B Dujardin

BC Chan

BJ McGuinness

E Sheiner

F Kara

HB Liselele

Kasemsri Srisupundit

Maternal anthropometry and pregnancy outcomes

MC Hogan

MK Bohlmann

Rusleena Toh-adam

Sub-committe of Maternal and Child Health

TA Mahmood

Theera Tongsong

English

PubMed

Crossref

Archives of Gynecology and Obstetrics

Short stature as an independent risk factor for cephalopelvic disproportion in a country of relatively small-sized mothers

Springer - Publisher Connector

Arch Gynecol Obstet (2012) 285:1513–1516
DOI 10.1007/s00404-011-2168-3
MATERNAL-FETAL MEDICINE
Short stature as an independent risk factor for cephalopelvic 
disproportion in a country of relatively small-sized mothers
Rusleena Toh-adam · Kasemsri Srisupundit · 
Theera Tongsong 
Received: 14 August 2011 / Accepted: 28 November 2011 / Published online: 21 December 2011
© The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract
Objective To clarify the relationship between maternal
height and cesarean rate due to cephalopelvic disproportion
(CPD) in singleton pregnancies among ethnic groups of rel-
atively short stature.
Methods A retrospective cohort study was performed on
Thai singleton pregnancies at gestational age of more than
34 weeks. Logistic regression analysis was performed to
correlate the maternal height and a risk for CPD. The short
stature was deWned by a cut-oV value at 5th percentile rank-
ing. Odds ratio for CPD was determined.
Results Of 11,026 recruited, 9,198 were available for analy-
sis. Considering cut-oV value of 145 cm, short stature was sig-
niWcantly associated with higher rate of CPD with odds ratio of
2.4 (95% CI 1.8–3.0). The odds = exp(4.048 ¡ 0.042 £ Ht).
After control of other variables, the relationship between
maternal height and rate of CPD was still high.
Conclusion Mothers with short stature were signiWcantly
correlated with a higher rate of CPD, even after control of
birth weight, parity and type of attendance. Clinical points
could be drawn from this study including (1) deWnition of
short statue must be developed for particular geographic or
ethnic groups. In Thai population, using 145 cm as a cut-oV
value, odds of CPD is 2.4; (2) Probability of CPD may be
estimated by maternal height as a single variable or multi-
ple variables using logistic regression equations.
Keywords Cephalopelvic disproportion · Cesarean 
section · Maternal height · Short stature
Introduction
Maternal morbidity and mortality remain a major challenge
to health systems worldwide, especially in developing
countries. Recent estimates indicate that more than 300,000
women die worldwide in 2008 [1]. In developing countries,
a signiWcant number of maternal deaths are attributable to
the complications of obstructed labor leading to birth canal
trauma, postpartum hemorrhage, and genital infections, etc.
Of patients with dystocia, delay in the decision to seek care
or delay in arrival to an appropriate medical care facility is
common in rural hospitals. Detection of mothers at a higher
risk of dystocia is therefore important for higher precaution,
close attention or preparation of cesarean section or timely
labor induction in daytime when more manpower and expe-
rienced physicians are available. This is particularly crucial
in settings where cesarean section is not feasible, so that
women at high risk for CPD may be referred to a hospital
equipped with an operating theatre before the onset of
labor. Maternal height reXecting maternal pelvic size,
which is related to dystocia, has been shown to be predic-
tive for obstructed labor [2–8]. Indeed, maternal height, as
a simple tool requiring no any special skills, has been
investigated extensively especially in developing countries
for predicting obstructed labor. However, whereas the
inverse relationship between maternal height and the cesar-
ean rate has been consistently demonstrated, the application
of height to predict risk of obstructed labor or cesarean sec-
tion remains controversial. Furthermore, no universal deW-
nition of short stature in pregnant women has been well
accepted. This is due to the fact that maternal height distri-
bution is varied among diVerent geographic or ethnic
groups of study. Thai or Southeast Asian mothers are typi-
cally shorter than those in western. Certainly, application of
maternal height on clinical practice based on studies in
R. Toh-adam · K. Srisupundit · T. Tongsong (&)
Department of Obstetrics and Gynecology, 
Faculty of Medicine, Chiang Mai University, 
Chiang Mai, Thailand
e-mail: ttongson@mail.med.cmu.ac.th123
1514 Arch Gynecol Obstet (2012) 285:1513–1516other parts of the world is inappropriate. Therefore, this
study aimed to determine the eVectiveness of maternal
height in predicting risk of cesarean section due to cephalo-
pelvic disproportion among Thai population.
Patients and methods
A retrospective cohort study was conducted at Maharaj
Nakorn Chiang Mai Hospital, Chiang Mai University,
Thailand during 2006–2010. This study was ethically
approved by the local institutional review board. The
database of maternal-fetal medicine unit and some medi-
cal records was reviewed for baseline characteristics,
maternal height and labor outcomes. Some missing data,
especially the maternal height, were traced from the
patients either by mail, phone or direct search of census
registration from Department of Provincial Administra-
tion. Details of delivery were prospectively recorded by
the obstetricians and computerized collected everyday
by the research supporting nurse. Inclusion criteria were
(1) gestational age of greater than 34 weeks based on
overall clinical estimation of medical records, (2) sin-
gleton pregnancies, and (3) available data of delivery
method with indication of cephalopelvic disproportion
(CPD). In our practice, CPD or the failure to progression
of labor is deWned as suggested by the Royal Thai Col-
lege of Obstetricians and Gynecologists [9], as follows:
(1) active phase of labor deWned by cervical dilatation of
at least 4 cm and 80% eVacement, (2) regular and ade-
quate uterine contractions at least 2 h before decision
making, and (3) abnormal partograph, such as protrac-
tion disorders, arrest disorders or second stage failure to
descend. Variables included for analysis were maternal
height, maternal age, parity, type of attendance (private
or general antenatal care), birth weight and delivery
methods. The pregnant women were categorized into
several subgroups based on percentile ranking of mater-
nal height distribution, parity, and type of attendance.
The main outcome was cesarean section rate indicated
by CPD in various subgroups of maternal height.
Statistical analysis
Means and standard deviation for diVerent variables in each
group were calculated and tested for signiWcance. Odd
ratios with 95% conWdence intervals for cesarean rate due
to CPD in various groups of maternal height were
determined. p < 0.05 was considered statistically signiWcant.
A logistic regression analysis was performed to identify if
there was a particular height as well as other variables such
as maternal age, parity or type of attendance at which the
risk of having a cesarean section increased signiWcantly.
Results
During the study period, 11,026 singleton deliveries were
reviewed. Of them, 1,828 were excluded due to incomplete
data of either labor outcomes or maternal height. The
remaining 9,198 were available for analysis. Of these,
5,201 (56.5%) were nulliparous and 3997 (43.5%) were
multiporous women. In addition, most mothers (7,743;
84.2%) attended the general antenatal clinic, taken care by
rotating obstetricians while 1,455 (15.8%) were taken care
by one special obstetrician as a private service. The
means § SD (range) of maternal age, gestational age at
delivery, and birth weight were 28.02 § 6.02 year (13–
44 years), 38.19 § 1.54 weeks (34–43 weeks), and 2,983.7
§ 447.9 g (1,790–5,300 g), respectively. The means § SD
(range) maternal height was 155.4 § 6.2 cm (100–192 cm),
median (50 percentile) was 155.0 cm. The percentile distri-
bution of the maternal height at 5, 10, 20, 50, 80, 90, 95
percentile were 145, 148, 150, 155, 160, 163 and 165 cm,
respectively.
In a total of 9,198, methods of delivery included normal
vaginal delivery; 70.2%, operative vaginal delivery; 7.5%,
and cesarean section; 22.3%. The cesarean section rate due
to CPD was 8.1% of all deliveries. Of interest, overall
cesarean section rate in the mothers of nulliparity was
slightly but signiWcantly lower than that in the multiparous
group (20.7 vs. 24.4%; p < 0.001, odds ratio 0.92). Never-
theless, conversely, cesarean rate secondary to CPD was
markedly higher among the nulliparous group (12.2 vs.
2.7%; p < 0.001, odds ratio of 4.9).
The rates of cesarean section due to CPD with odds ratio
in the groups categorized by maternal height and type of
attendance, and parity are presented in Table 1. In the group
of short maternal height, using a cut-oV value of 145 cm,
had a cesarean rate of 16.3% and odds ratio of 2.4. Note
that the rate of cesarean section due to CPD declined from
16.3% at cut-oV 145 cm to 11.4% at 150 cm and 9.6% at
155 cm. Interestingly, the cesarean rate due to CPD in the
private service was 13.6% with odds ratio of 2.1.
Table 1 Cesarean section rate and odds ratio according to categorized
groups
No. of CPD CPD Odds ratio (95% CI)
Height ·145 cm 402 (83.8%) 78 (16.3%) 2.353 (1.824–3.037)
Height ·150 cm 1803 (88.6%) 233 (11.4%) 1.689 (1.434–1.989)
Height ·155 cm 4336 (90.4%) 460 (9.6%) 1.550 (1.328–1.808)
Private cases 1257 (86.4%) 198 (13.6%) 2.085 (1.753–2.479)
Nulliparity 4568 (87.8%) 633 (12.2%) 4.943 (4.016–6.084)123
Arch Gynecol Obstet (2012) 285:1513–1516 1515When short stature was deWned by a cut-oV value of
145 cm, the means § SD of maternal age of the short and
normal mothers were not signiWcantly diVerent (27.6 § 6.1
vs. 28.0 § 6.0 years, p > 0.05) while the means § SD of
birth weight in the short mothers was signiWcantly lower
than that in the normal height group (2854 § 430 vs.
2991 § 447 g, p < 0.05).
In logistic regression analysis using maternal height as a
single-independent variable, it was found that maternal
height was signiWcantly correlated with rate of cesarean
section due to CPD (p < 0.0001). The equation of relation-
ship is as follows (Fig. 1):
• Odds = exp(4.048 ¡ 0.042 £ Ht); where, Ht is maternal
height in cm, odds represents a ratio of probability of
cesarean section to probability of vaginal delivery.
Other variables which were found to be signiWcant in multi-
ple logistic regression analysis included maternal age, birth
weight, parity, and private service. The equation is as
follows:
• Odds = exp(¡1.455 ¡ 0.078 £ Ht + 0.085 £ age + 0.002 £
BW + 0.566 £ private + 2.427 £ parity); where, Ht is
maternal height in cm, age represents maternal age in
years, private is 1 if taken care in private service, parity
is 1 for nuliparity).
Discussion
Though several studies have been published on this issue,
our study was unique in terms of particular ethnic group
and our Wndings should encourage all other groups around
the world to evaluate the risk based on height distribution
among their own population.
In our practice, we usually use a 145-cm cut-oV value for
diagnosis of short stature, labeled as high risk, certainly
diVerent from that in the western since our mothers have a
relatively small size, nevertheless this routine practice has
never been evaluated for appropriateness. As seen in the
results, despite the tendency to have relatively small
infants, mothers with short stature were more likely to have
a higher chance of obstructed labor. Based on our study,
whereas other variables are not considered, a cut-oV value
of 145, consisting of 5% of our obstetric population, is jus-
tiWed since the rate of CPD is about 16.3% and odds ratio of
2.4 while the overall cesarean rate was 8.1%. Therefore,
maternal height may be used as a simple tool to screen a
risk factor for CPD and the need for highly specialized
care. The logistic regression analysis has demonstrated a
curve with a gradual decrease in the risk of cesarean section
due to CPD with increasing maternal height. This relation-
ship is a useful guide for counseling the couple in terms of
clinical risk for cesarean section. However, in real practice,
other variables other than maternal height are usually taken
into account. Certainly a short mother with estimated low
birth weight does not carry a high risk for CPD. Though a
little more complicated, the equation derived from multiple
logic regression analysis in this study may be helpful to
quantify risk with more accuracy. Indeed, in the era of digi-
tal world, probability and odds calculation for cesarean sec-
tion for CPD based on equation mentioned above are
readily anywhere even in the rural area. Therefore, we sug-
gest multiple logistic regression equation in risk calculation
rather than maternal height alone.
Note that, we did not include mothers with gestational
age of less than 34 weeks of gestation, since it is very rare
in our practice to encounter CPD at such early gestation
regardless of maternal height.
The study involved population in which the mothers are
shorter than other groups ever studies even in Asian groups
like Japanese [10]. Our data also suggest that a higher
cesarean rate due to CPD should be expected for Thai pop-
ulation or probably Southern Asian mothers with shorter
stature, even for those with relatively small babies. This
information is important for appropriate counseling of the
couple, especially in developing countries or even in devel-
oped countries with mixed ethnic groups. Information on
higher risk for CPD is essential for good clinical practice.
Higher precaution must be given for mothers with a higher
risk in term of close attention or preparation of cesarean
section or timely labor induction in daytime when more
manpower and experienced physicians are available.
This study has demonstrated that maternal height was
inversely correlated with a rate of cesarean delivery sec-
ondary to cephalopelvic disproportion. As already known,
maternal height in our population is certainly shorter than
that in the western population. Therefore, we Wrst
Fig. 1 Correlation between maternal height and predicted probability
for cesarean section due to CPD regardless of other variables123
1516 Arch Gynecol Obstet (2012) 285:1513–1516determined the percentile range of height distribution in our
pregnant women, and then categorized them based on the
height percentile groups. The height distribution in this
study suggested that the height of 145 cm may be an
appropriate cut-oV for short stature in Thai population,
instead of adopting a particular cut-oV value as recom-
mended in several previous studies which are in range of
150–160 cm [4, 6, 7, 11].
Obviously, simply adopting a cut-oV value of either 150
or 155 or 160 cm to deWne short stature in Thai or other eth-
nic groups in the same geographical area such as Laotian or
Cambodian is inappropriate. For example, with deWnition
of 155 cm as a cut-oV value which is a Wfth percentile value
for German [8], 60% of our population, instead of 5% as
suggested by several authors, would be classiWed as high
risk for CPD and be likely to result in inconclusive results.
That is an unacceptably great number for taking care of
mothers at high risk.
In spite of the fact that the shorter in maternal height, the
lower in birth weight, maternal height is inversely
correlated with a higher risk of cesarean delivery due to
cephalopelvic disproportion. The eVect of maternal height
on such cesarean rate seems to be continuous without deW-
nite cut-oV point.
Based on our study and other previous studies in the
western, the criterion for short stature should be deWnitely
based on ethnic groups and must be categorized according
to height percentile range rather than absolute height may
allow comparison between diVerent populations on the
eVect on labor outcome.
Certainly, birth weight is directly correlated to cesarean
section rate due to CPD. In fact, infants born to mothers
with normal height and CPD were heavier than those
without CPD. Conversely, less heavy infants born to moth-
ers with short stature might have been able to deliver nor-
mally. Nevertheless, after addition of birth weight in the
logistic regression model, the correlation between CPD and
maternal height remained high. Furthermore, mean birth
weight in the group of short stature was less than that of the
normal group. Therefore, it may be of value to combine
maternal height and estimated fetal weight to assess the risk
of CPD, though prenatally estimated birth weight may be
not perfectly accurate. Likewise, nulliparity and private
service signiWcantly contributed to a higher risk for CPD
and should also be taken into account.
In conclusion, mothers with short stature were indepen-
dently correlated with a higher rate of CPD. Clinical points
could be drawn from this study including (1) deWnition of
short statue must be developed for particular geographic or
ethnic groups. In Thai population, using 145 cm as a cut-oV
value, odds of CPD is 2.4; (2) probability of CPD may be
estimated by maternal height as a single variable or
multiple variables using logistic regression equations.
Acknowledgments We wish to thank the National Research Univer-
sity Project under Thailand’s OYce of the Higher Education Commis-
sion for Wnancial support.
ConXict of interest No conXict of interest.
Open Access This article is distributed under the terms of the Cre-
ative Commons Attribution Noncommercial License which permits
any noncommercial use, distribution, and reproduction in any medium,
provided the original author(s) and source are credited.
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Diagnostic guideline for cesarean section due to cephalopelvic disproportion or failure to progress of labor.

Diedrich K et al (2010) Nulliparous patients with small stature delivering at term have an increased risk of secondary cesarean section.

Maternal height and external pelvimetry to predict cephalopelvic disproportion in nulliparous African women: a cohort study.

Maternal height as a risk factor for Caesarean section due to failure to progress in labour.

Maternal height as a risk factor for Caesarean section.

Maternal height, shoe size, and outcome of labour in white primigravidas: a prospective anthropometric study.

Maternal mortality for 181 countries, 1980–2008: a systematic analysis of progress towards Millennium Development Goal 5.

Short stature—an independent risk factor for Cesarean delivery.

The impact of maternal height on intrapartum operative delivery: a reappraisal.

The value of maternal height as a risk factor of dystocia: a meta-analysis.

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Short stature as an independent risk factor for cephalopelvic disproportion in a country of relatively small-sized mothers

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