epidemiology of infertility scotland
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ORIGINAL ARTICLE Infertility
The epidemiology of infertility
in the North East of Scotland
S. Bhattacharya 1,4, M. Porter 1, E. Amalraj2, A. Templeton1,
M. Hamilton1, A.J. Lee2, and J.J. Kurinczuk 3
1Obstetrics and Gynaecology, University of Aberdeen, Aberdeen Maternity Hospital, Foresterhill, Aberdeen AB25 2ZD, UK 2The Centre of
Academic Primary Care, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK 3National Perinatal Epidemiology Unit, University of
Oxford Old Road Campus, Headington, Oxford OX3 7LF, UK
4Correspondence address: Tel: 01224 550590; Fax: 01224 559948; E-mail: [email protected]
background: There is a perception that the prevalence of infertility is on the rise. This study aimed to determine the current preva-
lence of infertility in a defined geographical population, ascertain changes in self-reported infertility over time and identify risk factors associ-
ated with infertility.
methods: A postal questionnaire survey of a random population-based sample of women aged 31–50 years was performed in the
Grampian region of Scotland. Questions addressed the following areas: pregnancy history, length of time taken to become pregnant each
time, whether medical advice had been sought and self-reported exposure to factors associated with infertility.
results: Among 4466 women who responded, 400 (9.0%) [95% CI 8.1, 9.8] had chosen not to have children. Of the remaining 4066
women, 3283 (80.7%) [95% CI 79.5, 82.0] reported no difficulties in having children and the remaining 783 (19.3%) [95% CI 18.1, 20.5] had
experienced infertility, defined as having difficulty in becoming pregnant for more than 12 months and/or seeking medical advice. In total 398
(9.8%) [95% CI 8.9, 10.7] women had primary infertility, 285 (7.0%) [95% CI 6.2, 7.8] had secondary infertility, 100 (2.5%) [95% CI 2.0, 2.9]
had primary as well as secondary infertility. A total of 342 (68.7%) and 208 (73.0%) women with primary and secondary infertility, respect-
ively, sought medical advice and 202 (59.1%) and 118 (56.7%) women in each group subsequently conceived. History of pelvic surgery, Chla-
mydial infection, endometriosis, chemotherapy, long-term health problems and obesity were associated with infertility. In comparison with a
similar survey of women aged 46–50 from the same geographical area, the prevalence of both primary infertility ( .24 months) [70/1081,
(6.5%) versus 68/710 (9.6%) P ¼ 0.02] and secondary infertility [29/1081 (2.7%) versus 40/710 (5.6%) P ¼ 0.002] were significantly lower.
conclusions: Nearly one in five women attempting conception sampled in this study experienced infertility, although over half of them
eventually conceived. Fertility problems were associated with endometriosis, Chlamydia trachomatis infection and pelvic surgery, as well as
obesity, chemotherapy and some long-term chronic medical conditions. There is no evidence of an increase in the prevalence of infertility
in this population over the past 20 years.
Key words: prevalence / risk factors / subfertility / epidemiology / infertility
Introduction
Infertility is defined as the inability to conceive following 12–24
months of exposure to pregnancy (Templeton et al . 1990). In 2002,
over 186 million women worldwide experienced problems conceiving.
This figure is higher than previous estimates, suggesting a global rise in
the prevalence of infertility (Farley, 1986, Rutstein and Shah, 2004). At
the turn of the last century projections of infertility in the United States
indicated a sharp upward trend over the next two decades (Stephen
and Chandra, 1998) while data from Europe suggested that increasing
numbers of couples were seeking assisted reproduction (Lutz and
Qiang, 2002). There is widespread concern about the effect of con-
tributory factors such as sexually transmitted infections like
Chlamydia trachomatis (Pal and Santoro, 2003; Karinen et al ., 2004),
deterioration in semen quality (Irvine et al ., 1996; Karinen et al .,
2004) and age-related decline in ovarian function in women
(Gosden and Rutherford, 1995; Dunson et al ., 2004) who choose
to postpone childbirth (Bhattacharya et al ., 2006; Goto et al ., 2006).
Results from existing studies suggest that the lifetime prevalence
of infertility is between 6.6% (Rostad et al ., 2006) and 32.6%
(Marchbanks et al ., 1989). This wide variation could reflect actual
population-based differences, but is more likely to be due to differ-
ences in defining and measuring infertility (Rachootin and Olsen,
1982; Page, 1989; Greenhall and Vessey,1990; Templeton et al .,
1991; Gunnell and Ewings, 1994; Schmidt and Munster, 1995;
Philippov et al ., 1998; Wyshak, 2001; Gnoth et al ., 2003; King,
& The Author 2009. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
For Permissions, please email: [email protected]
Human Reproduction, Vol.24, No.12 pp. 3096–3107, 2009
Advanced Access publication on August 14, 2009 doi:10.1093/humrep/dep287
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2003; Rostad et al ., 2006). Few recent studies have been based on
self-reported data from a representative population. Fewer still have
covered the full spectrum of reproductive experience including miscar-
riages and ectopic pregnancies (Maconochie et al ., 2004) or addressed
secular trends (Stephen and Chandra, 1998) in the prevalence of infer-
tility. A recent reproductive survey in the UK (Oakley et al ., 2008) has
reported that 2.4% women aged 40–55 had never been pregnant
(despite having tried) and 16% of them had consulted a doctor
about this. Despite a large sample size of 6580 women, this study
was not designed to provide data on how long women had tried for
a pregnancy or to examine the association between lifestyle and
medical factors and infertility.
A population-based study on the prevalence of infertility was con-
ducted in Grampian in 1988 (Templeton et al ., 1991). The stable
population in the north-east of Scotland, coupled with access to the
tools used in this previous postal survey offered the unique opportu-
nity of performing a study on the epidemiology of infertility in the same
geographical area at the present time. In the present study we aimed
to establish the current prevalence of infertility, ascertain changes in
self-reported infertility over time and to identify risk factors associated
with infertility.
MethodsA cross-sectional study was undertaken. Data were collected by means of
a population-based postal survey of women aged 31–50 years living in
Grampian, Scotland in 2007. Women were identified from the Community
Health Index (CHI) which lists everyone who is registered with a general
practitioner in Scotland. As all individuals in the UK are expected to reg-
ister with a general practitioner, CHI effectively covers all women living in
Scotland who access any form of primary, secondary or tertiary health
care or screening (such as cervical screening).The CHI number for an indi-
vidual contains date of birth, a number to represent sex and a personal
identifier. A randomly selected sample of 9000 women was sent an invita-
tion to participate from the office of the Director of Public Health (DPH)
along with an information sheet, a self-completion questionnaire and reply-
paid envelope. Responses were logged and reminder letters and a second
complete mailing were sent to non-responders (by the DPH Office) to
maximize the response. Questionnaires were completed anonymously
and the identities of the respondents were not known to the researchers.
The questionnaire was structured and largely pre-coded for ease of data
entry, and incorporated identical questions from the previous study
(Templeton et al ., 1991) conducted in this area in 1988 as well as some
new questions on lifestyle factors. Questions addressed the following
domains:
Reproductive history : Current and past use of contraception, pregnancy
history including miscarriages, terminations and ectopic pregnancies,
births, time to each pregnancy and whether medical advice was sought
for fertility problems.
Medical and lifestyle information: General health, medical history perti-
nent to fertility problems, current levels of smoking, drinking and exercise,
current height and current weight, and an assessment of quality of life using
the Euroquol scale (Brochs and EuroQOL Group., 1996).
Demographic information: Age, marital status, educational level, own
occupation and partner’s occupation. Deprivation was assessed by
linkage of the responder postcodes to The Scottish Index of Multiple
Deprivation (SIMD, 2006) which is a small area statistic of deprivation
derived from 37 indicators across the seven domains of: income, employ-
ment, health, education skills and training, geographic access to services,
housing and crime. The first quintile corresponds to the least deprived
and the fifth quintile the most deprived zones. Age and SIMD 2006 quintile
data were available from the CHI for the non-responders.
We assumed a 60% response after two mailings to 9000 women which
would generate 5400 completed questionnaires. Taking the prevalence of
primary and secondary infertility to each be in the range of 6– 8%
(Templeton et al ., 1990) 5400 responses would enable us to estimate
the current prevalence of infertility with a 95% confidence interval of
+1%. Under these assumptions this sample size would yield 700
women with infertility (either primary or secondary infertility or both)who would form the basis of a nested, unmatched, case–control analysis
to explore factors associated with infertility. With the estimated 700 cases
this analysis would have 80% power to detect, at the 5% level of statistical
significance, an odds ratio of 1.5 or greater for exposures with a
prevalence in the controls ranging from 15 to 70% and an odds ratio of
2.0 or greater for exposures ranging from 5 to 90%.
The data from the completed questionnaires were entered into a study-
specific database by trained data entry staff, and checked, cleaned and ana-
lysed using SPSS (Statistical Package for the Social Sciences; IL, USA).
To enable comparison with published data we defined infertility in three
different ways: unsuccessful attempted conception for 12 months or
longer (in line with current clinical practice); unsuccessful attempted con-
ception for 24 months or longer (for comparison with data from the 1988
survey); (Templeton et al ., 1990) and unsuccessful attempted conceptionfor 12 months or longer and/or had sought medical help with conception
(Schmidt et al ., 1995). The latter definition was derived to ensure the
inclusion of women with a prior history of successful fertility treatment
who had sought a second course of treatment without attempting spon-
taneous conception for 12 months or longer and older women who, in
line with current clinical practice, may be referred early for treatment,
that is before attempting conception for 12 months. Primary infertility
refers to problems with conceiving a first pregnancy and secondary infer-
tility to conception problems in any subsequent pregnancy. Data are
reported for the whole cohort (31–50 years) and for age groups 36–
40 years and 46–50 years to correspond with the results reported by
Templeton et al . (1990).
Ninety-five per cent confidence intervals (95% CIs) of prevalence esti-
mates were derived. Basic descriptors were compared across infertilitygroups by univariate analyses using the chi-square test, independent
t -test and Mann–Whitney U -test as appropriate. Unconditional logistic
regression modelling was used to explore the independent relationship
between demographic, medical and lifestyle factors, and infertility status.
Variables considered as potential confounders were those which had
shown a univariate association at P , 0.10. A forward stepwise procedure
was employed and a final parsimonious model was derived by the removal
of factors which did not significantly contribute to the fit of the model using
a P -value of less than or equal to 0.05. The study was approved by the
North of Scotland Research Ethics Service.
ResultsA total of 4522 women completed and returned the questionnaire, a
response of 50.2% (Table I). Responders were similar in mean (SD)
age to overall study sample [40.9 (5.6) years versus 41.0 (5.5)
years, respectively] but were less likely to live in a socially deprived
area: [12.6 versus 17.2% in SIMD 2006 categories 4 and 5,
respectively].
The mean (SD) number of children among responders was 1.75
(1.31). Of the 4522 women who responded to the questionnaire,
56 had not yet tested their fertility, and were excluded from further
analysis. These women were significantly younger than those included
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in the analysis (P , 0.001); 52% were 35, 23% were 36–40, 11%
were 41–45 and 14% were 46–50 years of age. For women whose
fertility had been tested, the corresponding percentages were 21,27, 27 and 26% respectively.
Among 4466 women, 400 women (9%) specifically reported avoid-
ing pregnancy and were voluntarily childless, and this was the case for
5.8% (n ¼ 67) of women aged 46–50 years. Based on duration alone,
82.5% (n ¼ 3356) of the cohort of 4066 women reported no difficulty
in becoming pregnant using the 12 month cut-off, and 90.9% ( n ¼
3681) reported no difficulty when the 24 month cut-off was applied
(Table II).
Among those women who attempted conception (n ¼ 4066)
the prevalence of primary infertility alone was 10.5% based on the
12 month time to conception cut-off and 5.9% based on the
24 month cut-off. Secondary infertility alone affected 5.3% of
women using the 12 month cut-off and 2.9% using the 24 monthfigure. A small number of women experienced both primary and
secondary infertility: 1.7 and 0.3% according to the 12 month and
24 month cut-offs, respectively. Overall, 17.5% of women experi-
enced difficulty conceiving at some stage in their life when the
12 month cut-off was applied and 9.1% reported the same experience
when the 24 month definition was used. There was no evidence of a
significant trend in the prevalence of infertility across the different
age groups of women when the definition was based on duration of
infertility alone. The prevalence of primary unresolved infertility
(women with no pregnancies at all despite trying) was 4.0% in the
entire cohort and 4.1% in women aged 46–50 years.
Using the definition of infertility based on both duration and/or
having sought medical help with conception, the overall prevalence
estimates of infertility increased for both the time to conception
cut-offs to 19.3% for the 12 month time to conception cut-off and
11.8% for the 24 month cut-off (Table III). Using the time to con-
ception cut-off of 12 and 24 months, respectively in combination
with seeking medical help resulted in prevalence estimates of: 9.8
and 5.7% for primary infertility alone; 7.0 and 5.2% for secondary
infertility alone; and 2.5 and 0.9% for both primary and secondary
infertility. There was no increase in the prevalence of infertility with
increasing age groups when the definition was based on a duration
of either 12 months or .24 months as well as health seeking
behaviour. Overall 4.1% of women who attempted conception
never conceived a first pregnancy and this was the case for 4.2% of
women aged 46–50 years.
Of all those with infertility, 145 (73.6%) women aged between 36
and 40 years and 145 (67.1%) between 46 and 50 years had sought
medical advice about their inability to conceive (P ¼ 0.15). This
included a total of 342 (68.7%) and 208 (73.0%) women with
primary and secondary infertility, respectively. Slightly, although not
significantly, more women aged 36–40 years with primary infertility
had sought medical help in comparison with women aged 46–50
years (71.0 versus 64.5%, respectively; P ¼ 0.25). The corresponding
proportions for secondary infertility were 78.8 and 71.8% ( P ¼ 0.33).
Among those who sought help, 202 (59.1%) women with primary
infertility and 118 (56.7%) with secondary infertility ultimately con-
ceived. However, we were unable to confirm from the questions
we asked on this subject (which were the same asked in the previous
study) if these pregnancies occurred with or without active treatment.
In comparison, spontaneous pregnancies occurred in 88 (56.4%)
women with primary and 72 (93.5%) with secondary infertility.
Overall, 58.2% (290/498) of women with primary infertility eventually
conceived, as did 66.7% (190/285) of those with secondary infertility(Table III). The outcomes of all the pregnancies of the infertile and
fertile groups are given in Table IV. Women who experienced inferti-
lity were significantly more likely to have had a spontaneous pregnancy
loss, an ectopic pregnancy and a stillbirth but less likely to have had a
legal termination of pregnancy. Whilst the proportion of live births was
similar for the primary infertility and fertile groups the proportion was
significantly lower in the secondary infertility group.
The commonest self-reported causes of infertility were ovulation
problems, sperm quality problems and unexplained infertility
(Table V). Some women reported more than one cause of their infer-
tility: 129 (77.2%) women reported one, 29 (16.4%) reported two,
and nine women (5.1%) reported three causal factors contributing
to their primary infertility; and 124 (82.1%) women reported one,21 (13.9%) reported two, and six (4.0%) reported three factors in
relation to their secondary infertility.
The relationship between demographic, medical and lifestyle factors
and ever having experienced infertility (primary, secondary or both)
were explored (Table VI). Women who had experienced infertility
were more likely (P , 0.05) to be obese and to report a lower
quality of life score on the Euroquol scale; other lifestyle and demo-
graphic indicators were not significantly different between the
groups. In contrast, as regards medical and reproductive indicators,
the infertile group was significantly more likely to report a history of
tubal surgery, other pelvic surgery, appendicectomy and/or endome-
triosis; a history of Chlamydial infection; a history of chemotherapy
and long-term health problems. They were significantly less likely to
report intrauterine contraceptive device (IUCD), use of surgical ster-
ilization (either of themselves or their partners).
Educational status, previous pelvic surgery or endometriosis, che-
motherapy, Chlamydial infection, long-term health problems, pack
years of cigarette smoking and BMI were included in the logistic
regression model. We did not include male and female sterilization vari-
ables in the model because these interventions are more commonly
offered to couples who have completed their family than they are a
cause of infertility. For a similar reason we did not include IUCD use
in the model. Although potentially associated with infertility, an IUCD
........................................................................................
Table I Response to postal questionnaires
Outcome First
mailing
April–May
2007, N
Second
mailing
June –July
2007, N
Total, N
(%)
Questionnaire
completed
3316 1206 4522 (50.2)
Refused to
participate
950 256 1206 (13.4)
Questionnaire sent
to wrong address
and ineligible
subjects
92 29 121 (1.4)
Did not respond 4642 3151 3151 (35.0)
Total mailed 9000 4642 9000 (100.0)
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Table II Prevalence of infertility and eventual conception based on duration of attempting conception only
Duration of at least 12 months Duration of at least 24 months
Entire cohort, age 31–
50 years, n 5 4466a,f
,N (%)
Age 31–
35 years,n5 922,
N (%)
Age 36–
40 years,n 5 1189,
N (%)
Age 41–
45 years,n 5 1206,
N (%)
Age 46–
50 years,n 5 1149,
N (%)
Entire cohort, age 31–
50 years, n 5 4449b,f
N (%)
Age 31–
35 years,n5 917,
N (%)
Primary
infertility
426 (10.5) [9.5–11.4]d 93 (12.2) 110 (10.0) 108 (9.6) 115 (10.6) 239 (5.9) [5.2–6.6]d 49 (6.5)
Never
conceived
162 (4.0) 37 (4.9) 37 (3.4) 44 (3.9) 44 (4.1) 136 (3.4) 27 (3.6)
Eventually
conceived
264 (6.5) 56 (7.4) 73 (6.7) 64 (5.7) 71 (6.6) 103 (2.5) 22 (2.9)
Primary and
secondary
infertility
67 (1.7) [1.3–2.0]d 11 (1.5) 20 (1.8) 14 (1.2) 22 (2.0) 13 (0.3) [0.2 –0.5]d 1 (0.1)
Not pregnant 8 (0.2) 2 (0.3) 5 (0.5) 1 (0.1) 0 (0.0) 2 (0.05) 0 (0.0)
Becamepregnant
59 (1.6) 9 (1.2) 15 (1.4) 13 (1.2) 22 (2.0) 11 (0.3) 1 (0.1)
Secondary
infertility
217 (5.3) [4.7–6.0]d 45 (5.9) 50 (4.6) 67 (6.0) 55 (5.1) 116 (2.9) [2.4 – 3.4]d 22 (2.9)
Not pregnant 27 (0.7) 14 (1.8) 8 (0.7) 1 (0.1) 4 (0.4) 25 (0.6) 12 (1.6)
Became
pregnant
190 (4.7) 31 (4.1) 42 (3.8) 66 (5.9) 51 (4.7) 91 (2.3) 10 (1.3)
Total
infertility c710 (17.5) [16.3–18.6]d 149 (19.6) 180 (16.4) 189 (16.8) 192 (17.7) 368 (9.1) [8.2–10.0]d 72 (9.5)
No infertility 3356 (82.5) [81.4– 83.7]d 612 (80.4) 917 (83.6) 937 (83.2) 890 (82.3) 3681 (90.9) [90.0–91.8]d 684 (90.5)
Overall
Totale4066 761 1097 1126 1082 4049 756
Voluntary
childlessness
400 (9.0) [8.1–9.8]d 161 (17.5) 92 (7.7) 80 (6.6) 67 (5.8) 400 (9.0) [8.2–9.8]d 161 (17.6)
aExcludes 56 and b73 women with untested fertility.cTotal of primary, secondary and primary as well as secondary.d95% Confidence intervals for prevalence.eOverall Total includes Total infertility as well as No infertility.f Includes Total infertility, No infertility as well as Voluntary childlessness.
b y g u e s t o n F e b r u a r y 9 , 2 0 1 1 h u m r e p . o x f o r d j o u r n a l s . o r g D o w n l o a d e d f r o m
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is also a common form of contraception for women who have
completed their child bearing. The mutually adjusted results are given
in Table VII. Pelvic conditions, chemotherapy, Chlamydial infection,
long-term health problems and obesity were each independently
associated with an increase in the odds of infertility.
Comparison with previous Grampian data Table VIII shows that in comparison with the previous study
(Templeton et al ., 1990) on the same geographical population, the
current proportion of women aged 46–50 with a history of infertility
of 24 months or longer duration was significantly lower [99/1081,
(9.2%) versus 108/710 (15.2%) than in the past (P , 0.001).
Discussion
Our results suggest that nearly one in five women of reproductive age
attempting conception experience infertility; one in 25 women at the
end of their reproductive years never conceived a desired pregnancy;
and 1 in 11 is childless by choice. There is no evidence of an increase
in the proportion of women with infertility over the past two decades.Factors independently associated with infertility include current
obesity, a history of long-term health problems, chemotherapy,
pelvic problems (endometriosis and surgery) and Chlamydial infection.
This study follows on from an earlier one (Templeton et al ., 1990)
in the same geographical area and used identical questions pertaining
to trying for and time to achieve each pregnancy in a large random
sample of women. In addition, we are able to comment on the associ-
ation of common lifestyle factors and medical conditions with inferti-
lity. As measuring prevalence of infertility is always contentious
(Gnoth et al ., 2005), we have used a number of alternative definitions
for this condition. Obtaining current demographic and lifestyle data
avoided any bias due to self-reporting of historical information,
although we acknowledge the limitations of using these data as aproxy for historical information.
One of the potential shortcomings of this project is the response
rate of just over 50%. This is lower than our previous study
(Templeton et al ., 1990, 1991) and others conducted more than a
decade ago (Buckett and Bentick, 1997) but higher than a recent
reproductive survey in the UK (Oakley et al ., 2008) which had a
response rate of 46%. We attempted to minimize non-response by
sending two mailings of the questionnaires, but unlike some of the pre-
vious studies (Templeton et al ., 1990; Buckett and Bentick, 1997)
which had a response rate of 85.7 and 85%, respectively, were
unable to contact non-responders by telephone which would have
compromised anonymity. In accordance with previous reports
(Schmidt and Munster, 1995) and in common with postal surveys in
general we found differences in socio-economic position between
responders and non-responders, although they did not differ in their
age distributions. This socio-economic disparity may have led to a
slight under estimate of the true prevalence of infertility. The profile
of our populations of responders was similar to that of participants
in the Scottish Health Survey (The Scottish Government) for
women of the same age. Responders who smoked reported similar
levels of mean daily cigarette intake (13.7 versus 14.9 in the Health
Survey), those who drank reported a similar mean weekly alcohol
intake (7.0 versus 6.5 units) and overall 36.9% of responders versus
.............................................................................................................................................................................................
Table IV Outcomes of all pregnancies in fertile and infertile* women
Women with primary
infertility † (n 5 498)
N (%)
Women with secondary
infertility (n5 285)
N (%)
Women with no
infertility (n 5 3283)
N (%)
P -value (across all
three groups)
Births 598 (79.8) 555 (74.1) 6778 (78.9) ,0.001
Stillbirth 9 (1.2) 12 (1.6) 52 (0.6)
Spontaneous miscarriages 110 (14.7) 167 (22.3) 1013 (11.8)
Ectopic pregnancies 11 (1.5) 6 (0.8) 66 (0.8)
Terminations 19 (2.5) 7 (0.9) 673 (7.8)
Molar pregnancies 2 (0.3) 2 (0.3) 10 (0.1)
Total pregnancies 749 (100) 749 (100) 8592 (100)
Molar pregnancies were combined with terminations for applying chi-square test.
*Unsuccessful attempted conception for 12 months or longer and/or had sought medical help with conception.†Includes women with both primary and secondary infertility.
........................................................................................
Table V Self-reported cause of infertility amongst
women who reported a diagnosis*
Diagnosis** Primary
infertile group
(n 5 167)
N (%)
Secondary
infertile group
(n5 151)
N (%)
P -value
Ovulation
problems
54 (32.3) 35 (23.2) 0.069
Sperm quality
problems
49 (29.3) 36 (23.8) 0.268
Blocked
fallopian tubes
20 (12) 21 (13.9) 0.607
Unexplained
infertility
49 (29.3) 45 (29.8) 0.928
Endometriosis 19 (10.7) 15 (10) 0.677
Others 23 (13.8) 32 (21.2) 0.081
*Unsuccessful attempted conception for 12 months or longer and/or had sought
medical help with conception.
**Women have reported more than one diagnosis.
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Table VI Demographic, lifestyle and medical factors in women with and without experience of infertility*
Factor Category Experienced infertility*
(n 5 783)
N (%)
No infertility*
(n5 3283)
N (%)
P -value
Demographic factors
†Age 41.11 (5.6) 41.19 (5.4) 0.703
Currently employed Yes 613 (78.5) 2654 (81.0) 0.129
Social deprivation (SIMDEC,
2006 quintiles)
1-Least deprived 271 (34.6) 1158 (35.3) 0.491
2 239 (30.5) 992 (30.2)
3 166 (21.1) 738 (22.5)
4 73 (9.3) 292 (8.9)
5-Most deprived 34 (4.3) 103 (3.1)
Partner in employment Yes 676 (88.8) 2790 (87) 0.39
Education None 68 (8.7) 242 (7.4) 0.078
High School 295 (37.9) 1369 (42.1)
College-University 416 (53.4) 1643 (50.5)
Marital status Single 38 (4.9) 135 (4.1) 0.313
Separated/Divorced/Widow 78 (10.0) 389 (11.9)
Living with partner 83 (10.6) 376 (11.5)
Married 583 (74.6) 2376 (72.5)
Own occupation Managerial/Professional 152 (25.2) 587 (22.4) 0.318
Intermediate 241 (39.9) 1068 (40.7)
Routine & Manual occupation 211 (34.9) 969 (36.9)
Partners’ occupation Managerial/Professional 230 (35.1) 1061 (39.0%) 0.115
Intermediate 133 (20.3) 480 (17.6)
Routine & Manual Occupation 293 (44.7) 1183 (43.4)
Medical factors
IUCD use Yes 159 (20.4) 814 (24.9) 0.009
Tubal sterilization Yes 71 (9.2) 481 (14.9) 0.001
Partner sterilized Yes 172 (26.4) 1001 (34.8) 0.001
Past history of any of the
following:
Yes 231 (29.5) 610 (18.6) 0.001
Tubal surgery
Pelvic surgery
Appendicectomy
Endometriosis
Chemotherapy Yes 12 (1.5) 21 (0.6) 0.023
Past Chlamydial infection Yes 45 (5.7) 116 (3.5) 0.006
Long-term health problems** Yes 160 (20.5) 493 (15.1) 0.001
Lifestyle factors
Body mass index ,20 (underweight) 36 (4.6) 198 (6.3) 0.003
20–24.99 (normal weight) 334 (44.1) 1513 (48.2)
25–29.00 (over weight) 220 (29.0) 896 (28.5)
30 (obese) 168 (22.2) 533 (17.0)
Smoking status Current or ex-smoker 318 (41.5) 1315 (41.2) 0.916
Never smoked 449 (58.5) 1879 (58.8)
†Cig/day 15 (10–20) 12 (10– 20) 0.166
Alcohol use Within the last 7 days 537 (68.8) 2288 (69.8) 0.616
†Units consumed per week 5 (3– 10) 6 (3–9) 0.873
Strenuous exercise Exercise .1 h/week 262 (33.5) 1037 (31.6) 0.449
Exercise 0.25 to 1 h/week 186 (23.8) 762 (23.2)
No Exercise 335 (42.8) 1484 (45.2)
Moderate exercise .2 h/week 30 (3.8) 145 (4.4) 0.697
1–2 h/week 268 (34.2) 1075 (32.7)
0.25 to 1 h/week 313 (40.0) 1364 (41.5)
None 172 (22.0) 699 (21.3)
Continued
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33.0% in the Health Survey reported taking 30 min of moderate exer-
cise per week. Furthermore the average family size of 1.75 reported
by responders is consistent with current national figures for Scotland
(General Register Office for Scotland, 2007). National surveys such
as the Scottish Health Survey are unlikely to attract a 100% response
or be completely free of bias. Thus, although the profile of responders
in our study is similar to that of those in the Scottish Health Survey we
acknowledge that this does not guarantee the fact that we have
obtained responses from a representative sample of the population.
Our current estimate of 4.1% for the prevalence of primary unre-
solved infertility in women aged 46–50 was very similar to results
from the same area 20 years ago (Templeton et al ., 1990) and com-
parable to the 2.7– 4.5% prevalence rate quoted in a review of the
.............................................................................................................................................................................................
TableVI Continued
Factor Category Experienced infertility*
(n5 783)
N (%)
No infertility*
(n 5 3283)
N (%)
P -value
Mild exercise .2 h/week 35 (4.5) 147 (4.5) 0.981
1– 2 h/week 321 (41.0) 1332 (40.6)
0.25 to 1 h/week 277 (35.4) 1187 (36.2)None 150 (19.2) 617 (18.8)
Engagement in leisure activity
to sweat
Never/rarely 224 (29.2) 963 (30.1) 0.823
Sometimes 374 (48.7) 1520 (47.5)
Often 170 (22.1) 718 (22.4)
†Quality of life score
(Euroquol)
77.66 (16.9) 79.55 (16.0) 0.005
†Pack years of cigarette
smoking (excluding never
smokers)
10 (5.0–17.3) 10 (4.13–16.0) 0.083
*Unsuccessful attempted conception for 12 months or longer and/or had sought medical help with conception. Percentages based on responses.
**Self-reported long-term health problems include asthma (48), hypothyroidism (14), diabetes (6), arthritis (12), depression (1) and other (17).
†Values are mean (SD) or median (IQR).
........................................................................................
Table VII Health and lifestyle factors associated with
infertility*
Adjusted odds ratio1 (95% CI)
Pelvic problems** 1.8 (1.5 –2.2)
Chemotherapy 2.1 (1.02 –4.5)
Chlamydial infec tion 1.6 (1.1 – 2.3)
Long-term health problemsþþ 1.3 (1.1–1.6)
BMI
20–24.99—normal weight 1.0
,20—under weight 0.9 (0.6 – 1.3)
25 – 29—overweight 1.1 (0.9 – 1.4)
30—obese 1.4 (1.1–1.7)
*Unsuccessful attempted conception for 12 months or longer and/or had sought
medical help.
þOdds ratios mutually adjusted for all the variables reported in the table.
**Tubal surgery, other pelvic surgery, appendicectomy or endometriosis.
11Self-reported long-term health problems include asthma (48), hypothyroidism
(14), diabetes (6), arthritis (12), depression (1) and other (17).
........................................................................................
Table VIII Comparison of infertility prevalence
between the 1988 (Templeton et al ., 1990) and 2007
(present study)
Category 1988 survey, age
46–50 years,
infertility >24
months
(n 5 766)**
N (%)
2007 study, age
46–50 years,
infertility >24
months,
(n 5 1148)**
N (%)
P -value
Primary infertility only 56 (7.9) 67 (6.2) 0.166
Never pregnant 27 (3.8) 42 (3.9)
Ever pregnant 29 (4.1) 25 (2.3)
Primary &
Secondary
infertility
12 (1.7) 3 (0.3) 0.001
Not pregnant 8 (1.1) 0
Became
pregnant
4 (0.6) 3 (0.3)
Secondary
infertility only
40 (5.6) 29 (2.7) 0.001
Not pregnant 17 (2.4) 4 (0.4)
Becamepregnant
23 (3.2) 25 (2.3)
Total
Infertility
108 (15.2) 99 (9.2) ,0.001
No infertility 602 (84.8) 982 (90.8)
Overall Total* 710 1081
Voluntary
Childlessness
56 (7.3) 67 (5.8) 0.197
*Overall Total includes total infertility and No infertility & percentages are based on
overall total.
**Includes total infertility, no infertility and voluntary childlessness.
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literature in 1995 (Schmidt and Munster, 1995). Two recent UK
surveys in 1997 and 2008 both reported a figure of 2.4% (Buckett
and Bentick, 1997; Oakley et al ., 2008).
Some estimates of causes of infertility have been clinic based
(Collins et al ., 1983; Hull et al ., 1985; Katyama et al ., 1989;
Maheshwari et al ., 2008) In contrast, population-based figures are
available (Rachootin and Olsen, 1982; Greenhall and Vessey, 1990;
Thonneau et al ., 1991; Schmidt et al ., 1995; Buckett and Bentick,
1997). Direct comparisons are difficult due to alternative ways of
defining categories and presenting male and female factors
separately (Thonneau et al ., 1992). It is difficult to interpret data on
self-reported causes of infertility as not all couples who experience
problems are fully investigated and responses may be subject to
recall bias. However, despite these limitations, except for a higher
prevalence of male factor infertility, our results are consistent with
those of Buckett and Bentick (1997) one of the more recently
conducted UK population-based studies.
Our results suggest that the overall conception rate in women with
fertility problems was 56.1% which corresponds to previously reported
figures of 38–48% (Collins et al ., 1983; Hull et al ., 1985; Katyama et al .,
1989; Templeton et al ., 1991; Collins et al ., 1994). Of those who con-ceived, 83.8 and 78.9% in women with primary and secondary infertility,
respectively, went on to give birth as compared with 78% in both
groups in the study by Templeton et al . (1991).
Our results confirm previously reported associations between infer-
tility and pelvic-related factors, including pelvic surgery (including
appendicectomy), tubal surgery and sexually transmitted infection
(Thonneau et al ., 1992). We found no significant association
between infertility and current levels of exercise. With the exception
of regular strenuous exercise, which has been linked to hypothalamic
anovulation and amenorrhoea, this has been the finding of other
similar studies (Homan et al ., 2007). We were able to confirm a sig-
nificant association between infertility and current obesity (BMI
30) but not between infertility and other factors reported byHoman et al . (2007) such as current or past smoking, or current
alcohol use. Interpretation of these findings, especially those relating
to smoking, needs to take into account the fact that observed associ-
ations may not be causal, especially given the difficulty of trying to
relate current lifestyle data to events that occurred in the past.
There is ongoing debate about the definition of infertility (Greenhall
and Vessey., 1990; Gnoth et al ., 2005) as well as the appropriate
numerator and denominator used to determine prevalence. Numer-
ators have included lifetime childlessness, lifetime failure to conceive,
lack of conception over a defined period of time (12 or 24 months)
and seeking medical help (Schmidt and Munster, 1995; Oakley et al .,
2008). Denominators have included the whole population of
women of reproductive age, eligible members of the whole population
(i.e. those who have had a chance to attempt conception), age
cohorts, peri-menopausal women and post-menopausal women.
Inclusion of the whole population or even the entire eligible population
is likely to underestimate prevalence, as does a focus on younger
cohorts of women who have not yet reached the end of their child-
bearing years. Restricting the sample to a post-menopausal population
can result in a biased sample as women with major medical problems
who have a lower survival rate may not be included. This would also
be unhelpful if one is interested in the current size of the infertility
problem from a service provision point of view.
In this study we not only considered women who had tried for a
pregnancy for over 12 months, but also women with a shorter/
unknown duration who had sought medical help for infertility. Since
the latter more closely reflects current clinical practice, we used this
expanded definition for much of the analysis. In terms of primary infer-
tility, either definition yielded similar prevalence rates—indicating that
very few women sought medical help before 12 months. A significant
minority of women (n ¼ 68) with unresolved secondary infertility of
unknown duration sought medical advice without success before
they eventually stopped trying for a baby. We chose to include
them in our infertile group on pragmatic grounds, given that they
had not conceived despite the passage of time. This highlights the
problem with the traditional time-driven definitions of infertility in con-
temporary practice which is characterized by higher public awareness
of infertility (Porter and Bhattacharya, 2008) and early access to
medical services (Oakley et al ., 2008).
In terms of the denominator, we have used the cohort of eligible
women of reproductive age (31–50 years) whose fertility had been
tested. Although we have excluded women with voluntary childless-
ness and those yet to test their fertility, given the current trend
towards delaying the first pregnancy (Maheshwari et al ., 2008) wemay have underestimated the full extent of infertility in younger
women. Menopausal women offer the best opportunity to collect
data on lifetime prevalence of infertility, but inclusion of younger
women allows a better estimate of current reproductive patterns as
well as health seeking behaviour. In this study we have attempted to
do both.
Most studies assessing the prevalence of infertility have been cross
sectional. Despite some early clinic-based work, it is generally believed
that they should be population based, as in this study. Along with most
other studies on infertility, we have used self-reported information.
This has been shown to be reliable and valid for fertility-related data
(Joffe, 1989; Baird et al ., 1991; Zielhuis et al ., 1992). We have
chosen to enquire about actively trying for a pregnancy as well aslack of regular contraception use, reflecting women’s actual behaviour
when contemplating conception (Greil and McQuillan, 2004).
Interpretation of the results of this study needs to take into account
the methods used to define the condition. Our results on lifetime infe-
cundity (absence of any pregnancies) which are least susceptible to
reporting or recall bias are consistent with previous reports.
Although subject to a greater degree of uncertainty, our data on
prevalence do not support an increase in infertility, regardless of the
age cohort or the criteria used to define it. The substantial difference
between the prevalence of primary and secondary infertility suggests
that, as many women seek medical advice and treatment well before
24 months, fewer women than in the past are likely to wait as long as
this, and any definition based on this interval is likely to underestimate
the prevalence of infertility. It seems likely that more women are
seeking medical help early. This is possibly due to greater awareness
of fertility issues among women (Porter et al ., 2006) and the effect of
published guidelines (The Royal College of Obstetricians and Gynaecol-
ogists; National Collaborating Centre for Women’s and Children’s
Health, 2004) suggesting early intervention in cases where there is a
known fertility problem or where the woman is older.
In previous studies, the number of women seeking medical help has
been variously reported as: 25%; (Hirsch and Mosher, 1987) 47.1%;
(Schmidt et al ., 1995) 23–32%; (Rachootin and Olsen, 1981) 44.8%
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(Gunnell and Ewings, 1994). In this study, two-thirds of women with
primary and three-quarters with secondary infertility sought medical
help. With 73.6% of women aged 36–40 and 67.1% of women
aged 46–50 in the present study seeking medical help for infertility,
it appears that Templeton et al ., 1991 earlier figures of 76.5% (36–
40 years) and 62.0% (46–50 years) might have been an overestimate
or could reflect societal changes over time.
Compared with previous data from the same geographical area
(Templeton et al ., 1990), the proportion of women (aged 46–50 years)
with infertility of 24 months duration is lower, although the overall preva-
lence of infertility based on a 12 month definition is similar. This apparent
fall in the numberof women withinfertility of 24 months probably reflects
social andmedical changes in thelast twodecades which have encouraged
a more proactive approach to fertility investigations and treatment. Thisis
consistent with current guidelines on infertility in the UK (The Royal
College of Obstetricians and Gynaecologists; National Collaborating
Centre for Women’s and Children’s Health, 2004) which suggest early
investigationsand treatment in older women andin those with known fer-
tility problems, sometimes even earlier than 12 months. These factors
make it difficult to be confident about an actual fall in the prevalence of
infertility. What is less in doubt, is the fact that there is no evidence tosuggest an increase in the prevalence of infertility. This is broadly consist-
ent with recent data from the USA (Stephen and Chandra, 2006) which
suggest a decrease in infertility rates between 1982 and 2002 as well as
other reports from Europe which do not suggest an increase in time to
pregnancy (Joffe, 2000; Jensen et al ., 2005; Scheike et al ., 2008).
Knowledge about the extent of clinically defined infertility in a popu-
lation is essential to health professionals, health policy-makers and
government in terms of planning healthcare services. Within the UK
there is now formal recognition that infertility is a clinical problem
and there is a commitment by the NHS to fund evidence-based treat-
ment. Critical to the implementation of recommendations made by
the National Institute of Health and Clinical Excellence (NICE;
National Collaborating Centre for Women’s and Children’s Health,2004) in Expert Advisory Group in Infertility Services in Scotland
(EAGISS) is an accurate assessment of the prevalence of infertility in
order to cost and plan service delivery. Awareness about risk
factors associated with infertility is also important in terms of health
promotion. Our results confirm existing data in the literature on the
association between obesity, pelvic problems, including Chlamydial
infection and infertility, which can be translated in terms of useful
and potentially effective public health messages.
The results of this study do not support the view that the preva-
lence of infertility has increased, but do suggest that women are
seeking medical help earlier. This work needs to be replicated on a
larger scale in a wider population to confirm the broader applicability
of the results to the general UK population. Our findings also expose
the weaknesses of current definitions of infertility and emphasize the
need for more methodological work in this area.
Conclusions
The overall prevalence of infertility in a randomly sampled population
of women attempting conception between 31 and 50 is 19.3%.
Nearly 4% of women have unresolved infertility at the end of their
reproductive lives and 9% report being voluntarily childless. Infertility
is associated with endometriosis, Chlamydia trachomatis infection and
pelvic surgery as well as obesity, chemotherapy and some long-term
chronic medical conditions. There is no evidence of an increase in
the prevalence of infertility in this population over the past 20 years.
Contributions
S.B. was the Principal Investigator. He designed the study, led the
funding application, wrote the protocol, managed the project, inter-preted the data and results and wrote the first draft of the paper.
M.P. helped to design the study and to write the funding application.
She designed and piloted the questionnaire, managed the initial
phase of the project, supervised data entry and contributed to the
interpretation of results. A.L. helped design and supervised the statisti-
cal analysis, interpreted the data and results and helped to draft the
paper. E.A.R. performed the statistical analysis and helped interpret
the results. A.T. co-conceived the project, designed the original ques-
tionnaire on which the present version is based, and contributed to
study design and interpretation of results. M.H. helped in the initiation
of the project, study design and interpretation of results. J. K.
co-conceived the study and co-wrote the funding application. She
advised on the study and questionnaire design, data analysis, interpret-
ation of data and had a major input into the final draft of the paper. All
authors commented on and contributed to the final version of this
paper.
Acknowledgements
We would like to thank all the women who completed the question-
naire. Professor Pat Doyle, London School of Hygiene & Tropical
Medicine, commented on study design. Ms Debbie Willox provided
secretarial support and formatted the document.
Funding
The Chief Scientist Office, Scotland funded the study. The views
expressed are those of the authors and not the funding body.
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