Abstract Background During the last 20 years the rate of CS has increased in Sweden as it has in many other countries. The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time period. It would therefore be of interest to study both how and if these two observations are related to each other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight of pregnant women. Method The design is a retrospective cohort study using medical records of consecutively delivered women at two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001. Results No significant time-trends were found for CS and instrumental delivery within each BMI-group for the time period studied. The proportion of women with BMI ≥ 25 delivered by means of CS or instrumental delivery increased quite dramatically from 1978 to 2001 (χ2 test for trend; p < 0.001 for both CS and instrumental deliveries). The mean birth weight in relation to BMI and year of study among women delivered by means of CS decreased, a trend that was most evident between 1997 and 2001 (F-test; p = 0.005, p = 0.004, and p = 0.003 for BMI < 20, 20-24.9, and ≥ 25, respectively). Conclusion Overweight and obese pregnant women constitute a rapidly growing proportion of the total number of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its implications.</p

Adam Sydsjö

Ann Josefsson

G Barau

G Sydsjö

GC Lu

Gunilla Sydsjö

J Brynhildsen

Jan Brynhildsen

JL Weiss

M Cedergren

N Heslehurst

P Puska

S Cnattingius

TS Usha Kiran

World Health Organisation

English

PubMed

ABSTRACT: BACKGROUND: During the last 20 years the rate of CS has increased in Sweden as it has in many other countries. The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time period. It would therefore be of interest to study both how and if these two observations are related to each other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight of pregnant women. METHOD: The design is a retrospective cohort study using medical records of consecutively delivered women at two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001. RESULTS: No significant time-trends were found for CS and instrumental delivery within each BMI-group for the time period studied. The proportion of women with BMI andgt;/= 25 delivered by means of CS or instrumental delivery increased quite dramatically from 1978 to 2001 (chi2 test for trend; p andlt; 0.001 for both CS and instrumental deliveries). The mean birth weight in relation to BMI and year of study among women delivered by means of CS decreased, a trend that was most evident between 1997 and 2001 (F-test; p = 0.005, p = 0.004, and p = 0.003 for BMI andlt; 20, 20-24.9, and andgt;/= 25, respectively). CONCLUSION: Overweight and obese pregnant women constitute a rapidly growing proportion of the total number of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its implications

Sydsjö, Gunilla

Sydsjö, Adam

Brynhildsen, Jan

Josefsson, Ann

Digitala Vetenskapliga Arkivet - Academic Archive On-line

Trends in caesarean section and instrumental deliveries in relation to Body Mass Index: a clinical survey during 1978 - 2001

Abstract Background During the last 20 years the rate of CS has increased in Sweden as it has in many other countries. The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time period. It would therefore be of interest to study both how and if these two observations are related to each other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight of pregnant women. Method The design is a retrospective cohort study using medical records of consecutively delivered women at two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001. Results No significant time-trends were found for CS and instrumental delivery within each BMI-group for the time period studied. The proportion of women with BMI ≥ 25 delivered by means of CS or instrumental delivery increased quite dramatically from 1978 to 2001 (χ2 test for trend; p Conclusion Overweight and obese pregnant women constitute a rapidly growing proportion of the total number of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its implications.</p

Josefsson Ann

Brynhildsen Jan

Sydsjö Adam

Sydsjö Gunilla

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Reproductive Health

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RESEARCH Open Access
Trends in caesarean section and instrumental
deliveries in relation to Body Mass Index:
a clinical survey during 1978 - 2001
Gunilla Sydsjö*, Adam Sydsjö, Jan Brynhildsen, Ann Josefsson
Abstract
Background: During the last 20 years the rate of CS has increased in Sweden as it has in many other countries.
The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time
period. It would therefore be of interest to study both how and if these two observations are related to each
other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among
women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight
of pregnant women.
Method: The design is a retrospective cohort study using medical records of consecutively delivered women at
two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001.
Results: No significant time-trends were found for CS and instrumental delivery within each BMI-group for the
time period studied. The proportion of women with BMI ≥ 25 delivered by means of CS or instrumental delivery
increased quite dramatically from 1978 to 2001 (c2 test for trend; p < 0.001 for both CS and instrumental
deliveries). The mean birth weight in relation to BMI and year of study among women delivered by means of CS
decreased, a trend that was most evident between 1997 and 2001 (F-test; p = 0.005, p = 0.004, and p = 0.003 for
BMI < 20, 20-24.9, and ≥ 25, respectively).
Conclusion: Overweight and obese pregnant women constitute a rapidly growing proportion of the total number
of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its
implications.
Background
Swedish women have experienced an almost epidemic
increase in body weight in recent decades, as have
women in western societies in general [1,2]. In addition
to the general health complications that are the same
for both sexes, women of fertile age are also more sus-
ceptible to reproductive hazards in connection with
pregnancy and childbirth [3].Obese women have an
increased risk of several complications during pregnancy
and delivery [4,5]. There is also an increased risk for
neonatal complications [4-6]. Overweight and obese
pregnant women are also at increased risk for instru-
mental deliveries employing, for example, forceps,
vacuum extraction or caesarean section (CS), which are
procedures not completely free of risk even among
women of a normal body constitution [3,5-7]. The risks
connected with instrumental deliveries include perineal
tears, thromboembolic complications, wound ruptures
and infections. Furthermore, a CS will lead to a higher
proportion of uterine scars that may cause trouble in
the following pregnancy.
During the last 20 years the rate of CS has increased
in Sweden as well as in many other countries [8]. The
proportion of pregnant women suffering from a high
BMI has also increased rapidly during the same time
period. It would therefore be of interest to study how
and in what ways these two changes might be related to
each other. The Swedish Medical birth register
maintained by the Board of Health and Welfare covers
pregnancy data on each mother’s weight only since
* Correspondence: Gunilla.Sydsjo@lio.se
Division of Obstetrics and Gynaecology, Department of Clinical and
Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-
581 85 Linköping, Sweden
Sydsjö et al. Reproductive Health 2010, 7:18
http://www.reproductive-health-journal.com/content/7/1/18
© 2010 Sydsjö et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
1992. To incorporate other parameters of possible
importance for delivery outcome, parameters that have
not been available in the Swedish birth register until
recently, we decided to utilize a manually compiled
database on pregnancy and delivery with data from 1978
until 2001 [9]. We hypothesised, that given that the
same indications to perform an instrumental delivery or
CS were relevant, no substantial increase should be
found over time among pregnant women in three differ-
ent BMI groups.
Methods
Information from an already available database on
women who gave birth at two different Swedish hospi-
tals in 1978, 1986, 1992, 1997 and 2001 was utilized. All
information for the years 1978, 1986, 1992 and 1997
was collected manually. Data from 2001 were extracted
from the computerized file system (Obstetrix®, Siemens).
This particular database was originally collected in order
to study shifts in sickness absence during pregnancy.
These results are published elsewhere [8,9]. The study
years were chosen as they represented shifts in the var-
ious social security benefits introduced in Sweden over
the same time. Swedish antenatal, delivery and neonatal
information are registered in standardised and identical
records. No major changes of the records occurred dur-
ing the study period. The following data were collected:
the pregnant woman’s age, parity, height and weight at
the beginning of the pregnancy. Relevant information
such as smoking habits and occupation were also
extracted. Delivery data such as gestational week at
delivery and mode of delivery were retrieved from the
delivery records.
If any of the required parameters was missing in the
antenatal or delivery records the woman was excluded.
Hence, of the original 4 911 delivered women, 3 798
(77.3%) could be included. BMI was calculated on infor-
mation from the woman’s first visit at the antenatal care
clinic (ACC), which occurs in gestational week 8-10.
Gestational length was calculated by ultrasound for all
women, with the exception of 1978, when date of last
menstrual period still was used.
Ethics
The study was approved by the Human Research Ethics
Committee, Faculty of Health Sciences, Linköping
University.
Statistics
Differences between the three BMI-groups (i.e. < 20, 20-
24.9, and ≥ 25) studied with regard to caesarean sections
and instrumental deliveries during each year of study
(i.e. 1978, 1986, 1992, 1997, and 2001) were tested by
means of the c2 test. In order to be able to adjust for
potentially important background characteristics, multi-
ple logistic regression analysis was used. In these ana-
lyses, caesarean sections and instrumental deliveries
(coded as yes/no) were defined as dependent variables
and BMI-group, parity (no previous children/previous
children), age, smoking habits (yes/no), occupational sta-
tus (gainfully employed/not gainfully employed), and
twinning (yes/no) were defined as independent variables.
We also tested if there were any indications of time-
trends for caesarean sections or instrumental deliveries
within each BMI-group by means of the c2 test for
trend.
Results
Among the 3 798 women studied, 25.5% had a BMI of
25 or more and 17.6% had a BMI less than 20, and the
proportion of overweight women increased by time (c2
test for trend; p < 0.001) (Table 1). Table 1 further
shows that, on average during the time period, 12.5% of
the women studied had been delivered by means of CS
and that 7.2% of the deliveries were classified as instru-
mental (forceps or vacuum extraction). The proportion
of CS also increased over the time period studied (c2
test for trend; p < 0.001).
There were differences in the proportion of CS among
the women in the different BMI-groups during the years
1992 and 2001 (c2 test; p < 0.001 and 0.003, respec-
tively), see Figure 1. In 1992, the OR for being delivered
by CS was 3.76 (95% CI: 1.82-7.76) among the women
whose BMI was ≥ 25, compared to women with BMI <
20 (p < 0.001), even after adjustments for certain back-
ground characteristics (i.e. parity, age, smoking habits,
occupational status, and twinning). The corresponding
OR and CI were 2.78 (1.33-5.82) during the year 2001
(p = 0.007). Sub-analyses was performed among the
women who gave birth in 1978, 1986, 1992, and 1997,
in which CS were divided into ‘acute’ and ‘elective’,
respectively (data not shown; women who gave birth in
2001 were excluded as we did not have sufficient infor-
mation to further categorize them). The only difference
found between BMI-groups in these sub-analyses was
among women who gave birth in 1992, at which point
women who’s BMI was ≥ 25 were more likely than
others to have an elective CS (c2 test; p = 0.007). In Fig-
ure 1, no significant time-trends for CS within each
BMI-group were found for the time period studied (i.e.
1978-2001); the most pronounced indication was found
for women whose BMI was ≥ 25 (c2 test for trend; p =
0.081).
Figure 2 displays the proportion of instrumental deliv-
eries in relation to BMI-group and year of study.
The c2 tests revealed no differences between BMI-
groups during the years, but when adjustments were
made for background characteristics there was an
Sydsjö et al. Reproductive Health 2010, 7:18
http://www.reproductive-health-journal.com/content/7/1/18
Page 2 of 5
overrepresentation of instrumental deliveries among
women whose BMI was ≥ 25, compared to those with a
BMI < 20, during the year 1978; OR = 4.01 (95% CI:
1.53-10.50), p = 0.005. In Figure 2, no time-trends for
instrumental deliveries were evident within each BMI-
group between 1978 and 2001. However, when the first
study year (i.e. 1978) was excluded from the analyses, a
positive trend was found among women with a BMI of
≥ 25 (c2 test for trend; p = 0.004).
In Figure 3, the percentage of women with BMI ≥ 25
among those delivered by means of CS or instrumental
deliveries, respectively, are displayed. The proportion of
women with BMI ≥ 25 in both groups increased quite
dramatically from 1978 to 2001 (c2 test for trend; p <
0.001 for both CS and instrumental deliveries).
Table 2 shows the mean birth weight in relation to BMI
and year of study among women delivered by means of
CS. Differences were found between the three BMI-groups
during the years 1978 and 2001 (F-test; p = 0.022 and
0.015, respectively). There were also significant differences
over time within each BMI-group concerning birth weight,
mainly evident as a decrease between 1997 and 2001
(F-test; p = 0.005, p = 0.004, and p = 0.003 for BMI < 20,
20-24.9, and ≥ 25, respectively).
Discussion
In this study we did not find any significant time-trends
for CS or instrumental deliveries within each BMI-
group from 1978 to 2001. However, from 1986 on, it
seems as if women with a BMI of ≥ 25 were delivered
with an instrumental delivery to a greater extent than
prior to that time.
The increased risk of CS and instrumental deliveries
in overweight and obese women is well known [5]. The
results from the present study, however, points out that
the relative proportion of overweight and obese women
in the CS- and instrumental delivery groups has
increased. In 1978, 11.1% of all women were overweight
or obese and the relative proportion of these women in
the CS and instrumental delivery groups were 11% and
18% respectively. In 2001, 38.3% of all women were at
least overweight whereas these women constituted 49%
and 42% of the CS and instrumental deliveries
respectively.
Table 1 Characteristics of the study population
Year of study Total
1978 1986 1992 1997 2001
No. of studied women 595 (656) 654 (671) 925 (1178) 604 (863) 1 020 (1543) 3 798 (4911)
Categorized BMI
< 20 186 (31.3%) 153 (23.4%) 152 (16.4%) 75 (12.4%) 103 (10.1%) 669 (17.6%)
20-24.9 343 (57.6%) 416 (63.6%) 542 (58.6%) 334 (55.3%) 526 (51.6%) 2 161 (56.9%)
≥ 25 66 (11.1%) 85 (13.0%) 231 (25.0%) 195 (32.3%) 391 (38.3%) 968 (25.5%)
No. of Cesarean sections 54 (9.1%) 74 (11.3%) 118 (12.8%) 58 (9.6%) 171 (16.8%) 475 (12.5%)
No. of instrumental deliveries 54 (9.1%) 44 (6.7%) 33 (3.6%) 48 (7.9%) 94 (9.2%) 273 (7.2%)
Figure 1 Percentage of Caesarean sections in relation to BMI
and year of study.
Figure 2 Percentage of instrumental deliveries in relation to
BMI and year of study.
Sydsjö et al. Reproductive Health 2010, 7:18
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Page 3 of 5
Overall the proportion of women with BMI ≥ 25
delivered by means of CS or instrumental deliveries
increased quite dramatically from 1978 to 2001, which
probably is explained by the general increase of over-
weight and obesity in the population [1,2,10]. The tem-
porary decline in CS incidence in 1997 is most probably
explained by local intervention programs to break the
trend of increasing CS rates. Apparently, these programs
did not have any long lasting effects. We also found that
the mean birth weight in relation to BMI and year of
study among women delivered by means of CS
decreased. This decrease was evident mainly after 1997
and might be explained by wider indications, new tech-
nologies have been introduced in order to identify
foetuses at risk during delivery and an increased readi-
ness to perform a CS over time [11]. Although this clin-
ical study material is rather small, it contains valuable
information, which would have been difficult to obtain
through national databases or other sources.
It is also a strength of the study that the material
was collected through prospectively gathered informa-
tion in standardised antenatal and delivery records and
not by maternal recall. In this study, the BMI is calcu-
lated from information on weight and height as
measured at the first visit to antenatal care clinic, in
gestational week 8-10 week which adds to the credibil-
ity of the study. The dropout was evenly distributed
for all years of the study and was not considered of
importance for the result as it is believed to depend on
underreporting in the standardised file. Except from
BMI, gestational weight gain has been identified as
another aspect which might increase the risk for CS
irrespective of BMI [12].
Conclusion
In conclusion, it is evident that overweight and obese
pregnant women constitute a rapidly growing propor-
tion of the total amount of CS and instrumental deliv-
eries. Planning and allocation of health resources must
be adjusted to this fact and its implications.
Figure 3 Percentage of women with BMI ≥ 25 among women delivered by means of Caesarean section or instrumental deliveries
during the study period.
Table 2 Mean birth weight in relation to BMI and year of
study among women delivered by means of Caesarean
section
BMI < 20 BMI 20-24.9 BMI > = 25
Mean N Mean N Mean N
1978 2905 14 332 34 3916 6
1986 3120 15 3047 42 3320 16
1992 3293 9 3407 61 3523 45
1997 3110 6 3533 28 3629 23
2001 1994 10 2981 77 3047 84
5 children’s birth weight was uncertain therefore excluded.
Sydsjö et al. Reproductive Health 2010, 7:18
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Page 4 of 5
Acknowledgements
Funding
This study was supported by grants from The Health Research Council in the
southeast of Sweden.
Ethical Approval
The study was approved by the Human Research Ethics Committee, Faculty
of Health Sciences, Linköping University.
Authors’ contributions
GS designed the study, data collection, analysis of data, preparation of the
manuscript, AS research idea and design, analyses of data, preparation of
the manuscript, JB analysis of data, preparation of the manuscript, AJ
analysis of data, preparation of the manuscript. All authors read and
approved the final manuscript.
Competing interests
The authors declare that they have no completing interests.
Received: 22 April 2010 Accepted: 22 July 2010 Published: 22 July 2010
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Cite this article as: Sydsjö et al.: Trends in caesarean section and
instrumental deliveries in relation to Body Mass Index: a clinical survey
during 1978 - 2001. Reproductive Health 2010 7:18.
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A: The importance of maternal BMI on infant’s birth weight in four BMI groups for the period 1978-2001. Acta Obstet Gynecol Scand

Acta Obstet Gynecol Scand

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Effects of gestational weight gain and body mass index on obstetric outcome in Sweden. Int J Gynaecol Obstet

FASTER Research Consortium: Obesity, obstetric complications and cesarean delivery rate– a population-based screening study.

JC: The effect of the increasing prevalence of maternal obesity on perinatal morbidity.

MS: Prepregnancy weight and the risk of adverse pregnancy outcomes.

Outcome of pregnancy in a woman with an increased body mass index. BJOG

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Sydsjö G: Trends in body mass index during early pregnancy in Swedish women 1978-2001. Public Health

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http://doaj.org/search?source=%7B%22query%22%3A%7B%22bool%22%3A%7B%22must%22%3A%5B%7B%22term%22%3A%7B%22id%22%3A%223b8b0c502dae4adea36e0350c790f33d%22%7D%7D%5D%7D%7D%7D

Trends in caesarean section and instrumental deliveries in relation to Body Mass Index: a clinical survey during 1978 - 2001

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