The Prevalence of Incidental Simple Ovarian
Cysts ³ 3 cm Detected by Transvaginal
Sonography in Early Pregnancy
Phyllis Glanc, MD,1 Nicole Brofman, MD,2 Shia Salem, MD,3 Anat Kornecki, MD,4
Jason Abrams, BSc,5 Dan Farine, MD6
Department of Medical Imaging, Sunnybrook Health Sciences Centre, Women’s College Hospital, Toronto ON
Clinica Imagem Centro Diagnostico, Florianopolis, Brazil
Department of Medical Imaging, Mount Sinai Hospital, Toronto ON
Department of Diagnostic Radiology and Nuclear Medicine, Faculty of Medicine & Dentistry, London Health Sciences Centre (University
Campus), London ON
Schulich School of Medicine and Dentistry, University of Western Ontario, London ON
Department of Obstetrics and Gynecology, Mount Sinai Hospital Toronto ON
Objective: To determine the prevalence of simple ovarian cysts of Objectif : Déterminer la prévalence des kystes ovariens simples
³ 3 cm diameter detected by transvaginal sonography (TVS) in a dont le diamètre ³ 3 cm qui sont décelés par échographie
population of asymptomatic women in early pregnancy. transvaginale (ÉTV) au sein d’une population de femmes
asymptomatiques aux débuts de la grossesse.
Methods: We conducted a retrospective review of 10 830
consecutive women presenting prior to 14 weeks’ gestational age Méthodes : Nous avons mené une analyse rétrospective portant sur
(GA) for early dating TVS. The records of all women with simple e
10 830 femmes consécutives se présentant avant la 14 semaine
cysts ³ 3 cm in diameter were included. The study population was de gestation (SG) pour une ÉTV de datation précoce. Les
divided into five groups by GA: £ 6 weeks; 6.1–8 weeks; 8.1–10 dossiers de toutes les femmes présentant des kystes simples dont
weeks; 10.1–12 weeks; and 12.1–14 weeks. le diamètre ³ 3 cm ont été retenus. La population à l’étude a été
Results: A simple cyst ³ 3 cm in diameter was present in 4.9% of divisée en cinq groupes, en fonction du nombre de SG :
women at £ 6 weeks’ gestation, in 5.1% between 6.1 and 8 weeks, £ 6 semaines; 6,1–8 semaines; 8,1–10 semaines;
in 5.3% between 8.1 and 10 weeks, in 3.2% between 10.1. and 10,1–12 semaines; et 12,1–14 semaines.
12 weeks, and in 1.5% between 12 and 14 weeks. Overall, a
Résultats : Un kyste simple dont le diamètre ³ 3 cm était présent
simple cyst ³ 3 cm was present in 516 women (4.8%). Prior to 10
chez 4,9 % des femmes à £ 6e semaine de gestation; chez 5,1 %,
weeks, 5.1% had simple cysts ³ 3 cm, dropping to 2.7% after 10 e e
entre la 6,1 et la 8 semaine de gestation; chez 5,3 %, entre la
weeks, a statistically significant decrease (P < 0.0001). Between e e e
8,1 et la 10 semaine de gestation; chez 3,2 %, entre la 10,1 et
10.1 weeks and 12 weeks, the prevalence dropped to 3.2%, and e e
la 12 semaine de gestation; et chez 1,5 %, entre la 12 et la
then to 1.5% in the 12.1–14 week group.
14e semaine de gestation. Globalement, un kyste simple ³ 3 cm
Conclusion: This investigation provides reference data on the était présent chez 516 femmes (4,8 %). Avant la 10 semaine de
prevalence of detecting simple ovarian cysts ³ 3 cm by TVS in an gestation, 5,1 % des femmes présentaient des kystes simples
asymptomatic early pregnancy population. A progressive decline ³ 3 cm, pourcentage qui passait à 2,7 % après la 10 e semaine de
in the frequency of detecting simple ovarian cysts ³ 3 cm begins gestation, soit une baisse significative sur le plan statistique
after 10 weeks’ gestational age. (P < 0,0001). Entre la 10,1 et la 12 semaine de gestation, la
prévalence est passée à 3,2 %, puis à 1,5 % dans le groupe
12,1 –14 semaine de gestation.
Conclusion : Cette recherche offre des données de référence quant
à la prévalence de la détection de kystes ovariens simples ³ 3 cm
par ÉTV au sein d’une population asymptomatique aux débuts de
la grossesse. Un déclin progressif de la fréquence de la détection
de kystes ovariens simples ³ 3 cm se manifeste à la suite de la
Key Words: Ovary, cyst, early pregnancy, transvaginal sonography e
10 semaine de gestation.
Competing Interests: None declared.
J Obstet Gynaecol Can 2007;29(5):502–506
Received on October 16, 2006
Accepted on January 9, 2007
502 l JUNE JOGC JUIN 2007
The Prevalence of Incidental Simple Ovarian Cysts ³ 3 cm Detected by Transvaginal Sonography in Early Pregnancy
Figure 1. Percentage with simple ovarian cysts ³ 3 cm by gestational age
<6 6.1 - 8 8.1 - 10 10.1 - 12 12.1 - 14
Gestational Age (weeks)
INTRODUCTION biometric data (crown–rump length or gestational sac mean
diameter) corresponding to £ 14 weeks’ GA. If a woman
he widespread use of early pregnancy ultrasound exam-
T inations has created controversy about how the addi-
had more than one ultrasound evaluation within the same
pregnancy, only the first was included. Acutely symptom-
tional information should be incorporated into existing
atic women, women with a suspected or confirmed ectopic
management protocols.1 The assessment of the ovaries and pregnancy, and women with higher order pregnancies were
adnexa is considered to be an integral component of the excluded from the study. All ultrasound examinations were
early pregnancy ultrasound examination.2–4 The majority of performed with a 4 to 8 MHz transvaginal transducer
first trimester ultrasound examinations will identify a simple (Phillips ATL 1500) by experienced certified sonographers,
cyst prior to eight weeks’ gestational age (GA).5–7 Typically as was routine in this dating population. All cases were
these represent hormonally responsive cysts in the 1 to 3 cm supervised by a radiologist. The study was approved by the
range, such as the corpus luteal cyst of pregnancy, which Research Ethics Board of Sunnybrook and Women’s Col-
present no risk to the pregnancy. The corpus luteum is lege Health Sciences Centre.
required initially to maintain the pregnancy, with regression
occurring at approximately eight weeks’ gestation as the pla- Standard transvaginal technique was used, with an empty
maternal urinary bladder. Once the transducer was placed
centa takes over progesterone production.5,7–11
into the vagina and advanced to the posterior fornix, an
This study was undertaken to determine the prevalence of a attempt to visualize the ovaries was initially made along
subset of ovarian lesions, the simple cyst measuring ³ 3 cm both sides of the uterus, especially at the level of the cornua.
in diameter discovered incidentally by transvaginal If this method failed, the area along the internal iliac vessels
sonography (TVS) during early pregnancy. This informa- would be insonated. If insonation was unsuccessful, gentle
tion on the prevalence during early pregnancy of the larger manual pressure was applied to the anterior lower abdomi-
simple cyst may be helpful to guide early management of nal wall to bring the ovary to the field of view of the trans-
asymptomatic patients. ducer or to displace overlying bowel loops.
The presence of an ovary was confirmed in two orthogonal
MATERIALS AND METHODS
views, as was the presence of a simple cyst, and the views
The records of a population of women in early pregnancy were recorded on videotape. The maximum diameter of a
presenting consecutively for a dating ultrasound between simple cyst was recorded. A simple cyst was defined as a
January 2000 and December 2003 at the Women’s Health thin-walled anechoic structure with no internal echogenicity
Centre in Toronto, Ontario, were reviewed. The study pop- or septations. Only simple cysts of ³ 3 cm diameter were
ulation included all women with a confirmed intrauterine included in the study. All other ovarian lesions were
pregnancy (yolk sac, embryo, and/or fetus present) and excluded.
JUNE JOGC JUIN 2007 l 503
Size of simple cysts
Gestational age Mean diameter (cm) Maximum diameter (cm)
£ 6 weeks 4.3 10.7
6.1–8 weeks 4.1 12.7
8.1–10 weeks 4.2 8.6
10.1–12 weeks 3.7 5.8
12.1–14 weeks 4.6 5.9
The study population was divided into five chronological difference in prevalence between the first three chronologi-
groups according to gestational ages: £ 6 weeks (group 1); cal GA groups. Between 10.1 and 12 weeks’ GA the preva-
6.1 to 8 weeks (group 2); 8.1 to 10 weeks (group 3); 10.1 to lence reduced to 3.2%, subsequently reducing to 1.5% in
12 weeks (group 4); and 12.1 to 14 weeks (group 5). The the 12.1 to 14 weeks’ GA group.
gestational age groups were compared for the presence of During the four years of the study, the annual overall fre-
ovarian cysts using a chi-square test.
quency of detecting a simple ovarian cyst ³ 3 cm did not
RESULTS vary significantly (ranging from an annual minimum of
4.2% to an annual maximum of 5.5%), suggesting that nei-
The study population included 10 830 pregnant women in ther equipment nor sonographer bias affected the results.
whom both ovaries were visualized. There were 1942 The size range for ovarian cysts across the chronological
women (17.9%) in group 1; 4581 (42.3%) in group 2; 2727 GA groups also did not vary significantly.
(25.2%) in group 3; 1165 (10.8%) in group 4; and 415
(3.8%) in group 5. The scan and reporting protocols DISCUSSION
included routine imaging of the adnexa and comments on
all simple cysts ³ 3 cm in diameter or any complex lesion, The widespread use of diagnostic ultrasound during preg-
thus achieving uniformity in the reporting standard. Lesions nancy has contributed to an increase in the incidental detec-
were characterized as either simple or complex. tion of ovarian lesions. The purpose of our study was to
determine the prevalence of detecting larger simple ovarian
There was an equal distribution of simple cysts in the right cysts of ³ 3 cm diameter by TVS in early pregnancy, thus
ovary and in the left ovary. Overall 272 women (2.5%) had a providing reference data that may be used in counselling
simple cyst ³ 3 cm in the right ovary, 249 (2.3%) had a sim- patients or managing early pregnancies.
ple cyst ³ 3 cm on the left, and 6 (0.1%) had bilateral simple
cysts ³ 3 cm. A complex ovarian lesion was present in 258 The study population comprised consecutive asymptomatic
women (2.4%), and 22 women (0.2%) had both a simple patients who presented for a dating ultrasound in an out-
cyst ³ 3 cm and a complex ovarian lesion. No further analy- patient clinic setting at £ 14 weeks’ GA and who subse-
ses of the complex ovarian lesions were performed for the quently underwent routine TVS. Acutely symptomatic
purposes of this study. patients, patients with a suspected or confirmed ectopic
pregnancy, and patients with higher order pregnancies were
A simple cyst ³ 3 cm was present in 96 women (4.9%) in excluded from the study. The threshold diameter of 3 cm
group 1; in 233 (5.1%) in group 2; in 144 (5.3%) in group 3; was chosen because the routine scan and reporting proto-
in 37 (3.2%) in group 4; and in 6 (1.5%) in group 5 (Figure 1). The cols required specific comments on any simple cyst ³ 3 cm
mean diameter of a simple cyst ³ 3 cm was 4.3 cm (maxi- in diameter or any complex lesion (including hemorrhagic
mum 10.7 cm) in group 1; 4.1 cm (maximum 12.7 cm) in corpus luteal cysts). This diameter (3 cm) of cyst is com-
group 2; 4.2 cm (maximum 8.6 cm) in group 3; 3.7 cm (max- monly used as a threshold to prompt a recommendation for
imum 5.8 cm) in group 4; and 4.6 cm (maximum 5.9 cm) in a follow-up ultrasound.5 Although the reporting structure
group 5 (Table). included quantification and description of the complex
Overall, a simple cyst ³ 3 cm was present in 516 (4.8%) lesions, no follow-up was obtained in these cases, limiting
pregnant women. Prior to 10 weeks’ GA, 5.1% of women the utility of this information.
had simple cysts ³ 3 cm. After 10 weeks’ GA, 2.7% of This study has a number of significant limitations, particu-
women had simple cysts ³ 3 cm, a statistically significant larly the retrospective nature of the data and the lack of lon-
decrease (P < 0.0001) (Figure 2). There was no significant gitudinal data. The strength of the data lies in the large
504 l JUNE JOGC JUIN 2007
The Prevalence of Incidental Simple Ovarian Cysts ³ 3 cm Detected by Transvaginal Sonography in Early Pregnancy
Figure 2. Percentage of simple cysts = 3 cm < or > 10 weeks Gestational Age
< 10 > 10
Gestational Age (weeks) P < 0.0001
number of data points (> 10 000), permitting cross- CONCLUSION
sectional population data analysis on the prevalence of the This study provides reference data on the prevalence of
subset of simple cysts ³ 3 cm during early pregnancy. detecting simple ovarian cysts ³ 3 cm in diameter by TVS in
a population of asymptomatic women with an early preg-
In 99.5% of women with sonographically confirmed preg- nancy. The results demonstrate a progressive decline in the
nancies £ 14 weeks’ GA, one or both ovaries can be visual- frequency of detecting simple ovarian cysts ³ 3 cm after
ized by TVS.12–15 In the present study, a simple cyst ³ 3 cm 10 weeks’ gestational age.
was present in 4.8% of women. Previous reports have sug-
gested a peak incidence of pregnancy-associated ovarian ACKNOWLEDGEMENTS
cystic lesions at approximately eight weeks’ gestation, with
The authors wish to thank Terri Myhr MSc, Research Man-
subsequent regression,6,9 but our findings suggest that
ager at the Research Facilitation Office of the Centre for
regression in the subset of simple cysts ³ 3 cm may be Research in Women’s Health, for undertaking the statistical
delayed until after 10 weeks’ gestation. It is widely acknowl- analysis on the project.
edged that the majority of ovarian masses identified in early
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