1. Ø The strongest two sources we used are the pooled analysis and the
prospective cohort studies. The weakest source is case control.
Ø All the articles demonstrated a positive correlation between
nulliparity and risk of ovarian cancer.
Ø Some of the limitations of most of the studies are that they did not
control for potential confounding variables such as socioeconomic
status and age.
Ø A few articles had potential risks for selection biases such as
Berkson's bias and recall bias. Some women were admitted to the
hospital for other medical conditions, which can increase the risk
for ovarian cancer.
Ø A possible reason for the positive association between nulliparity
and ovarian cancer has been attributed to the changes that a woman
undergoes during pregnancy. During this time, her ovaries do not
release additional eggs, and there are changes in the levels of
different hormones in her body. These changes are thought to help
protect women against ovarian cancer.
Ø Additionally, according to the pooled analysis article, another
reason for this positive association is the “incessant ovulation”
hypothesis, which postulates that every ovulation provokes micro-
traumas to the ovaries and exposure to follicular fluid. This is
suggested to increase the risk of ovarian cancer.
Nulliparity
and
Ovarian
Cancer
Nour
Matar
-­‐
Zaynab
Albahrani
–
Jady
Lubin
–
Sophia
El
moumni
Epidemiology,
Faculty
of
Health
Sciences
of
the
University
of
OUawa
Discussion
Results
Introduction
Methods
Abstract
References
Pooled
analysis
Reproductive
factors and risk
of ovarian cancer
Factors and Risk of
Epithelial Ovarian
Cancer
Risk factors for ovarian
cancer
Hormonal risk factors for
ovarian cancer
Infertility, fertility drugs, and
invasive ovarian cancer
Risk Factors for Invasive Epithelial
Ovarian Cancer
Reproductive and hormonal factors and
ovarian cancer
Figure 1: Hierarchy of research design of the articles used from strongest to
weakest
Figure 2. Reprinted by: Riman, T., Dickman, P., Nilsson, S., Correia, N., & al, e. (2001). Risk Factors for
Invasive Epithelial Ovarian Cancer: Results from a Swedish Case-Control Study, 367.
Figure 3. Reprinted by: Mosgaard, B., Lidegaard, O., Kjaer, S.K., & al, e. (1997). Infertility,
fertility drugs, and invasive ovarian cancer: a case-control study, 1008.
Ø Ovarian cancer is an abnormal growth of cells in one or both of the
ovaries that can spread to different parts of the body. Epithelial ovarian
cancer is the most common, in which the spread of the cancer begins from
the epithelial tissue covering the ovaries.
Ø The main symptoms of epithelial ovarian cancer are abdominal pain,
eating disorders and urinary problems (Webmed, 2013).
Ø According to the American Cancer Society, approximately 21 290 women
are newly diagnosed with ovarian cancer in America and about 14 180
women die because of it each year (American Cancer society, 2015).
“Is there an association between nulliparity and the risk of developing
ovarian cancer for women in North America and Europe?”
Ø This study aimed to assess a relationship between ovarian cancer and and
nulliparity ( i.e. does nulliparity increase the risk of developing ovarian
cancer), through a structured literature review.
Search Strategy
“Nulliparity AND risk of
ovarian cancer”
Included Search Words:
“United States of
America”, “Canada”,
“Europe”.
Excluded any non-English
articles
Database used:
Medline Ovid (n=233)
After Reading Abstracts,
Excluded:
(n=1) Obesity
(n=2) Specific Ethnicity
(n=2) Infertility
(n=4) Different cancers
Studies Used (n=8)
Prospective Cohort Studies (n=2)
Case-Control Studies (n=5)
Pooled Analysis (n=1)
Potential Articles for
Structured Literature
Review (n=17)
Conclusion
Ø There was a positive correlation between nulliparity and
ovarian cancer.
Ø For future directions, more research should be done to
reduce the amount of regular ovulations for women who
decide not to have children in order to decrease the micro-
traumas to the ovaries. However, it is important that this
treatment does not result in any negative impacts on a
woman’s health.
Ø Furthermore, as stated in one of the aforementioned
articles, further studies are needed to examine whether the
various histological types of tumors have different
etiologies (Hankinson, 1995).
Association between nulliparity and the risk of ovarian cancer : A Structured
Literature Review
Nour Matar1, Zaynab Albahrani2, Jady Lubin3, Sophia El moumni4
1Fourth year Health Sciences student at the University of Ottawa. 2 Fourth year
Health Sciences student at the University of Ottawa. 3 Fourth year Health Sciences
student at the University of Ottawa. 4 Fourth year Health Sciences student at the
University of Ottawa.
Background: Ovarian cancer is the fifth most common type of cancer, especially
in white women. About 50% of the diagnosis are among age 63 years and older
(American Cancer Society, 2015). Previous studies have shown an association
between reproductive factors such as nulliparity and postmenopausal ovarian
cancer (Hankinson, 2012).
Objective: To determine if an association exists between nulliparity and the
development of ovarian cancer for women in North America and Europe.
Method: Conducting a structured literature review through databases such as
Medline (Ovid).
Results: Obtained 17 different studies, chose 8 of which 2 were prospective
cohort, 5 were Case-Control, 1 was a pooled analysis (meta-analysis). Obtained
RRs , ORs, and CIs depending on the study.
Conclusion: A positive correlation between nulliparity and the development of
ovarian cancer was found.
Figure 4. Reprinted by: Chiaffarino, F., Pelucchi, C., Parazzini, F., & al, e. (2001). Reproductive and
hormonal factors and ovarian cancer, 339
Meta-­‐Analysis
Prospec/ve
Cohort
Case-­‐Controls
Name of Study Type of
study
Sample population Quantitative Measurements Results
1. Hormonal risk factors
for ovarian cancer in the
Albanian case-control
study
Case-
control
study
Cases
N = 283
Age: 24-74
Controls
N = 1019
-Frequency and distribution
analysis
-Chi square test of Pearson
-P-values (significant if <0.05)
-Odds Ratios OR (12.5)
-95% CI
- Strong association between
nulliparous women and ovarian
cancer risk.
- Decreased risk with increasing
number of childbirths.
2. Pooled analysis of 3
European case-control
studies: I. Reproductive
factors and risk of
epithelial ovarian cancer.
Meta-
analysis of
3 cases-
controls
studies
(Italy, UK
and Greece)
1st Study (Italy)
Cases
N = 755
Age: <75
Women with ovarian cancer
Controls
N = 2033
2nd Study (UK)
Cases
N = 235
Age: <65
Women with ovarian cancer
Controls
N = 451
3rd Study (Greece)
Cases
N = 150
Women with malignant ovarian
cancer
Controls
N = 250
-Relative Risk
0 children RR (1)
1 child RR (0.7)
3 children RR (0.5)
4 children RR (0.3)
-95 % CI
- Nulliparity and delay of first birth
until the age of 35 increases the risk.
- Having more children is a
protective factor for ovarian cancer.
3. Ovarian epithelial
tumors and reproductive
factors
Case-
control
study
Cases
N = 1031
Age: median of 56
Women with histologically confirmed ovarian
cancer
Controls
N = 2411
Age: median of 57
Women with the same geographical areas and
admitted to the same hospitals as cases, with acute
conditions unrelated to risk factors for ovarian cancer.
-Odds ratio
3 births OR (0.6)
> 4 births: OR (0.4)
-95% CI
Multiparity was associated with a
significant reduction in risk of
ovarian cancer.
4. Infertility, fertility
drugs, and invasive
ovarian cancer: a case-
control study
Case-
control
study
Cases
N = 684
Age: 18-59
Exclusion criteria:
Non-Danish inhabitants, those who had
malignancies other than ovarian cancer.
Controls
N = 1721
Women matched for area of residence and day/month
of birth.
Exclusion criteria: women who had undergone
bilateral oophorectomy
-Odds ratios
1 birth OR (0.47 to 1.02)
≥ 2 birth OR (0.33 to 0.69)
-95% CI
-Nulliparous women had an
increased risk of ovarian cancer
compared with parous women
-Nulliparity implies a 1.5 to 2 fold
increased risk of ovarian cancer.
5. Risk factors for
invasive Epithelial
Ovarian Cancer: Results
from a Swedish Case-
Control Study
Case-
control
study
Cases
N = 655 cases
Age: 50-74
Exclusion criteria: Women without any
previous ovarian malignancies or bilateral
oophorectomy.
Controls
N = 4148
Randomly selected women from a continuously
updated population register
Exclusion criteria: women who reported previous
bilateral oophorectomy.
-Parity reduced epithelial
ovarian cancer risk
-Odds ratio OR (0.61) for
uniparous compared with
nulliparous women.
-95% CI
-Parity reduced risk for uniparous
compared with nulliparous women
6. Reproductive factors
and risk of ovarian
cancer: a prospective
study
Prospective
cohort study
N = 63,090
Age: 27-69
Exclusion criteria: surgical removal of one or both ovaries, or other operations on the ovaries or
hysterectomy.
-Odds ratios >5 births OR (0.4)
-95% CI
-The risk of ovarian cancer declined
with increasing parity.
7. A Prospective Study of
Reproductive Factors and
Risk of Epithelial Ovarian
Cancer
Prospective
cohort study
N = 121,700
Age: 30-55
Female registered nurses
Exclusion criteria: participants who were diagnosed with cancer or who removed one or both ovaries.
-Relative Risk (RR) between
parity and ovarian cancer = 0.84
-95% CI
-A statistically significant inverse
association was observed between
parity and ovarian cancer risk.
8. Risk Factors for
Ovarian Cancer: a case
control-study
Case
Control
Study
Cases
N = 235
Diagnosed with epithelial ovarian cancer
Controls
N = 451
-Relative risk (RR) between
parity and ovarian cancer = 1.7
-95 % CI
-Nulliparous women had
a higher risk of ovarian cancer than
parous women
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