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OCR for page 118
Chapter IX
ANALYSIS OF THE STILLBIRTH DATA
9.1 The trait. The definition of a stillbirth
employed in this study is an infant who shows
no signs of life at birth, following a period of
gestation of at least 20 weeks. Any infant that
moves, makes respiratory attempts, or is born
with a beating heart is not in the strict sense
"stillborn." This definition, which is that em-
ployed in United States vital statistics, runs
counter to current Japanese usage, under which
infants who showed signs of life at birth but
never succeeded in establishing a pattern of
regular respiration are frequently reported as
stillborn. This usage was in part a matter of
convenience, since a stillbirth required com-
pleting only one official form, whereas a live-
birth dying an hour following delivery required
completing two. The subject of the ABCC's
usage of the term "stillbirth" was repeatedly
taken up at conferences with the midwives.
The frequency of stillbirths encountered in
our control material (both parents category 1)
was in Hiroshima 1.27 per cent of all births
(17,189 births) and in Nagasaki 1.31 per cent
(14,450 births). In comparison, in 1950 the
"official" stillbirth rate (stillbirths per 1,000
livebirths) was in Hiroshima prefecture 79.6
and in Nagasaki prefecture 87.7, or, expressed
as percentage of all births, 7.37 per cent and
8.07 per cent respectively (Public Health and
Welfare in Japan, 1950~. Official statistics for
other years are similar. There is apparent a
marked discrepancy between official statistics
and our own. There are at least five factors to
be taken into account in an evaluation of these
differences. Firstly, there is the matter of recis-
tration practices referred to above. Secondly,
the official stillbirth data are for stillbirths after
the third month of uterogestation, whereas by
and large our figures refer to events following
the fifth month of gestation. Thirdly, since the
official figures are for an entire prefecture, there
is the possibility of urban-rural differentials.
~8
This, however, works in the opposite direction
than the first two factors, since in 1950 the
stillbirth rate for all ski (cities) was 134.0 per
1,000 livebirths, whereas for all gun (villages
and rural areas) the rate was 70.4. Fourthly, the
official figures may include some induced termi-
nations, whereas these were excluded from our
own data. Lastly, those stillborn infants with
gross malformations were excluded from our
figures. The reasons for this exclusion were
given in Section 6.2.
When approximate allowance is made for
the exclusion from our figures of stillborn,
malformed infants, the stillbirth rates observed
in this study are quite similar to those currently
obtaining in many parts of the United States
(e.g., Michigan, 1950, 1.9 per cent). The possi-
bility that the ABCC program was failing to
obtain data on any substantial number of still-
births seems precluded by the efficiency of preg-
nancy registration (Sec. 2.1) and the system of
careful follow-up for all registered terminations.
9.2 The genetic artz~mer~t for radiation-ir;-
duced changes. Animal experimentation on
the genetic effects of irradiation indicates that
the largest group of induced mutations having
clear-cut effects detectable in the first generation
of offspring following exposure are the auto-
somal lethals. As detected in the first genera-
tion of offspring these mutations would consist
largely of the dominant lethals, although a few
recessive lethals would be recovered due to the
fortuitous combination in some individuals of
an induced lethal mutant with an allelic lethal
mutant of spontaneous origin. Presumably one
of the manifestations of the presence of these
mutant genes would be fetal death. Accordingly,
we might expect, as one of the changes sympto-
matic of irradiation-induced genetic damage, an
increase in the frequency with which infants
are stillborn as parental exposure increases.
9.3 Cor~comitc~nt ~ariatiorl knower to affect
OCR for page 119
Analysis of the Stillbirth Data
the stillbirth rate.-No one of the indicators
with which we have dealt or shall deal is more
complex with respect to concomitant variation
than the one presently under consideration. No
less than seven sources of concomitant variation
known to affect the stillbirth rate could, con-
ceivably, be influencing the data which we shall
analyze. These seven sources of extraneous vari-
ation are congenital syphilis, birth injury, ma-
ternal age, parity, nutrition, rate of reproduc-
tion, and paternal age.
Congenital syphilis has long been one of the
major causes of fetal mortality. In Hiroshima
and Nagasaki the frequency of positive serolo-
gies is from 5 to 7 per cent among post-parturi-
ent women. To assess the amount of infantile
mortality attributable to congenital syphilis
among the births described here would have
required an expenditure of time and energy
which, because of the limitations of personnel
119
by syphilitic stillborn infants (and we have no
evidence that it is not) then, because of the
known differential in maternal age among the
parental exposure cells, herein lies a possible
source of bias. The age distribution among the
exposure cells is such that this bias would tend
to inflate the stillbirth rate among those parents
less heavily exposed or not exposed at all. How-
ever, these potential effects would appear to be
quite small, of a magnitude which could safely
be ignored in this analysis.
A second major factor affecting infant sur-
vival (which it was not possible to control) is
the occurrence of an injury during parturition.
In the United States, it has been estimated that
birth injury accounts for no less than 13.6 per
cent of infantile mortality (Stander, 1941~.
Of the various types of injuries which may be
sustained during the passage of the infant
through the birth canal, by far the most common
TABLE 9.1 CONGENITAL SYPHILIS AMONG LIVING INFANTS BORN IN NAGASAKI IN 19 51
(Incidence and relation to maternal age [after Wright, S.w. et al., 19523)
Maternal age: years
Totals
Number of living infants6,673
Number of cases of congenital
syphilis 47
Incidence X 1,000 7
%2_ 11.160
1 5-19 2~24
181 1,691
4
22
and facilities, was not possible. However, a
small study was made in Nagasaki on infants
born in the year 1951 in an attempt to deter-
mine the incidence of congenital syphilis among
the infants being examined in connection with
the genetics program (Wright, S. W. et al.,
1952~. Initially it was planned that this study
would estimate the incidence of congenital
syphilis among living infants, stillbirths, and
neonatal deaths. Because of the formidable diffi-
culties posed in estimating the latter incidences
in the absence of an exhaustive post-mortem
program in Nagasaki, attention had to be fo-
cused on living infants alone. Two items of
interest here emerged from this study. Firstly,
some seven out of every thousand liveborn
infants were shown to have congenital syphilis
either by clinical, serologic, or roentgenologic
examination, or any combination thereof. Sec-
ondly, a gradual decline in the rate of trans-
mission with increasing maternal age was noted.
These latter data are reproduced in Tame 9.1.
If this same effect of maternal age is exhibited
17
10
DF= 5
25-29
2,435
16
6.5
30-34
1,456
35-39
735
5 4
3.4 5.4
P < 0.05
40 44
171
5.8
45-50
o
o
is intra-cranial injury with hemorrhage. It has
been reported that 40-80 per cent of infants
coming to autopsy will show evidence of this
form of birth injury (Stander, 1941~. In our
own data among 50 autopsied infants, se-
lected at random, 26 showed intra-cranial
hemorrhages ranging from moderate to severe
in degree. While the importance of birth injury
in infantile death cannot be gainsaid, it is di~-
cult to visualize circumstances which would lead
to a non-random distribution of birth injuries
among the parental exposure categories, and
this possibility will be ignored in the analysis.
A third major factor affecting infant survival
is maternal nutrition. The importance of this
variable is amply attested to by an extensive
literature. In the main, this literature is in agree-
ment in indicating that rather drastic changes
in maternal nutrition must occur before clearly
demonstrable changes in the stillbirth rate can
be shown (see, for example, Antonov, 1947,
and Smith, 1947~. There is no evidence that
during the course of this study the limitations
OCR for page 120
120
Genetic Effect of
imposed on maternal nutrition by economic
conditions prevailing in Japan reached the levels
necessary to produce measurable changes in the
stillbirth rate, or that (arguing again from the
rough classification of economic status presented
in Sec. 5.3) such differences in maternal nutri-
tion as existed were non-randomly distributed.
Among the variables affecting the stillbirth
rate previously enumerated, the effects of ma-
ternal age and parity are by far the most com-
plex and general in scope. These effects as
TABLE 9.2 THE EFFECT OF MATERNAL AGE AT FIXED PARITY
(The meaning of the symbols employed it
Atomic Comics Chapter IX
manifested in the present material are sum-
marized in Tables 9.2 and 9.3 and Figures 9.1
and 9.2. The data are presented and analyzed in
the same manner as age and parity effects with
respect to major congenital malformations (cf.
Sec. 8.4~. Again, a detailed discussion of the
findings will be deferred for a subsequent publi-
cation. There is a significant effect on stillbirth
frequency of both age and parity, with, in both
instances, an apparent increase in stillbirth fre-
quency at the extremes of the scale. This in
ON THE FREQUENCY OF STIT [BORN INFANTS
explained in Sec. 8.4.)
Total Normal Stillborn Per cent
births births infants stillborn AD
Parity 1
< 21 1,9121,882 30 1.57 .01995
21-25 8,6238,479 144 1.67 .05687
26-30 3,1923,125 67 2.10 .03101
31-35 614595 19 3.09 .02920
36-40 ............ 178} 189 17} 4.06 .01661
....... ... ... ......... ... ~
Total 14,538 14,270 268 .15364
X 5 = 14.046* IAD = 0.0768
PT = 0.2612
Parity 2
<21 ......................... 421 415 6 1.43 .01095
21-25 ......................... 6,639 -6,572 67 1.01 .00615
26-30 ......................... 6,354 6,294 60 0.94 .03259
31-35 ......................... 1,415 1,399 16 1.13 .00983
36-40 ......................... 366 360 6 1.64 .01460
41 + 47 46 1 2.13 .00336
~-
Total 15,24215,086 156 .07748
X25 = 3.174 IAD = 0.0387 PT = 0~2738
Parity 3
21-25 36} 2,224 23} 1.02 .03634
26-30 ......................... 5,799 5,729 70 1.21 .01513
31-35 ......................... 2,390 2,357 33 1.38 .02444
41 + . 66} 580 11} 1.86 .02703
Total 11,027 10,890 137 .10294
X23 ~ 3.153 IAD = 0.0515
PT = 0.1981
Parity 4
21-25 478}4766} 1.45 .02010
26-30 .........................2,8482,82820 070 .16468
31-35 .........................2,5212,48734 1.35 .07112
36-40 .........................75073614 1.87 .07286
41 + 84 83 1 1.19 .00060
Total 6,686 6,610 76 .32936
X24 = 9.770 Ion = 0.1647
PT = 0.12O1
OCR for page 121
Analysis of the Stillbirth Data
TABLE 9.2 Continued
Total Normal Stillborn Percent
births births infants stillborn AD
Parity 5
21-25 7876 2 2.56 .01723
26-30 991975 16 1.61 .03879
31-35 1,7561,737 19 1.08 .11020
36-40 837823 14 1.67 .04208
41-- 9795 2 2.06 .01211
Total3,7593,706 53 .22041
X24 = 3.~16 IAD = 0.1102
PT = 0.0675
Parity 6
26-30 262T 270 3) 1.46 .00158
31-35 956 943 13 1.36 .03585
36-40 794 785 9 1.13 .08678
41 + 141 135 6 4.26 .12421
Total 2,165 2,133 32 .24842
X23 = 8.208* IAD = 0.1242
PT = 0.0389
Parity 7 +
21-25 4) 58 2T 4.92 .02803
31-35 488 479 9 1.84 .05538
36-40 1,195 1,167 28 2.34 .02451
41 + 498 483 15 3.01 .05188
Total 2,242 2,187 55 .15980
X23 = 3.015 IAD = 0.0799
PT = 0.0403
All parities
< 21 2,374 2,337 37 1.56 .00507
21-25 18,045 17,801 244 1.35 .01032
26-30 ; 19,503 19,265 238 1.22 .04472
31-35 10,140 9,997 143 1.41 .00189
36-40 4,645 4,556 89 1.92 .03153
41 + 952 926 26 2.73 .01659
Total 55,659 54,882 777
XO5 = 26.547*. IAD, (forage) = 0.0761
crease at the lower end of the scale is more
definite with respect to parity than with respect
to age.
One of the more exhaustive previous studies
of this relationship of maternal age and parity
to infant survival is that of Yerushalmy (1945),
who found that (1) "the lowest rates do not
occur in one particular age group irrespective
of parity. There is a consistent shifting of the
minimum rate to the older ages with increasing
parity." (2) "When the stillbirth rates by age
of mother are compared for the different parity
groups the increase in the rate is not propor-
tionate for the various age groups. The increase
is very much higher for the younger age of
mother groups than for the older." The present
data appear to agree with the first of these two
conclusions, but of themselves would scarcely
permit drawing the second conclusion- this
may be in part a matter of the numbers involved.
From the standpoint of controlling extraneous
variation, these findings, taken in conjunction
with our own, imply that the only really ade-
quate control is one which takes into account
not only maternal age but also parity. Among
the Japanese data, to effect an adequate control
would require recognizing approximately 25
parity-specific age intervals (five intervals for
parity, and five for age, or 25 in all). The data,
because of the already existing numerous ways
OCR for page 122
22
Genetic Efects of Atomic Bom bs Chapter IX
TABLE 9.3 THE EFFECT OF ~ATERNAL PARITY AT FIXED AGE ON THE FREQUENCY OF STILLBORN INFANTS
(The meaning Of the SYmbO1S emP1OYed iS eXP1ained in SeC. 8.4.)
MOther'S age: < 21
TOta1 NOrma1 Sti11bOrn Per Cent
birthS birthS infantS Sti11bOrn AD
1,912 1,882 30 1.57 .00551
421 415 6 1.43 .01542
41 40 1 2.44 .00991
TOta1 2,374 2,337 37 - .03084
X22 = 0.257 IAD = 0.0154 PT = 0.0427
MOther'S age: 21-25
1 8,623 8,479 144 1.67 .11384
2 6,639 6,572 67 1.01 .09460
3 2 211 2 188 23 1.04 .02865
. . . . . . . . . . .. . ...
4 478 472 6 1.26 .00193
5 78T 90 4 4.26 .01133
6+ 16F
TOta1 18,045 17,801 244 .25035
X24 19.969** IAD = 0.1252 PT = 0.3242
MOther'S age: 26-30
1 3 192 3 125 67 2.10 .11930
. . . . . . . . . . . . . . .
2 ............................. 6,354 6,294 60 .94 .07461
~5 799 5 729 70 1.21 .00326
, ............................. . .
4 ............................. 2,848 2,828 20 .70 .06276
S 991 975 16 1.61 .01662
. .. . .. . .. . .. . .. . . . . .. . . . . .. . .
6 262 259 3 1.15 .00083
71 57 55 2 3.51 .00555
T .
TOta1 19,503 19,265 238 - .28293
X26 = 34.577~: * IAD = 0.1415 PT = 0~3504
MOther'S age: 31-35
1 ............................. 614 595 19 3.09 .07335
2 ............................. 1,415 1,399 16 1.13 .02805
3 ............................. 2,390 2,357 33 1.38 .00500
4 2 521 2 487 34 1.35 .01101
. . . . . . . . . . . . . . . . . . . . . . .
5 ............................. 1,7561,73719 1.08 .04088
6 95694313 1.36 .00342
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 + 48847991.84 .01503
TOta1 10,1409,997143- .17674
X26 = 15.444* IAD = 0.0884 PT = 0.1822
MOther'S age: 36~0
1 178 171 7 3.93 .04112
2 366 360 6 1.64 .01160
. . . . .. . .. . . . .. . . . . . .. . . . .. . ..
~525514 112.10 .01077
~
4750736 141.87 .00435
. .. . . . .. . . . .. ... . . .. . .. .. . .. .
837823 141.67 .02334
5
6 794 785 9 1.13 .07118
7 + 1,195 1,167 28 2.34 .05846
........................ 4,645 4,556 89 - .22082
X245 _ 8.111 IAD = 0.1104 PT = 0.0835
OCR for page 123
A nalysis of the Stillbirth Data
TABLE 9.3 Continued
Mother's age: 41 +
123
Total Normal Stillborn Per cent
births births infants stillborn AD
19 18 1 5.26]
47 46 1 2.13 ~.06346
66 -66 - - ~
84 83 1 1.19 .05117
97 95 2 2.06 .02567
141 135 6 4.26 .08499
498 483 15 3.01 .05533
........................ 952 926 26 - .28062
X24 = 3.030 IAD = 0.1403 PT = 0.0171
All ages
1 ............................. 14,538 14,270 268 1.84 .08491
2 ............................. 15,242 15,086 156 1.02 .07411
3 ............................. 11,027 10,890 137 1.24 .02211
4 ............................. 6,686 6,610 76 1.14 .02263
5 ............................. 3,759 3,706 53 1.41 .00068
6 ............................. 2,165 2,133 32 1.48 .00231
7 + 2,242 2,187 55 2.45 .03094
Total 55,659 54,882 777
X26 = 59.978** IAD" (for parity)=0.1186
s.o
4.5
4.0
3.s
3.0
2.5
ST ILL BIRTHS
(PER CENT)
2.0
·.5- l
1 n.
. .
0.5
'. /
'5 20 25 30 35
MOTHER S AGE
PARITY
- 7.
6
__ _ s \ ~I
-- 4 \ / I
...... 3
J
/
. ~ 1 \ / .~/
40 45
FIGURE 9.1 The distribution of the frequency of stillborn infants by age of mother for specified parities.
OCR for page 124
124
4.5.
STI LLBIRTHS
(PER CENT)
4.0+
3.~
-
3.0
2.5
2.0
1.5
1 .0
0.5
1 2
FIGURE 9.2 The distribution of the frequency of
of classification, would not permit so elegant an
approach to the extraneous variation occasioned
by mother's age and parity. Accordingly, it
became a matter of judgment as to which of
these two factors was to be controlled. A de-
cision was reached to disregard age but to
recognize, for analytical purposes, five parity
classes, namely, parity 1, parities 2-3, 4-5, 6-7,
and 8 and higher.
9.4 The data.-Tables 9.4 and 9.5 present
the distribution and analysis of stillborn infants
by sex, city, and parental exposure without fur-
ther subdivision by parity. Inspection of Table
9.4 suggests a difference in the stillbirth rate
when the mother was not exposed as opposed
to when she was. From the analytical table
(9.5a) we note a significant effect of mother's
exposure but not of sex or father's exposure.
Attention is called to the fact that the sex-
mother's exposure interaction is not significant,
in contrast to expectation in view of the possi-
ble effect of exposure on the sex ratio described
in Chapter VII. With regard to the reality of
the effect of mother's exposure on the stillbirth
rate, it should be borne in mind that these data
Genetic Efecis of Atomic Bombs Chapter IX
MATERNAL AGE ,
\
36-40 1
~ ~ ~ - 31 - 35 1
....... - 26-3.0 1
- - - - 21-25 1
1
i
1
1
\ /\l ,,.''/
~ ,_~
. _ . _ · ,
. ·
. .
3 4 5 6
PARITY
7+
stillborn infants by parity for specified maternal ages.
are uncorrected for parity and the more heavily
exposed cells are biased in a way which would
increase the stillbirth rate in these cells. If in
the analysis of Table 9.4 we limit our attention
to those exposure cells in which both parents
were exposed, which would reduce the differ-
ences between cells with regard to parity, the
apparent effect of maternal exposure disappears
(see Table 9.5b). This observation is of con-
siderable importance in the interpretation of
these data since (a) maternal exposure con-
founds the effects of genetic and somatic damage
and hence a significant effect of maternal expo-
sure not reflected in paternal exposure might
well be a somatic rather than a genetic effect,
and (b) there is evidence which has been pre-
sented in Chapter V and elsewhere in this
report that the comparison of pregnancy ter-
minations occurring to exposure category 1 par-
ents with terminations occurring to parents in
any other exposure category is biased.
Let us now turn to a consideration of what
these data reveal when the sex of the infant is
ignored but terminations are classified with re-
spect to parity. Tables 9.6 and 9.7 present the
OCR for page 125
Analysis of the Stillbirth Data
TABLE 9.4 FREQUENCY OF STILLBIRTHS BY SEX, PARENTAL EXPOSURE
AND CITY
(Unrelated parents)
Male infants
Hiroshima
Fathers
v,
~ .
4J -
o
1234-5Total
En8,91976130920810,197
14 s1141052131
l P.0128.0131.0162.0096.0128
En2,7969241951214,036
2/ s3615S561
lop.0129.0162.0256.0413.0151
En1,108220266801,674
3] s2718137
tp.0244.0045.0301.0125.0221
En5651085256781
4-5/ s14 1 15
tp.0248 .0192-.0192
in13,3882,01382246516,688
I Total s19126198244
p.0143.0129.0231.0172.0146
Male infants
Nagasaki
Fathers
125
1234-5Total
rrn7,5271,108125738,833
1: s1102111133
tp.0146.0190.0080.0137.0151
En4,8092,0871401037,139
2] s77323 112
tp.0160.0153.0214 .0157
~En3551325013550
=~; 3gs 6 1 7
tp .0169 .0076 -.0127
En 276 56 18 15365
4-5gs 2 1 3
~ p .0072 .0179 .0082
En12,9673,38333320416,887
Total~s1955541255
tp.0150.0163.0120.0049.0151
OCR for page 126
126 Genetic Effects of Atomic Bombs Chapter IX
TABLE 9.4 Continued
-
Female infants
Hiroshima
,-- ~
Fathers
cat
o
by
Total:
, ~
1234-5Total
rn 8,1907202801839,373
1g s 104996128
(p .0127.0125.0321.0328.0137
rn 2,5128971861213,716
2\ s 46114364
(p .0183.0123.0215.0248.0172
in 1,060202248761,586
33 s 2132127
tp .0198.0149.0081.0132.0170
in 539915560745
5gs 61 29
l P .0111.0110-.0333.0121
in12,301 1,91076944015,420
is177 241512228
p.0144 .0126.0195.0273.0148
Female infants
Nagasaki
.
, -
Fathers
, ~
1 234-5Total
rn 6,923 1,040112648,139
14 s 80 17 97
tp .0116 .0163--.0119
En 4,430 2,016133736,652
24 s 57 4923111
p .0129 .0243.0150.0411.0167
En 382 1424321588
34s 9 3- 12
tp .0236 .0211 .0204
(n 276 \601713366
4-5gs 4 21 7
(p .0145 .0333.0588-.0191
En12,0113,25830517115,745
Totals s1507133227
tp.0125.0218.0098.0175.0144
OCR for page 127
Analysis of the Stillbirth Data
TABLE 9.5 CHI-SQUARE ANALYSIS OF THE FRE
QUENCY OF STILLBIRTHS BY SEX, PARENTAL
EXPOSURE, AND CITY
(Unrelated parents)
a. All exposure cells (4 X 4)
Source DF %3 P
Total 63 92.343 .01-.02
Interactions, first order
C M 3 .620 .80-.90
CF 3 10.626 .01-.02
CS 1 0.200 .50-.70
SM 3 1.565 .50-.70
SF 3 5.499 .10-.20
M F 9 5.548 .70-.80
Main effects
Cities (C)a
Mother's exposure 1...
Mother's exposure-2...
Mother's exposure 3...
Mother's exposure 4, 5.
Sum ............
0.069 .70-.80
1 0.001 .95-.98
1 0.393 .50-.70
1 0.140 .70-.80
4 0.603 .95-.98
Sex (S)&
Mother's exposure 1 1 0.725 .30-.50
Mother's exposure - 2 1 0.661 .30-.50
Mother's exposure 3 1 0.202 .50-.70
Mother's exposure- 4,5. 1 0.065 .70-.80
Sum ............
Mothers (M) ............
4 1.653 .70-.80
3 12.797 .001-.01
Fathers (F)a
Mother's exposure - 1 3 3.943 .20-.30
Mother's exposure- 2 3 6.769 .05-.10
Mother's exposure 3 3 4.192 .20-.30
Mother's exposure 4,5. 3 0.187 .95-.98
Sum 12 15.091
.20-.30
b. Excluding parents in category 1 (3 X 3)
Total ...............
Interactions, first order
CM ...............
CF ..............
CS ..........
SM ........
SF ........
MF ..........
Main effects
.S~sr {.S)
35 14.186 .50-.70
2 2.001 .30-.50
2 4.121 .10-.20
1 5.737 .01-.02
2 2.083 .30-.50
2 4.825 .05-.10
4 0.781 .90-.95
_ ~_, 1 1.884
Cities (C) 1 1.150
Mothers (M) 2 2.816
Fathers (F) 2 0.388
a Adjusted for mothers
127
.10-.20
.20-.30
.20-.30
.80-.9n
OCR for page 128
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OCR for page 129
Analysis of the Stillbirth Data
distribution and analysis of stillborn infants
by city and parental exposure with further sub-
division by parity. It should be noted that, as
expected, there are significant differences in the
stillbirth rate among different parities. From
Table 9.7 we further note that when all ex-
posure cells are considered with reference to
TABLE 9.7 CHI-SQUARE ANALYSIS OF THE
FREQUENCY OF STILLBIRTHS BY PARENTAL
EXPOSURE, CITY, AND PARITY
(Unrelated parents)
Total .................
Interactions, first order
CM ................
CF .................
CP .................
ME .................
PM .................
PF .................
Main effects
Parity (P) ..........
City (C)'t ...........
Mothers (M) n
Parity Class 1......
Class 2......
Class 3......
Class 4......
Class 5......
DF X2
1S9 221.950
3
4
9
12
12
All classes 15
Fathers (F)a
Parity Class 1 3
Class 2 3
Class 3 3
Class 4 3
Class 5 3
All classes 15
a Adjusted for parity.
0.620
10.626
8.925
5.548
9.060
16.085
too 1-.0
.80-.90
.01-.02
.05-.10
.70-.80
.50-.70
.10-.20
53 599 < .001
8.965 .10-.20
3 4.879
3 7.537
3 4.008
3 4.269
3 2.003
22.696
21.79
1.865
0.518
3.521
1.117
28.770
.10-.20
.05-.10
.20-.30
.20-.30
.50-.70
.05-.10
< .001
.50-.70
.90-.95
.30-.50
.70-.80
.o 1-.02
parity, there is no effect of city or of maternal
exposure. However, an effect of paternal ex-
posure significant at the 5 per cent level now
appears. Inexplicably this latter effect seems to
be largely, if not entirely, attributable to those
fathers whose infants were firstborn. The fre-
quency of stillbirths among firstborn infants
by city and paternal exposure is presented in
Table 9.8. The data suggest a regular increase in
129
stillbirth frequencies with increasing paternal
exposure. To the end of determining whether
this apparent effect was explicable in terms of
the residual variation in maternal age not re-
moved by the parity classification, Table 9.9 was
prepared. An examination of this table reveals
a number of points of interest. Of the five age
groups investigated, the stillbirth rate increases
with paternal exposure in three and decreases
in two. In one of the three age groups (21-25)
the increase with paternal exposure primarily
TABLE 9.8 THE FREQUENCY OF STILLBIRTHS AMONG
FIRSTBORN INFANTS BY CITY AND PATERNAL
EXPOSURE
(Unrelated parents)
'1{S
En
2lP
~rn
=: As
~UP
rn
4-54~s
Cn
Total~s
City
Hiroshima Nagasaki
8,1625,937
15989
.0195.0150
8031,125
1834
.0224.0302
344113
132
.0378.0177
21352
1.11
.0516.0192
9,5227,227
201126
.0211.0174
Total
14,099
248
.0176
1,928
52
.0270
457
15
.0328
265
12
.0453
16,749
327
.0195
reflects a "1" vs. "non-1" difference. In sub-
stance, then, when maternal age as well as parity
is taken into account, there emerges no clearly
consistent relationship between paternal ex-
posure and the stillbirth rate.
9.5 Summary. Analysis of the stillbirth
data, taking into account differences between
exposure cells in the parity distributions, fails
to reveal significant differences between cities
or consistent significant effects of parental ex-
posure. The deviations from expectation ob-
served are so small and inconsistent that they
can scarcely be labeled as favoring or not favor-
ing genetic hypothesis.
OCR for page 130
130 Genetic Effects of Atomic Bombs Chapter IX
TABLE 9.9 THE FREQUENCY OF STILLBIRTHS AMONG FIRSTBORN INFANTS BY PATERNAL EXPOSURE AND
MATERNAL AGE
(Unrelated parents)
Fathers X22
Maternal ,
age 1234-5Total
J n 1,77235678292,23S]
<20 s 2981 38 ~1.055
ip .0164.0225.0128-.0170J
fn 8,5051,0312471419,924]
21-25> s 1382673174 ~5.908
UP .0162.0252.0283.0213.0175]
On 3,10037284563,612]
26-30/ s 6385480 ~11.962~*
up .0203.0215.0595.0714.0221 J
On 5641092926728]
31-35]s 137-121 ~5.768
up .0230.0642-.0385.0288 J
On 144511611222 ~
36-404 s 431412 ~11.047**
up .0278.0588.0625.3636.0541 ~
(n 1493228]
41 +] s 1-1 2 ~-
up .0714 .3333 .0714]
En14,099 1,928 457 265 16,749]
Total~s248 52 15 12 327
lP.0176 .0270 .0328 .0453 .0195 J
t Classes 3 and 4-5 are pooled.
Representative terms from entire chapter:
stillbirth rate
