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Ultrasonic assessment of fetal head and body sizes in relation to normal and retarded fetal growth
OBSTETRICS
Ultrasonic assessment of fetal head and body sizes in relation to normal and retarded fetal growth J.
W. WLADIMIROFF, M.D., PH.D.
C. A. BLOEMSMA, M.D.
H. C. S. WALLENBURG, M.D., PH.D. Rotterdam, ThP Netherlands Data on consecutive ultrasonic measurements .of fetal biparietal diameter (B.P.D.) and fetal chest area in 303 normal and 84 small-for-dates fetuses are presented. Duration of pregnancy varied from 24 to 41 weeks. A normal curve of the fetal B.P.D., chest area, and head-to-chest ratio was constructed. At 24 weeks mean fetal B.P.D. was 6.29 em., mean fetal chest area was 24.9 sq. em., and mean head-to-chest ratio was 1.59. At 41 weeks the mean values were 9.81 em., 92.4 sq. em., and 1.05, respectively. In the group of
sma!!-fcr-dates fetuses, a norma! head-tcrchest ratio v1as almost aft11ays associated \Vith early onset of fetal growth retardation whereas in the majority of fetuses with increased head-to-chest ratios, growth retardation appeared to have started only in the third trimester of pregnancy. (AM. J. 0BSTET. GYNECOL. 131: 857, 1978.)
OVER THE YEARS several publications have appeared on the significance of ultrasonic measurement of fetal head size relative to fetal growth. 1- 4 Campbe!JZ described "low-profile" and "late-flattening" types of growth retardation, the first developing in the second trimester, the latter during the last trimester of pregnancy. The results of experiments on rats;;, 6 and rhesus monkeys'· Has well as pathologic findings in the human fetus" point to a relationship between the late-flattening type of fetal growth retardation and placental vascular From the Department of Obstetrics and Gynaecology, Academic Hospital Rotterdam-Dijkzigt. Supported by a Grant from "De Drie Lichten" Foundation, Hilversum, The Netherlands. Reaivrd for publiration June 6, 1977. Rei'isedjanuary 6, !978. .4crt•pted February 10, 1978. Reprint requests: Dr.]. W. WlfJdimiroff, Department of Obstetrics and Gynaecology, Academic Hospital Rotterdam-Dijkzigt, Dr. Molewaterplein 40, RottPrdam-3002. The Netherlands.
)002-9378/78/08131~0857$00.40/0
©
1978 The C. V. l\fosby Co.
insufficiency. In these studies brain-to-body ratio was elevated, suggesting a brain-sparing effect. It is therefore not surprising that increasing attention is being paid to ultrasonic measurement of body size with respect to the detection of fetal growth retardation. In our present study we have attempted to establish fetal head and chest sizes in normal pregnancy from 24 weeks onward and to determine the significance of fetal head and chest sizes and head-to-chest relationship with respect to retarded growth rate.
Material and methods Our study included 470 patients. Duration of pregnancy varied from 24 to 41 weeks. Each patient was certain of the date of onset of her last menstrual period. Pregnancy was defined as normal when no antenatal complications occurred and when fetal birth weight fell between the 1Oth and 90th percentiles, according to tables presented by Kloosterman, 10 with corrections being made for maternal parity and fetal sex. This was the case in 303 patients. The remaining 167
857
858
Wladimiroff, Bloemsma, and Wallenburg
August 15, 147K
J. Obstet.
Am.
Gvnecol.
95 95
biparietal diameter (em)
2
ch.,st area (cm )
90
90 100.0
10.00 10 5
9.50
92.0
9,00
84.0
8.50
76.0
8.00
68.0
7.50
60.0
7.00
52.0
6.50
44,0
6.00
36.0
5.50
28.0
43
20.0 ""---,r---,r---r---r--r--r---,...--,...--,----, 23 25 27 29 31 33 35 37 39 41 43
gestational age (wks).
gestational age (wks).
5.00
23
25
27
29
31
33
35
10 5
37
39
41
Fig. 1. The fifth, lOth, 90th, and 95th percentiles of the normal curve for fetal B.P.D. (Fig. 1), fetal chest area (Fig. 2), and fetal head-to-chest ratio (Fig. 3) between 24 and 41 weeks' gestation.
pregnancies were complicated. In 84 of these 167 cases, fetal birth weight fell below the 1Oth percentile forgestational weight. 1n all patients fetal growth was assessed by serial abdominal palpation and measuremeilt of the distance between the upper rim of the pubic bone and the uterine fundus using a tape measure. When there was a negative or positive discrepancy in fundal height equiYalent to two weeks, or more of growth or any other abnormal antenatal finding, the patient was referred to the Ultrasound Department. Fetal head size was determined by means of ultrasonic measurement of the B.P.D. with a sound velocity of 1,600 M. per second. Ultrasonic measurement of the cross-sectional chest area was performed immediately caudal to the fetal heart pulsations with a sound velocity of 1540 M. per second." Consecutive measurements of fetal B.P.D. and chest area were performed once or several times in each patient. In case of more than one measurement, only the most recent values were included in the study.
Results Normal pregnancy (N = 303). Fetal B.P.D. and che~t area measurements were plotted against gestational age (Figs. l and 2). The mean B.P.D. and chest area varied from 6.29 em. and 24.9 sq. em., respectively, at 24 weeks to 9.8 em. and 92.4 sq. em. at 41 weeks
Fig. 2. See legend to Fig. I. head-to-chest-ratio 2.00 1.80
1.60 1.40
95
1.20
90
10 5
0.80 0.60
0.40 0.20
23
25
27
29
31 gestational age (wk•).
Fig. 3. See legend to Fig. I.
of gestation. The B.P.D. squared (or head area) instead of the B.P.D. was used for calculation of the head·tQchest ratio. 11 Fig. 3 gives the head-to-chest ratio in relation to gestational age. Mean and standard deviation values and mean weekly growth rates of fetal B.P.D. are given in Table I. The weekly growth rate of fetal chest area and the head-to-chest ratio as calculated from the 50th per centile appeared to be linear and
Volumt· 131 ~umber
Ultrasonic assessment of fetal head and body sizes
head-to-chest ratio
head-to-chest rotio
2.00
l
2.0~
..
1.80~
~ :v~:
1.80~
~-·::.
1.60j
~
''"
..
~95
'·""' 1.20
"
-----=:::::
1.00 0.80
B.P.D. ;;.5% n ~ 29
0.60
birth weight 5-10'"/o ~ X <5% ~.
0,40
859
H
90
10 5
:·~:i
~:. =·~95
l,
1.20
~ ~:. -~
••
•
•
1.00
90 10
5
B.P.D. <5% n = 34
0.80
Birth weight 5-10% <5%
=. =.
0.60 0.40
0.20
•
0.20
I 23
25
27
29
31
33
35
37
39
41
43
23
27
25
I
I
I
I
I
29
31
33
35
37
gestational age ( wks)
'
39
I
I
41
43
gestational age (wks)
Fig. 4. Head-to-chest ratios in relation to the normal curve in 29 small-for-dates fetuses with normal B.P.D. and small chest area (Group !II. Table I!).
Fig. 5. Head-to-chest ratios in relation to the normal curve in 34 small-for-dates fetuses with small B.P.D. and chest area (Group IV, Table !!).
were 3.82 sq. em. and -0.028, respectively. Small-for-dates fetuses (N = 84). Table II shows the relationship between B.P.D .. chest area, and chest ratio in the 84 small-for-dates fetuses. In Groups I and II head-to-chest ratio was within the normal range. In Group III head-to-chest ratio often was increased (Fig. i), whereas in Group IV the ratio often was within normal limits (Fig. 5). The mean B.P.D. in Group III (9.61 em.) was significantly larger (Student's t test) than that in Group IV (8.66 em.); mean birth weights were 2.:~40 and 2.285 grams, respectively. Our clinical and ultrasonic data revealed that a normal head-to-chest ratio was nearly always associated with early onset of fetal growth retardation, i.e., between 21 and 30 weeks (mode, 25 weeks). In the majority of cases with an increased ratio, fetal growth retardation was observed first between 29 and 34 weeks (mode, 32 weeks). In Group I growth retardation either was associated with an otherwise uncomplicated pregnancy or could be attlibuted to placental insufficiency. In Groups I II and IV there appeared to be no relationship between head-to-chest ratio and the nature of the complication. The significance of ultrasonic measurement of fetal B.P.D. and chest area with respect to the pickup rate of fetal growth reta.rdation is demonstrated in Table III. When birth weight was between fifth and lOth percentiles, fetal B.P.D. and chest area were below the normal range in 34 and 66 per cent of the cases, respectively. The percentages were 54 and 86, respectively, when birth ·weight was belovv the fifth percentile.
Table I. Mean value (X\ standard deviation (S.D.), and mean weekly growth rate (d) for fetal B.P.D., as calculated from the 50th percentile between 24 and 41 weeks' gestation in normal pregnancy B.P.D.
Chest area
(em.)
(sq. em.)
Gestationalage(wk.)
X
21 25 26 27 2:-l 29
6.29 6.78 7.15 7 23 7.62 7.84
""
u
l.i
J"
O.l'"t
31 32 33 34 3.'> 36 37 3H 39 40 41
8.40 8.58 8.77 9.03 9.14 9.34 9.49 9.51 9.74 9.59 9.81
1
S.D.
X
0.23 0.36 0.24 0.36 0.22 0.27
24.9 31.6 36.2 38.0 41.1 45.4
I
Head-tochest ratio
S.D.
X
0.79 3.54 3.85 3.68 4.87 4.25
1.59 1.48 1.43 L38 1.48 1.36
{\C)/\ \}.~\}
r::n A :.J\J.'-1:
"1:.UJ
11.:.1.:) ""
0.21 0.23 0.32 0.21 0.26 0.18 0.28 0.24 0.12 0.27 0.17
51.5 57.6 56.8 62.1 67.6 72.0 74.9 77.4 85.7 89.4 92.4
4.63 3.97 4.97 6.48 7.52 7.06 7.23 7.66 8.25 4.17 6.99
1.38 1.28 1.36 1.32 1.25 1.22 1.21 1.18
A CQ
1.12
1.03 1.05
~
S.D.
B.P.D. (rm.)
0.09 0.23 0.16 0.12 0.16 0.11
0.43 0.37 0.33 0.29 0.26
1\ 1 q " . 1 ~J
" •..:.:J
I
0.15 0. I 0 0. 15 0.11 0.15 0.12 0.10 0.10 0.10 0.07 0.10
n.o•l
0.22 0.19 0.18 O.lli 0.15
0.13 () 13 0.12 0.11 0.10
O.lO
Comment Previous assessment ot the accuracv of B.P.D. and chest area measurement revealed a standard deviation of ±0.07 em. and ±0.84 sq. em., respecti"
i
860 Wladimiroff, Bloemsma, and Wallenburg Am.
J.
August 1:>, I \l7R Obstet. Gvnecol.
Table II. Relationship between fetal B.P.D., chest area, and head-to-chest ratio in the 84 small-for-dates fetuses, and the normal range (Figs. 1 to 3) Group (N) B.P.D. Chest area Head-to-chest ratio
I (19) Between fifth and 95th percentiles Between fifth and 95th percentiles Between fifth and 95th percentiles
II (2) Below fifth percentile Between fifth and 95th percentiles Between fifth and 95th percentiles
III (29) Between fifth and 95th percentiles Below fifth percentile Partly between fifth and 95th percentiles (N 7); partly above 95th percentile (N = 22)
Table III. The significance of fetal B.P.D. and chest area measurement in the detection of the small-for-dates infant Birth weight(%)
B.P.D. (em.)
Chest area (sq. em.)
5-10
16 (34%)
31 (66%)
20 (54%)
32 (86%)
(N ""47)
<5 (N = 37)
The growth rate of the chest area is linear, as opposed to that of the B.P.D., which at term slows down to about a fourth of the growth rate in the 25th week of pregnancy. Two factors are of importance for postpartum development of the undersized fetus: the cause of growth retardation and the moment at which growth retardation sets in. Growth retardation in the first half of the second trimester of pregnancy usually is the result of viral infections and genetic abnormalities leading to an over-all reduction in number of cells, including neuroblast proliferation 12 ; head and chest are affected in a similar way, head-to-chest ratio will therefore remain normal. In our study only one fetus with a normal head-to-chest ratio was anomalous (Potter's syndrome).
IV (34) Below fifth percentile Below fifth percentile Partly between fifth and 95th percentiles (N 23); partly above 95th percentile (N = 11)
Growth retardation in the last trimester of pregnancy usually is associated with reduced placental blood flow and increased head-to-chest ratio.~~" indicating a brain-sparing effect. From our data it appears that in several cases of placental insufficiency head-to-chest ratio was normal. In these instances clinical data indicate that impairment of placental function could well have started before the last trimester of pregnancy. On the other hand, in a considerable number of cases no apparent reason for the early or late slowdown in fetal growth could be found. Fancourt and colleagues 1a performed a followup study of small-for-dates full-term infants whose intrauterine growth was followed by ultrasonic cephalometry. The infants were examined at a mean age of 4 years. They found that a prolonged slow growth in utero seems to be followed by slow growth and development post partum. From Table III it appears that the chest area is a more sensitive parameter for detection of the growthretarded infant when compared with the fetal B.P.D. It can be concluded that head-to-chest ratios are helpful in determining the type and severity of intrauterine growth retardation. Measurement of chest area, as described in this paper, gives useful information indirectly about liver size. 14
REFERENCES I. Campbell, S., and Newman, G. B.: Growth of the fetal 2. 3. 4. 5. 6. 7.
biparietal diameter during normal pregnancy, Br. ]. Obstet. Gynaecol. 78: 513, 1971. Campbell. S.: Fetal growth, Clin. Obstet. Gynecol. 1: 41, 1974. Queenan,]. T., Kubarich, S. F., Cook, L. N., et al.: Diagnostic ultrasound for detection of intrauterine growth retardation, AM. J. 0BSTET. GYNECOL. 124: 865, 1976. Whetham, J. C. G., Muggah, H., and Davidson, S.: Assessment of intrauterine growth retardation by diagnostic ultrasound, AM.j. OssTET. GYNECOL. 125: .~77. 1976. Wigglesworth, J S.: Experimental growth retardation in the foetal rat, J. Pathol. Bacteriol. 88: 1, 1964. Winick, M.: Cellular changes during placental and fetal growth, AM. J. 0BS1ET. GYNECOL. 109: 166, 1971. Hill, D. E., Myers, R. E., Holt, A. B., et aL: Fetal growth retardation produced by experimental placental insufficiency in the rhesus monkey. II. Chemical composition of the brain, liver, muscle and carcass, Bioi. Neonate 19: 68, 1971.
8. Hill, D. E.: Experimental growth retardation in rhesus monkeys, in Elliot, K., and Knight, J.. editors: Size at Birth, North Holland, 1974, Elsevier. Excerpta Medica. p. 275. 9. Gruenwald, P.: Chronic fetal distress and placental insufficiency, Bioi. Neonate 5: 215, 1963. 10. Kloosterman, G. J.: On intrauterine growth. Int. J. Gynaecol. Obstet. 8: 895, 1970. 11. Wladimiroff, J. W., Bloemsma, C. A., and Wallen burg, H. C. S.: Ultrasonic assessment of fetal growth, Acta Obstet. Gynecol. Scan d. 56: 37, 1977. 12. Dobbing,]., and Sands,].: Timing of neuroblast multiplication in developing human brain. Nature 226: 639. 1970. 13. Fancourt, R., Campbell, S., Harvey, D., et aL: Follow-up study of small-for-dates babies: Br. Med. J. 1: 1435, 1976. 14. Wladimiroff, J. W., and Sekeris, A.: Ultrasonic assessment of liver size in the newborn, J. Clin. Ultrasound 5: 316, 1977.
Ultrasonic assessment of fetal head and body sizes in relation to normal and retarded fetal growth J.
W. WLADIMIROFF, M.D., PH.D.
C. A. BLOEMSMA, M.D.
H. C. S. WALLENBURG, M.D., PH.D. Rotterdam, ThP Netherlands Data on consecutive ultrasonic measurements .of fetal biparietal diameter (B.P.D.) and fetal chest area in 303 normal and 84 small-for-dates fetuses are presented. Duration of pregnancy varied from 24 to 41 weeks. A normal curve of the fetal B.P.D., chest area, and head-to-chest ratio was constructed. At 24 weeks mean fetal B.P.D. was 6.29 em., mean fetal chest area was 24.9 sq. em., and mean head-to-chest ratio was 1.59. At 41 weeks the mean values were 9.81 em., 92.4 sq. em., and 1.05, respectively. In the group of
sma!!-fcr-dates fetuses, a norma! head-tcrchest ratio v1as almost aft11ays associated \Vith early onset of fetal growth retardation whereas in the majority of fetuses with increased head-to-chest ratios, growth retardation appeared to have started only in the third trimester of pregnancy. (AM. J. 0BSTET. GYNECOL. 131: 857, 1978.)
OVER THE YEARS several publications have appeared on the significance of ultrasonic measurement of fetal head size relative to fetal growth. 1- 4 Campbe!JZ described "low-profile" and "late-flattening" types of growth retardation, the first developing in the second trimester, the latter during the last trimester of pregnancy. The results of experiments on rats;;, 6 and rhesus monkeys'· Has well as pathologic findings in the human fetus" point to a relationship between the late-flattening type of fetal growth retardation and placental vascular From the Department of Obstetrics and Gynaecology, Academic Hospital Rotterdam-Dijkzigt. Supported by a Grant from "De Drie Lichten" Foundation, Hilversum, The Netherlands. Reaivrd for publiration June 6, 1977. Rei'isedjanuary 6, !978. .4crt•pted February 10, 1978. Reprint requests: Dr.]. W. WlfJdimiroff, Department of Obstetrics and Gynaecology, Academic Hospital Rotterdam-Dijkzigt, Dr. Molewaterplein 40, RottPrdam-3002. The Netherlands.
)002-9378/78/08131~0857$00.40/0
©
1978 The C. V. l\fosby Co.
insufficiency. In these studies brain-to-body ratio was elevated, suggesting a brain-sparing effect. It is therefore not surprising that increasing attention is being paid to ultrasonic measurement of body size with respect to the detection of fetal growth retardation. In our present study we have attempted to establish fetal head and chest sizes in normal pregnancy from 24 weeks onward and to determine the significance of fetal head and chest sizes and head-to-chest relationship with respect to retarded growth rate.
Material and methods Our study included 470 patients. Duration of pregnancy varied from 24 to 41 weeks. Each patient was certain of the date of onset of her last menstrual period. Pregnancy was defined as normal when no antenatal complications occurred and when fetal birth weight fell between the 1Oth and 90th percentiles, according to tables presented by Kloosterman, 10 with corrections being made for maternal parity and fetal sex. This was the case in 303 patients. The remaining 167
857
858
Wladimiroff, Bloemsma, and Wallenburg
August 15, 147K
J. Obstet.
Am.
Gvnecol.
95 95
biparietal diameter (em)
2
ch.,st area (cm )
90
90 100.0
10.00 10 5
9.50
92.0
9,00
84.0
8.50
76.0
8.00
68.0
7.50
60.0
7.00
52.0
6.50
44,0
6.00
36.0
5.50
28.0
43
20.0 ""---,r---,r---r---r--r--r---,...--,...--,----, 23 25 27 29 31 33 35 37 39 41 43
gestational age (wks).
gestational age (wks).
5.00
23
25
27
29
31
33
35
10 5
37
39
41
Fig. 1. The fifth, lOth, 90th, and 95th percentiles of the normal curve for fetal B.P.D. (Fig. 1), fetal chest area (Fig. 2), and fetal head-to-chest ratio (Fig. 3) between 24 and 41 weeks' gestation.
pregnancies were complicated. In 84 of these 167 cases, fetal birth weight fell below the 1Oth percentile forgestational weight. 1n all patients fetal growth was assessed by serial abdominal palpation and measuremeilt of the distance between the upper rim of the pubic bone and the uterine fundus using a tape measure. When there was a negative or positive discrepancy in fundal height equiYalent to two weeks, or more of growth or any other abnormal antenatal finding, the patient was referred to the Ultrasound Department. Fetal head size was determined by means of ultrasonic measurement of the B.P.D. with a sound velocity of 1,600 M. per second. Ultrasonic measurement of the cross-sectional chest area was performed immediately caudal to the fetal heart pulsations with a sound velocity of 1540 M. per second." Consecutive measurements of fetal B.P.D. and chest area were performed once or several times in each patient. In case of more than one measurement, only the most recent values were included in the study.
Results Normal pregnancy (N = 303). Fetal B.P.D. and che~t area measurements were plotted against gestational age (Figs. l and 2). The mean B.P.D. and chest area varied from 6.29 em. and 24.9 sq. em., respectively, at 24 weeks to 9.8 em. and 92.4 sq. em. at 41 weeks
Fig. 2. See legend to Fig. I. head-to-chest-ratio 2.00 1.80
1.60 1.40
95
1.20
90
10 5
0.80 0.60
0.40 0.20
23
25
27
29
31 gestational age (wk•).
Fig. 3. See legend to Fig. I.
of gestation. The B.P.D. squared (or head area) instead of the B.P.D. was used for calculation of the head·tQchest ratio. 11 Fig. 3 gives the head-to-chest ratio in relation to gestational age. Mean and standard deviation values and mean weekly growth rates of fetal B.P.D. are given in Table I. The weekly growth rate of fetal chest area and the head-to-chest ratio as calculated from the 50th per centile appeared to be linear and
Volumt· 131 ~umber
Ultrasonic assessment of fetal head and body sizes
head-to-chest ratio
head-to-chest rotio
2.00
l
2.0~
..
1.80~
~ :v~:
1.80~
~-·::.
1.60j
~
''"
..
~95
'·""' 1.20
"
-----=:::::
1.00 0.80
B.P.D. ;;.5% n ~ 29
0.60
birth weight 5-10'"/o ~ X <5% ~.
0,40
859
H
90
10 5
:·~:i
~:. =·~95
l,
1.20
~ ~:. -~
••
•
•
1.00
90 10
5
B.P.D. <5% n = 34
0.80
Birth weight 5-10% <5%
=. =.
0.60 0.40
0.20
•
0.20
I 23
25
27
29
31
33
35
37
39
41
43
23
27
25
I
I
I
I
I
29
31
33
35
37
gestational age ( wks)
'
39
I
I
41
43
gestational age (wks)
Fig. 4. Head-to-chest ratios in relation to the normal curve in 29 small-for-dates fetuses with normal B.P.D. and small chest area (Group !II. Table I!).
Fig. 5. Head-to-chest ratios in relation to the normal curve in 34 small-for-dates fetuses with small B.P.D. and chest area (Group IV, Table !!).
were 3.82 sq. em. and -0.028, respectively. Small-for-dates fetuses (N = 84). Table II shows the relationship between B.P.D .. chest area, and chest ratio in the 84 small-for-dates fetuses. In Groups I and II head-to-chest ratio was within the normal range. In Group III head-to-chest ratio often was increased (Fig. i), whereas in Group IV the ratio often was within normal limits (Fig. 5). The mean B.P.D. in Group III (9.61 em.) was significantly larger (Student's t test) than that in Group IV (8.66 em.); mean birth weights were 2.:~40 and 2.285 grams, respectively. Our clinical and ultrasonic data revealed that a normal head-to-chest ratio was nearly always associated with early onset of fetal growth retardation, i.e., between 21 and 30 weeks (mode, 25 weeks). In the majority of cases with an increased ratio, fetal growth retardation was observed first between 29 and 34 weeks (mode, 32 weeks). In Group I growth retardation either was associated with an otherwise uncomplicated pregnancy or could be attlibuted to placental insufficiency. In Groups I II and IV there appeared to be no relationship between head-to-chest ratio and the nature of the complication. The significance of ultrasonic measurement of fetal B.P.D. and chest area with respect to the pickup rate of fetal growth reta.rdation is demonstrated in Table III. When birth weight was between fifth and lOth percentiles, fetal B.P.D. and chest area were below the normal range in 34 and 66 per cent of the cases, respectively. The percentages were 54 and 86, respectively, when birth ·weight was belovv the fifth percentile.
Table I. Mean value (X\ standard deviation (S.D.), and mean weekly growth rate (d) for fetal B.P.D., as calculated from the 50th percentile between 24 and 41 weeks' gestation in normal pregnancy B.P.D.
Chest area
(em.)
(sq. em.)
Gestationalage(wk.)
X
21 25 26 27 2:-l 29
6.29 6.78 7.15 7 23 7.62 7.84
""
u
l.i
J"
O.l'"t
31 32 33 34 3.'> 36 37 3H 39 40 41
8.40 8.58 8.77 9.03 9.14 9.34 9.49 9.51 9.74 9.59 9.81
1
S.D.
X
0.23 0.36 0.24 0.36 0.22 0.27
24.9 31.6 36.2 38.0 41.1 45.4
I
Head-tochest ratio
S.D.
X
0.79 3.54 3.85 3.68 4.87 4.25
1.59 1.48 1.43 L38 1.48 1.36
{\C)/\ \}.~\}
r::n A :.J\J.'-1:
"1:.UJ
11.:.1.:) ""
0.21 0.23 0.32 0.21 0.26 0.18 0.28 0.24 0.12 0.27 0.17
51.5 57.6 56.8 62.1 67.6 72.0 74.9 77.4 85.7 89.4 92.4
4.63 3.97 4.97 6.48 7.52 7.06 7.23 7.66 8.25 4.17 6.99
1.38 1.28 1.36 1.32 1.25 1.22 1.21 1.18
A CQ
1.12
1.03 1.05
~
S.D.
B.P.D. (rm.)
0.09 0.23 0.16 0.12 0.16 0.11
0.43 0.37 0.33 0.29 0.26
1\ 1 q " . 1 ~J
" •..:.:J
I
0.15 0. I 0 0. 15 0.11 0.15 0.12 0.10 0.10 0.10 0.07 0.10
n.o•l
0.22 0.19 0.18 O.lli 0.15
0.13 () 13 0.12 0.11 0.10
O.lO
Comment Previous assessment ot the accuracv of B.P.D. and chest area measurement revealed a standard deviation of ±0.07 em. and ±0.84 sq. em., respecti"
i
860 Wladimiroff, Bloemsma, and Wallenburg Am.
J.
August 1:>, I \l7R Obstet. Gvnecol.
Table II. Relationship between fetal B.P.D., chest area, and head-to-chest ratio in the 84 small-for-dates fetuses, and the normal range (Figs. 1 to 3) Group (N) B.P.D. Chest area Head-to-chest ratio
I (19) Between fifth and 95th percentiles Between fifth and 95th percentiles Between fifth and 95th percentiles
II (2) Below fifth percentile Between fifth and 95th percentiles Between fifth and 95th percentiles
III (29) Between fifth and 95th percentiles Below fifth percentile Partly between fifth and 95th percentiles (N 7); partly above 95th percentile (N = 22)
Table III. The significance of fetal B.P.D. and chest area measurement in the detection of the small-for-dates infant Birth weight(%)
B.P.D. (em.)
Chest area (sq. em.)
5-10
16 (34%)
31 (66%)
20 (54%)
32 (86%)
(N ""47)
<5 (N = 37)
The growth rate of the chest area is linear, as opposed to that of the B.P.D., which at term slows down to about a fourth of the growth rate in the 25th week of pregnancy. Two factors are of importance for postpartum development of the undersized fetus: the cause of growth retardation and the moment at which growth retardation sets in. Growth retardation in the first half of the second trimester of pregnancy usually is the result of viral infections and genetic abnormalities leading to an over-all reduction in number of cells, including neuroblast proliferation 12 ; head and chest are affected in a similar way, head-to-chest ratio will therefore remain normal. In our study only one fetus with a normal head-to-chest ratio was anomalous (Potter's syndrome).
IV (34) Below fifth percentile Below fifth percentile Partly between fifth and 95th percentiles (N 23); partly above 95th percentile (N = 11)
Growth retardation in the last trimester of pregnancy usually is associated with reduced placental blood flow and increased head-to-chest ratio.~~" indicating a brain-sparing effect. From our data it appears that in several cases of placental insufficiency head-to-chest ratio was normal. In these instances clinical data indicate that impairment of placental function could well have started before the last trimester of pregnancy. On the other hand, in a considerable number of cases no apparent reason for the early or late slowdown in fetal growth could be found. Fancourt and colleagues 1a performed a followup study of small-for-dates full-term infants whose intrauterine growth was followed by ultrasonic cephalometry. The infants were examined at a mean age of 4 years. They found that a prolonged slow growth in utero seems to be followed by slow growth and development post partum. From Table III it appears that the chest area is a more sensitive parameter for detection of the growthretarded infant when compared with the fetal B.P.D. It can be concluded that head-to-chest ratios are helpful in determining the type and severity of intrauterine growth retardation. Measurement of chest area, as described in this paper, gives useful information indirectly about liver size. 14
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