1) Faculty of Nursing, Hiroshima International University
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
Original Article
Pelvic shape of contemporary young women: Related factors and impact on daily life
Haruko Shinkawa1), Yoko Takahata1)
Abstract Being safe and simple, external pelvimetry is also known for its usefulness in current developments in medical technologies. However, its standard measurement values have been used for more than 40 years, since the 1970s. This study therefore aimed to provide for a better understanding of changes in its standard measurement values by external pelvimetry and how pelvic shape is related to genetic factors, dieting for weight loss, and exercise experience. In addition, this study aimed to elucidate the relationship between pelvic size and balance, the daily discomforts frequently reported by women in early maturity, and to provide data leading to improved care that can contribute to a higher quality of life among women. Our results showed that contemporary women in early maturity have significant development in the intertrochanteric diameter of the pelvis, but no major change in other diameter lines. Development of the intertrochanteric diameter was associated with a higher intertrochanteric diameter-to-external conjugate ratio, but overall, no significant change was noted in pelvic balance. Pelvic size and balance were only slightly influenced by physique at birth and genetic factors, however current body fat percentage was of significant relevance. Of women with discomfort in daily life, those who had leg swelling, stiff neck, urinary incontinence, or abdominal bloating had larger pelvises, especially in the transverse direction, than women who did not have these symptoms. These findings revealed that in women with pelvic pain and fatigability, only the external conjugate is enlarged.
Key words: Discomforts, External pelvimetry, Pelvic balance, Pelvic size, Young women
原 著
現代の成熟期早期の女性の骨盤の形状と
その関連因子,日常生活への影響
新川 治子 1), 髙畑 陽子 1)
要 旨 骨盤外計測法は安全で簡便であることから , 医療技術の進歩した現在においてもその有用性が知られ
ているが ,標準値は 40 年以上変わっていない。そこで本研究は骨盤外計測器を用いて ,現代の成熟期早
期女性の各骨盤径線の変化 , 遺伝的因子や減量,運動の経験と骨盤の形状との関係 , 日常的な不快症状
との関係を明らかにすることを目的とした。結果 , 転子間径に有意な発達がみられるが , その他の径線
に大きな変化はなかった . また , 転子間径 / 外結合線比は拡大したが , 総合的には骨盤のバランスに著
しい変化は認められなかった . 骨盤の発育に出生時体格や遺伝的因子の影響は少なく , 現在の体脂肪率
が有意に関連している . 日常生活上の不快症状のうち下肢のむくみや肩こり , 尿失禁 , 腹部膨満感があ
る女性は , これらの症状のない女性よりも骨盤が大きく , 特に横方向が大きかった . 骨盤痛や易疲労感
のある者は外結合線のみが大きいことが明らかとなった .
キーワード:不快症状 ,骨盤外計測 ,骨盤のバランス ,骨盤の大きさ ,成熟期早期女性
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Pelvic shape of contemporary young women: Related factors and impact on daily life
Introduction The human pelvis is composed of the coxal
bone, sacrum, and coccyx, with multiple ligaments
that maintain stability. Pelvic development was
extensively researched from the 1970s to the
1990s. Results showed that in women, the pelvis
begins significant growth from the year preceding
menarche, as with height and the long bones, and
continues to grow for at least one or two years after
growth of the long bones has stopped (Araki, et al.,
1985). In terms of pelvic balance, a girl’s pelvis
develops properly in anteroposterior diameter from
age 6 to approximately age 10 and then develops its
transverse diameter. The anteroposterior diameter
is believed to also develop from late adolescence
to early maturity; age 20 to 25. (Araki, et al., 1985;
Onuma, 1977).
Bone growth is controlled by nutritional and
hormonal factors, and bone stress. The impact of
nutrition on bone growth in Japanese was made
clear in the years following World War II; as
nutrition improved so did Japanese physiques (Araki,
et al., 1980; Araki, et al., 1985). During puberty,
growth hormones and thyroxin cause dramatic
bone growth by acting on epiphyseal plates.
Estrogen, testosterone, and other sex hormones also
stimulate osteoblasts to build bones. As a result, the
epiphyseal plates become thinner and ossified, and
bone growth stops. When a force is applied to the
bone, bone minerals create a minute electric field
which attract osteoblasts. This means that bones are
thicker when a strong external force is applied but
become thin and brittle when external force is not
continuously applied (Martini, et al., 2000). These
demonstrate the essential factors that are crucial in
maintaining bone thickness.
While many countries have become concerned
with increased rates of obesity, Japan has long
faced the issue of young women who are too thin
(Sugawara, et al., 2009). According to the 2010
National Health and Nutrition Examination Survey
(Ministry of Health, Labour, and Welfare, 2013),
22% of women in their 20s are underweight, which
is markedly higher than other female age groups
or in men. It has been pointed out that the context
for this includes the trend of associating thinness
with beauty and related excessive dieting to lose
weight. Weight loss causes fat reduction that lowers
estrogen production and can cause amenorrhea.
Therefore, 48% of secondary amenorrhea cases
were reported to be anorexia nervosa (Sakakibara,
2011). Meanwhile, birth weight among newborns
has dropped significantly, peaking at 3200g in 1975
and dropping to 3002g in 2013, with an ongoing
increase in newborns who are small for their
gestational age. The increase in females dieting for
weight loss (hereafter, dieting), and for a longer
period of time, has been related to an increase in low
weight newborns.
Females who have dieted during the pelvic
development period have therefore been presumed to
have less estrogen secretion because of the reduction
in body fat, causing delayed bone ossification due
to delayed or arrested menarche. Poor nutrition,
in turn, has been surmised to cause inadequate
bone development, leading to a small pelvis or to a
pelvis that has a long anteroposterior diameter. In
modern society where lifestyles have become more
sedentary, pelvis development may be positively
affected by exercise such as experienced in junior
high and high school club and sports activities.
Despite these changes in women’s health issues and
lifestyles, very little research has been conducted
on pelvic shape in healthy women in early maturity
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
since the beginning of this century. Also, standard
pelvic measurement values (Nakanishi, 2001) have
not been updated since the 1970’s.
Accordingly, this study aimed to use external
pelvimetry, which was often used in the 1970s,
to measure the pelvis and better understand the
mechanisms of the changes in the length of, and
balance between, the diameter lines from the
standard measurement values, which have been
used for more than 40 years. Also, the relationships
between pelvic shape and genetic factors, as well as
to dieting and exercise that take place from puberty
to early maturity were investigated. In addition, this
study aimed to better understand the relationship
between pelvic size and balance, and the daily
discomfort frequently reported by women in early
maturity and to provide data leading to improved
care that would contribute to a higher quality of life
among women.
Research methods1. Participants
Participants were women aged 18 to 23 who were
attending university in Hiroshima Prefecture, and
recruited through posters displayed throughout the
campus. Of 163 respondents, 146 were included
in the study analysis; excluding those whose
questionnaires were incomplete.
2. Measurement tools
1) External pelvimetry
Narrow pelvis and cephalopelvic disproportion
(CPD) are diagnosed using radiography or magnetic
resonance imaging (MRI), which are able to directly
measure the size of the pelvic cavity. However,
performing MRI and radiography examinations
on healthy women have limitations in terms of
cost and safety. In this regard, external pelvimetry
offers a safe, simple, and noninvasive measurement
of bone length obtained by measuring the length
between two points from the skin surface. Though
different from the measured values on radiography
or MRI, the diameter lines, as determined by
external pelvimetry, were strongly and significantly
correlated with pelvimetric sites on radiography as
follows: the interspinal and transverse diameters of
the area of the pelvic inlet (r = .720), the external
conjugate and obstetric conjugatediameter (r =
.730), and the lateral conjugate and anteroposterior
diameter of the midpelvis (r = .733; Masuzaki, et
al., 1991).
This survey therefore measured external
pelvimetry by using the Martin pelvimeter. Figure 1
shows the measurement sites; the external conjugate
diameter, intercristal diameter, interspinous
diameter, intertrochanteric diameter, and external
oblique diameter. To improve reliability, precise
measurements were taken by researchers who were
midwives, and confirmed by pretest. Measurements
were obtained over one layer of thin clothing.
The intertrochanteric diameter-to-external
conjugate ratio, which served as the reference for
balance between the transverse and anteroposterior
diameters, was established to better understand
balance. The difference between the intercristal
and interspinal diameters, strongly associated with
platypelloid pelvises, was also investigated. A
principal component analysis established a pelvic
score indicative of the pelvic size. The pelvic score
was abridged into one component, with a cumulative
load of 58.2% and eigenvalue ranging from .629 to
.846.
Figure 1. External pelvimetry (quoted from Nakanishi, M. (2001))
① external conjugate diameter ④ intertrochanteric diameter② intercristal diameter ⑥ external oblique diameter③ interspinous diameter
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Pelvic shape of contemporary young women: Related factors and impact on daily life
2) Measurement of physique
Physique was determined by measuring height
and weight to calculate body mass index (BMI).
Body fat percentage (HBF-306-W body fat scale,
Omron) was measured by bioelectrical impedance.
Errors in measuring body fat percentage were
minimized by avoiding times immediately after
intense exercise and delaying measurement
approximately 1 to 2 hours after eating.
3) Basic information, lifestyle, and discomfort
Data were collected by questionnaire for
discomfort and for whether or not participants had
dieting experiences since junior high school. For
discomfort, respondents were asked if they had
experienced any of the 17 symptoms of discomfort
identified by Shinkawa (2009) over the previous
week. Participant physiques at birth and one month
after birth were assessed by obtaining copies
of health records from the Maternal and Child
Health Handbook. Birth mother physiques (for
nulligravidae) after giving birth were also assessed
by data provided by the Handbook.
3. Methods of analysis
Analysis relied on IBM SPSS Statistics 19.0.
Nakanishi’s (2001) pelvic diameters, widely used
as the standard measurement values in the perinatal
period, were used to compare our measurement
results by performing the test of population mean
with 95% confidence. The relationships between the
pelvic diameter lines, intertrochanteric diameter-
to-external conjugate ratio, the difference between
the intercristal and interspinal diameters, the pelvic
score established by principal component analysis,
and discomfort and experience in weight loss and
exercise were investigated by t-test (unpaired).
Meanwhile, the relationship with physique at birth,
current physique, and genetic factors was analyzed
Table 1. Characteristics of participants N = 146mean SD range
Age (years) 20.3 1.1 18~23Height (cm) 157.47 5.26 141.3~169.8Body fat percentage (%) 25.0 5.2 9.6~41.6BMI (kg/m2) 20.39 1.61 14.4~32.7
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
by correlation coefficient and multiple regression
analysis (stepwise). Excessively long participants
were those whose interspinal, intercristal, or
intertrochanteric diameter was longer than the
standard value by 2 cm or more, or whose external
conjugate or external oblique diameter was
longer than the standard value by 1 cm or more.
Excessively short participants were those whose
interspinal, intercristal, or intertrochanteric diameter
was shorter than the standard value by 2 cm or
more, or those whose external conjugate or external
oblique diameter was shorter than the standard value
by 1 cm or more.
4. Ethical considerations
Participant recruitment posters listed research
objectives, methods of data collection, management
and handling of personal information, and the
method used for reporting results. On the day of
measurement, the same information was explained
verbally and in writing, and written consent was
obtained. This study was approved by the Hiroshima
International University School of Nursing ethics
committee in March 2010, and was conducted in
accordance with the Declaration of Helsinki.
Results1. Features of the participants’ pelvic shapes
Participants’ characteristics are shown in Table
1. Most participants had a standard physique, with
73.3% having a BMI of 18.5 to less than 25, and
69.2% having a body fat percentage of 20% to less
than 30%.
The values of the diameter lines measured
in this study were compared against standard
measurement values, and the intertrochanteric
diameter was significantly longer (p < .05). The
interspinal diameter, intercristal diameter, external
conjugate, and external oblique diameter in turn
tended to be short, though not significant (Table
2). Of all participants, 56.2% had one excessively
short diameter line. The platypelloid participants,
in whom the difference between the interspinal and
intercristal diameters was less than the standard
value, accounted for 38.4% of the participants.
Similarly, the ratio of the intertrochanteric diameter
to the external conjugate was greater than the
standard value by 1.5, with some 93.8% presumed
to have a large transverse diameter of the pelvis.
2. Relationship with physique
In the relationships between the diameter lines,
and pelvic score and physique (height, weight,
BMI, and body fat percentage), a moderate to
strong positive correlation was observed in all the
relationships, excluding the interspinal diameter and
some external conjugate (Table 3). The difference
between the intercristal and interspinal diameters
showed a weak correlation with weight, BMI,
and body fat percentage, with thinner individuals
Table 2. Pelvic size and balance of young women
DiameterStandard
measurement(Nakanishi, 2002)
N=146Average (SD) cm
Excessively short 1)
%Excessively long 2)
%
Sp 23.0 22.40 (1.68) 11.6 8.9Cr 26.0 25.63 (1.87) 13.0 13.7Tr 28.0 31.13 (2.01) 1.4 84.2
Sch 21.0 20.63 (2.01) 34.9 30.1Ext 19.0 18.36 (1.65) 34.9 18.5
Cr-Sp 3.0 3.23 (1.41)Tr / Ext 1.5 1.71 (0.14)
Note. Sp: interspinous diameter, Cr: intercristal diameter, Tr: intertrochanteric diameter, Sch: external oblique diameter, Ext: external conjugate diameter
1) Excessively short participants were those whose interspinal, intercristal, or intertrochanteric diameter was shorter than the standard value by 2 cm or more, or those whose external conjugate or external oblique diameter was shorter than the standard value by 1 cm or more.
2) Excessively long participants were those whose interspinal, intercristal, or intertrochanteric diameter was longer than the standard value by 2 cm or more, or whose external conjugate or external oblique diameter was longer than the standard value by 1 cm or more.
Table 3. Relationship with pelvic size and physique N = 146Hight Weight BMI Body fat percentage
Sp .421 *** .298 *** .145 .275 **Cr .315 *** .472 *** .385 *** .450 ***Tr .427 *** .601 *** .463 *** .543 ***
Sch .304 *** .609 *** .540 *** .591 ***Ext .276 ** .727 *** .677 *** .687 ***
Cr-Sp -.082 .274 ** .339 *** .272 **Tr / Ext -.152 -.133 -.163 -.133
Pelvic score .451 *** .700 *** .572 *** .659 ***
Note. Pearson’s coefficient of correlation, *p < .05, **p < .01, ***p < .001
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Pelvic shape of contemporary young women: Related factors and impact on daily life
showing a tendency to be platypelloid (r = .27 ~ .34,
p < .01). However, the intertrochanteric diameter-
to-external conjugate ratio, which is indicative of
the balance between the length and breadth of the
pelvis, exhibited no relationship with physique.
Thus, a multiple regression analysis was
performed, with the pelvic score as a dependent
variable, and height, weight, body fat percentage,
and BMI as independent variables. BMI was
excluded by stepwise procedure. Three models were
extracted, having a multiple correlation coefficient
R2of .5 or higher and a highly accurate prediction
of the multiple regression formula. Therefore, a
model was used that had a high multiple correlation
coefficient and low VIF, with height and body fat
percentage as independent variables (R2 = .532, VIF
Table 4. Relationship between pelvic size, and dieting experience and exercise experience
Dieting experience Exercise experience
Differences from non experienced group (cm) p value Differences from non
experienced group (cm) p value
Sp .33 .25 -.04 .92Cr .37 .22 -.05 .89Tr .79 .02 -.39 .36
Sch .59 .08 -.39 .35Ext .42 .12 -.10 .77
Cr-Sp .04 .86 -.01 .96Tr / Ext .02 .33 -.02 .51
Pelvic score .34 .04 -.12 .55
Note. Unpaired t-test
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
= 1.044). The standardized coefficients were .329 (p
= .000) for height and .592 (p = .000) for body fat
percentage, and pelvic score was strongly affected
by body fat percentage.
3. Relationship between physique at birth and
genetic factors
No significant relationships were observed
for height and weight at birth and various pelvic
diameter lines and pelvic score. Height at the one-
month health check was not noted in one third of the
participants’ Maternal and Child Health Handbooks.
We examined only those 107 participants who did
have data. We observed weak positive correlational
relationships of height with intercristal, interspinal,
and intertrochanteric diameter (r = .24 ~ .35, p
< .05). In addition, we observed weak positive
correlational relationships of the mother's height
with intercristal, interspinal, and external conjugate
diameters, and the mother's weight with intercristal
and external conjugate diameter (r = .26 ~ .27, p <
.01).
4. Relationship with previous lifestyle
Examining the relationship between pelvic size,
and dieting and exercise experience, we found that
those with dieting experience tended to have larger
pelvises, with significant differences particularly in
intertrochanteric diameter (t (141) = 2.31, p = .02)
and pelvic score (t (141) = 2.04, p = .04). However,
no relationship was observed between exercise
experiences since junior high school, such as group
activities, and the pelvic size or balance (Table 4).
5. Relationship with discomfort in daily life
Of the 17 symptoms causing discomfort in daily
life, a mean of 6.5 (SD 2.8) symptoms per participant
was recorded. The most frequent symptoms were
fatigability, leg coldness, stiff neck, irritability,
abdominal bloating, and swelling, with the first five
top five symptoms observed at least 80% of the
time.
Therefore, the relationships between individual
symptoms, and pelvic size and balance were
examined (Table 5). The results showed that those
with leg swelling or stiff neck tended to have larger
pelvises and had significantly larger transverse
Table 5. Relationship with pelvic size and discomforts
incidence rate(%) Sp1) Cr1) Tr1) Sch1) Ext1) Tr/Ext1) Cr-Sp1) Pelvic1) score
Pelvic pain 16 (11.2) 1.16*Stiff shoulder 89 (62.2) .07** .49*
Abdominal compression 83 (58.0) .67*
Incontinence of urine 7 (4.9) .52*
Varix 2 (1.4) -.26**Cold hands 74 (51.7) -.57*
Cold hip 29 (20.3) .96* .77*Swelling of leg 77 (53.8) 1.06**
Fatigability 111 (77.6) .85*
Note. Unpaired t-test, *p < .05, **p < .01, ***p < .0011) Numbers indicate differences of mean from those without discomforts.
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Pelvic shape of contemporary young women: Related factors and impact on daily life
diameters. Those who had urinary incontinence
and abdominal bloating also showed a tendency to
have larger pelvises and larger transverse diameters.
Those with hip coldness or pelvic pain had large
pelvises, with many having a long anteroposterior
diameter. Participants with pelvic pain or fatigability
had a large first external conjugate but had no other
diameter line showing a significant difference from
those without symptoms.
Discussion This study used external pelvimetry, frequently
employed in the 1970s and 1980s, to better
understand pelvic size and balance in contemporary
women in early maturity, and to examine the
influencing factors and their impact on daily life.
Results show that intertrochanteric diameter is
longer than the standard value, all other diameters
were shorter than the standard, with a change
believed to have taken place in the pelvic balance.
The impact on life was also clarified.
1. Features of pelvic shape in contemporary women
In clinical settings, narrowing and imbalance
have been observed in women’s pelvises. This study
found a tendency for each of the pelvic diameter
lines to be shorter than the standard value, and only
the intertrochanteric diameter (mean, 31.1 cm)
was significantly longer than the standard value
(28 cm). Other recent investigations have reported
similar results; Minohara, et al. (2003) reported a
length of 29.7 cm and Doi, et al. (2012) reporting
30.7 cm. The only negative aspect of using external
pelvimetry is the possibility of errors committed
by the measurer. According to Masuzaki, et al.
(1991), the error at the intertrochanteric diameter
is smallest with a mean of 3.0% of the coefficient
of variation, so the intertrochanteric diameter could
be said to have been increased. However, a survey
of adolescent girls conducted in 1970 (Tokue,
1970) revealed that the intertrochanteric diameter
already exceeded 30 cm at the age of 18. The
intertrochanteric diameter is the length between the
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
left and right greater trochanters. Thus, in terms
of position, the intertrochanteric diameter is less
susceptible to changes in the balance between the
anteroposterior and transverse diameters associated
with development of the pelvis, for which reason it
is similar to the values reported in the 1970s.
Women’s pelvic areas can be classified into
the anthropoid, circle, and platypelloid types.
Narumoto, et al. (2013) investigated changes in
type distribution in women’s pelvic inlet areas via
radiography at the end of pregnancy, and found
that the most common type in the 1960s, circle,
had fallen from 60% to 45% of pelvic areas, and
an increase of from 8% to 47% in the anthropoid
type, which has a longer anteroposterior diameter.
Because the intertrochanteric diameter was extended
in this study, there was a higher value for the ratio
of the intertrochanteric diameter and external
conjugate, which has been long used to assess the
balance between the anteroposterior and transverse
diameters of the pelvis. The mean interspinal
diameter, which has a high correlation with the
transverse diameter of the pelvic inlet area, was
shorter, though not significantly so. For reference,
when the ratio between the interspinal diameter and
external conjugate (standard: 23 / 29 = 1.21) and the
ratio between the intercristal diameter and external
conjugate (standard: 26 / 19 = 1.37) were examined,
the proportion of participants for whom the ratio
was smaller than the standard value were 45.9%
and 41.8%, respectively. In this study we see that
contemporary women’s pelvic inlet areas cannot be
said to have become more slender and elongated.
Although the transverse diameter might appear
larger than the extension of the intertrochanteric
diameter when general indices are used, no major
change from the standard values was observed in the
balance of the pelvic inlet area.
Meanwhile, the intertrochanteric diameter is
strongly related to the anteroposterior diameter
of the midpelvis (Masuzaki, et al., 1991), and
the anteroposterior diameter of the midpelvis is
believed to have become larger. Originally, the
oblique diameter was greatest for the midpelvis. For
this reason, the fetus can turn the second rotation
unencumbered during delivery. However, to say
that the midpelvis had a greater anteroposterior
diameter would also mean that the second
rotation is completed well before the fetal head
reaches the narrow pelvic part, and this could
be a cause of abnormal rotation. According to
Maeda, et al. (1998), the cesarean delivery rate for
intertrochanteric diameters of 28 cm and greater
is 5.8%. There is also the possibility that in the
future an increase in women with more developed
intertrochanteric diameters could increase the rate of
cesarean delivery.
As has been noted (Sakamoto, et al., 1998),
screening contemporary young women for narrow
pelvis due to conjugataveraobstetrica is not
meaningful. This means that cesarean delivery rates
for women with an external conjugate of less than
17.5 cm, or with a conjugatavera obstetrica of less
than 9.5 cm, these two having been standards in the
past, are lower than for women with an inlet area
transverse diameter less than 10.5 cm (C-section
rates for the above are 5.2%, 40.0%, and 72.7%,
respectively). Maeda, et al. (1993) have also
reported more women taller than the standard height,
which indicates that measured values are longer
than the standard values, and that balance is also
important. This suggests that the standard values
need to be reviewed for contemporary women,
and that each of the diameter lines also need to be
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Pelvic shape of contemporary young women: Related factors and impact on daily life
reassessed by balance.
2. Factors associated with pelvic size
The length of each of the pelvic diameter lines
have been strongly related to height, and in clinical
practice the standard is to consider assessing women
for narrow pelvises, and therefore high-risk delivery,
if they are shorter than 150cm, and especially if they
are shorter than 145cm. However, in recent years,
questions have emerged regarding the relationship
between height or physique and pelvic size (Chihara,
et al., 2010; Doi, et al., 2012). The physiques of
Japanese women have improved rapidly, mostly in
height, from the first half of the 1900s until 1990.
Thus, when compared to the pelvises of women from
Japan’s Meiji era (1868-1912), mean height increase
has had a considerable impact on the development
of each of the diameter lines (Minohara, et al.,
2003). Since 1990, however, women’s physiques
have gone unchanged (Ministry of Internal Affairs
and Communications, 2013). In this study, the
relationship of height to each of the diameters was
weaker than those of body fat percentage (r = .45
– .69, p < .001) and BMI (r = .39 – .68, p < .001).
The lower the weight, BMI, or body fat percentage,
the smaller the difference between the intercristal
and interspinal diameters; thus, the thinner women
become the more they tend to be platypelloid.
A girl’s height and pelvic size are greatly
influenced by her birth mother’s height, until age
14, and then are influenced by paternal height
thereafter (Togo, et al., 1988). This survey, which
studied female students, found a weak correlation
between each of the pelvic diameter lines and the
birth mother’s height or weight. No correlation to
the respondent’s own physique at the time of birth
was found. These results show that pelvic size and
balance is influenced more by nutrition factors than
by received genetic attributes or birth weight and
height. Therefore, in future screening for narrow
pelvis it is recommended to use BMI or body fat
percentage instead of height.
3. Impact on daily life
As also shown in this study, contemporary women
in early maturity often have discomfort in their
daily lives. Therefore, this study considered whether
pelvic size or balance was related to the onset of
discomfort. In particular, leg swelling or numbness,
coldness, and varicose veins are clinically known
to be related to disturbances of the autonomic
nervous system and poor circulation in the pelvis.
We therefore predicted we would find more women
with a relatively small pelvis or with a pelvis that
tends to be flat. Unexpectedly, the results of this
study show that women with large pelvic diameter
lines have a higher incidence of these discomforts,
and in particular, there are numerous women with
development reaching the transverse direction.
Therefore, the relationship with pelvic size requires
future investigation.
Women with pelvic pain or fatigability had
larger first external conjugates. This survey did
not measure distortion of the pelvis, but the fact
that diameter lines, other than the first external
conjugate, had no difference from participants
without discomforts suggests pelvic distortion.
Minohara, et al. (2003) have reported a lack of
correlation between pelvic distortion in daily habits
such as holding a bag, sitting, or having the center of
gravity concentrated on one side. Causes of pelvic
distortion will require further examination.
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広島国際大学看護学ジャーナル 第11巻 第1号 2013
4. Implications for nursing and midwifery
A woman’s pelvis is important for protecting and
nurturing a fetus for 9 months, but at the same time,
it serves as a birth canal during birth. Therefore, its
shape is of considerable obstetric importance. As
medical technology has advanced it has become
possible to measure pelvic shape more accurately.
The amount of radiographic exposure has also been
successfully improved, with no substantial effect
observed on the fetus or on pregnant women in late
pregnancy. Nonetheless, radiography should not be
used in all pregnant women. Low height is used to
identify high-risk groups, however, women who are
slender or have a low body fat percentage have also
been considered as being at high-risk.
Data on the application of external pelvimetry
have been accumulated over several years and
is now considered a safe and simple assessment
method. The present results suggest the need to
update to new standard measurement values and
make indices for assessing balance by collecting
data on contemporary women.
5. Limitations of the study and future challenges
Japan’s contemporary women are very self-
conscious of their physique, in particular weight,
and 40% of our participants had dieted for weight
loss. People who diet generally have repeatedly
done so since youth, and secondary amenorrhea,
common in adolescence, has been related to excess
weight loss. Tokue (1970) noted that with secondary
amenorrhea, the pelvic diameter lines were smaller
than the standard, and the increasing dieting time
during youth is presumed to substantially impact the
health of future mothers and the development of the
pelvis by which the next generation will be born.
In this study, body fat percentage was shown to
be considerably related to pelvic size and balance in
women in early maturity, so an attempt was made
to also examine the relationship with weight loss.
Results show that women who had dieted for weight
loss had larger diameter lines. However, the BMI
and body fat percentage of those with experience
dieting were significantly higher than those who had
never dieted, and results during weight loss were
not surveyed. Therefore, we could not conclude
that dieting during pelvic development is associated
with delayed development of the pelvis. Future
improvements to the questionnaire would contribute
more meaningful assessment.
In conclusion, this study has clarified the
following regarding the assessment of pelvic size
and balance by external pelvimetry: contemporary
women in ear ly matur i ty show signif icant
development of the pelvis in the intertrochanteric
diameter but no major changes in other diameter
lines. Development of the intertrochanteric diameter
is associated with a higher intertrochanteric
diameter-to-external conjugate ratio, but the overall
pelvic balance showed no remarkable change. Pelvic
size and balance were only slightly influenced
by physique at birth and by genetic factors, and
the current body fat percentage was of significant
relevance to pelvic size. Of the forms of discomfort
in daily life, women who have leg swelling, stiff
neck, urinary incontinence, or abdominal bloating
have larger pelvises, especially in the transverse
direction, than women who do not have these
symptoms. Women with pelvic pain or fatigability
had larger external conjugates.
Acknowledgments We wish to thank all the participants who
cooperated with this s tudy and Hiroshima
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Pelvic shape of contemporary young women: Related factors and impact on daily life
International University’s Yuka Saito and Maki
Sugino for their assistance. This study received a
special research grant from Hiroshima International
University.
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