31 32 33
4.5 4.6 4.8 4.9 5.1 5.2
20 21 22 23
3.1 3.3 3.5 3.7
34 35 36 37
5.3 5.4 5.6 5.7
24 25 26 27
3.8 4.0 4.2 4.3
38 39 40
5.8 5.9 6.0
An excellent correlation was found to exist between binocular diameter and gestational age. As is true of all measurements made with ultrasound, binocular distance must be performed precisely or the data will be misleading. For example, tangential cuts through the orbits can easily produce er-
roneous measurements. Also, it is occasionally difficult to define accurately the distal orbital margin in the occipital transverse position because of acoustic shadowing from the nose. Nevertheless, despite these pitfalls, we have found this technique to be valuable in evaluating gestational age and essential in assessing fetal orbital architecture in patients at risk for ocular abnormalities. The binocular distance is a parameter that has occasionally proven useful in our practice. To obtain the right plane, one should start from the conventional section of the BPD and move the transducer caudally until the orbits are visualized. In the correct plane, both eyes should have the same diameter, and the image should be symmetrical. The largest diameter of eye should be used; the interocular distance should be the smallest. Our fetal BN growth patterns agree relatively well with those of western studies [1,2] although the actual values in this study are somewhat lower in early pregnancy. This finding indicates that racial factors have only minimal effect on binocular growth. We hope that the values from this study provide useful baseline data for the evaluation of fetal BN growth in our population, since they are more appropriate for application with Thai women than those of Caucasian studies. In addition, these data may also serve as an adjunct parameter in predicting menstrual age, especially in cases where biparietal diameter could not be obtained, or in abnormal head shape where biparietal diameter may prove to be unreliable or virtually impossible to obtain when the fetal head is facing straight up or down. In these cases, however, orbits can be identified and binocular diameters can be used to date pregnancies in lieu of biparietal diameter measurements. Additionally, fetal BN may be useful in diagnosis of some abnormalities, e.g. hypotelorism or hypertelorism. References 1
In1 J Gynecol Obstet 38
Mayden Hobbins
KL, Tortora JC: Orbital
M, Berkowitz RL, Bracken diameter: a new parameter
M. for
Binocular distance
2
3
prenatal diagnosis and dating. Am J Obstet Gynecol 144: 289, 1982. Jeanty P. Cantraine F, Cousaert E et al: The binocular distance: a new parameter to estimate fetal age. J Ultrasound Med 3: 241, 1984b. Jeanty P: Fetal biometry. In: The principles and Practice of Ultrasonography in Obstetrics and Gynecology (eds AC Fleischer, R Romero, F Manning, P Jeanty, AE James), pp 93-108. Appleton & Lange, East Norwalk. 1991.
4
5
91
Kurtz AB, Needleman L: Ultrasound assessment of fetal age. In: Ultrasonography in Obstetrics and Gynecology (ed PW Callen), pp 47-63. WB Saunders, Philadelphia, 1988. Sabbhaga RE, Hughey M: Standardization of sonar cephalometry and gestational age. Obstet Gynecol 52: 402, 1978.
Article
