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Obstetrics & Gynecology 1999;93:585-589
© 1999 by The American College of Obstetricians and Gynecologists
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ORIGINAL RESEARCH

Predictors of Persistence of Adnexal Masses in Pregnancy

LISA M. BERNHARD, MD, PEGGY K. KLEBBA, MD, DIANA L. GRAY, MD and DAVID G. MUTCH, MD

From the Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri.

Address reprint requests to: Lisa M. Bernhard, MD, Department of Obstetrics and Gynecology, Washington University School of Medicine, 216 South Kingshighway, Suite 5300, St. Louis, MO 63110, E-mail: bernhardlm{at}msnotes.wustl.edu


   Abstract
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Abstract
Materials and Methods
 Results
 Discussion
 References
 
Objective: To determine factors predicting the persistence of sonographically identified adnexal masses in pregnancy.

Methods: All patients from March 1988 to April 1993 diagnosed with an adnexal mass by obstetric sonography were reviewed. Examinations had been entered prospectively into our sonography database. Follow-up data were collected from the database, from hospital and pathology department records, and from interviews with referring obstetricians. Adnexal masses were characterized by size, sonographic appearance, and anatomic site. Persistence of the masses was determined by subsequent sonography, operative findings, or postpartum physical examinations.

Results: The rate of adnexal masses during pregnancy was 2.3% (432 of 18,391). Complete follow-up was available for 422 of 432. Most of the adnexal masses (76%; 320 of 422) were simple cysts with a mean diameter less than 5 cm. The remainder of the masses were simple or complex, measuring 5 cm or more in diameter. Seventy of 102 large or complex masses resolved. By multivariate analysis, the best predictors for persistence of these masses were complex appearance on sonography and size of the mass (P < .05 for both categories).

Conclusion: Most adnexal masses identified by sonography during pregnancy were small, simple cysts that did not pose a risk to the pregnancy. Even the majority of large or sonographically complex masses resolved. The best predictors of persistence of the masses were sonographic appearance and size.

Traditionally, adnexal masses in pregnancy have been treated by surgical extirpation, with its associated risks, costs, and potential morbidity and mortality.1–4 The rationale for this therapy was based on the 10–30%1–4 rate of pregnancy complications in these women. The rate of torsion has been quoted as 7–28%,2,3,5,6 and the incidence of malignancy at 2–8%.1,7–9 Most large series that have evaluated adnexal masses in pregnancy were published before the widespread use of obstetric sonography. Therefore, the diagnosis of an adnexal mass in a pregnant woman often depended on palpable masses or symptoms such as pain. In this setting, an adnexal mass is more likely to be of clinical significance.

Over the last 15–20 years, the use of obstetric sonography has increased dramatically, so that 60–70%10 of obstetric patients in the United States now have at least one sonographic examination during pregnancy. One consequence of the increased use of prenatal ultrasound has been increased detection of incidental adnexal masses, especially in the first and early second trimesters. Recent studies in which prenatal sonographic examinations were commonly used suggested that the finding of an adnexal mass in pregnancy may no longer carry the same prognosis as it did during the preultra-sound era.11–15 Our aims in this study were to determine the rate of adnexal masses in an obstetric population who had sonographic examinations and to identify factors that predict the persistence of adnexal masses.


   Materials and Methods
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Abstract
 Materials and Methods
Results
 Discussion
 References
 
We reviewed all obstetric ultrasound examinations in which an adnexal mass or cyst was identified from March 1988 to April 1993 by the Washington University Medical Center Ultrasound/Genetics Division. Results of the obstetric ultrasound examinations were accessed from a computerized database. Adnexal masses had been coded numerically and entered into the database at the time of the sonographic examination. Inspection of the adnexa was a routine part of obstetric sonographic examinations. Sonographic examinations were done with a variety of machines, including ATL Ultra-mark 4, 8, and 9 (Advanced Technology Laboratories, Bothell, WA), Acuson 128XP (Acuson, Mountain View, CA), and GE 3000 (General Electric Corp., Norcross, GA). Examinations were done by registered diagnostic medical sonographers and were reviewed and interpreted by sonologists experienced in obstetric and gynecologic scanning.

Clinical information on pregnancy outcomes was obtained from the computerized database and hospital chart reviews and was confirmed by telephone interviews with the referring obstetricians. The length of follow-up for cases in the database was at least 6 weeks postpartum. Historic data included maternal age, gravidity, parity, medical history, and obstetric history (including the use of ovulation induction agents). Clinical data included gestational age at diagnosis of the adnexal mass, indications for ultrasound examination, sonographic findings, gestational age at delivery, mode of delivery, birth weight, presence of fetal growth restriction, indication for delivery, indication for adnexal surgery, gestational age at removal of the adnexal mass, pregnancy complications including those attributable to the mass, operative findings, and histopathologic findings, when available.

Adnexal masses were classified sonographically by size, number of cysts (unilocular or multilocular), echotexture (cystic, solid, or cystic-solid), laterality (unilateral or bilateral), and anatomic site if known (ovarian, tubal, uterine, or nongynecologic). Masses were categorized sonographically into four groups: simple cysts less than 5 cm in mean diameter, simple cysts 5 cm or more in mean diameter, multicystic masses (masses containing more than one simple cyst), or complex masses. Simple cysts were defined as cysts that were smooth-walled and devoid of internal echoes. Complex masses were defined as either solid masses or masses not meeting the criteria for simple cysts. All simple cysts with mean diameters greater than 1 cm, all multicystic masses, and all complex masses regardless of size were included for analysis. To determine the persistence or resolution of adnexal masses, we reviewed the follow-up ultrasound examinations, operative findings, or postpartum physical examinations. The decision regarding the necessity for surgical intervention or cesarean delivery was made by the individual managing physician.

Univariate statistical analysis was done using the two-tailed Student t-test with Bonferroni correction for variables measured on an interval scale, and the z test and {chi}2 analysis for variables measured on a nominal scale. Stepwise logistic regression analysis was done to evaluate the influence of mass size, sonographic appearance, use of ovulation induction agents, and presence of symptoms on the persistence of the adnexal mass. P < .05 was considered significant.


   Results
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Abstract
 Materials and Methods
 Results
Discussion
 References
 
During the study period, 18,391 obstetric ultrasound examinations were performed. Four hundred thirty-two women with adnexal masses were identified, giving a rate of adnexal masses of 2.3% among women having obstetric ultrasound examinations in our institution. Complete follow-up was available for 422 of the 432 patients with adnexal masses in pregnancy. Three hundred twenty (76%) of the masses were simple cysts with a mean diameter of less than 5 cm. The remaining 102 masses (24%) were complex masses, multicystic masses, or simple cysts with a mean diameter of at least 5 cm (Figure 1Go). No adverse outcomes were associated with the simple cysts that measured less than 5 cm. Specifically, none of the women in this group required surgical intervention for their cysts, experienced torsion of the mass, or had an adnexal malignancy.



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  		Figure 1. Categorization of the sonographic appearance of adnexal masses in pregnancy.

 
The remainder of the analysis focused on the 102 women with large, multicystic, or complex adnexal masses. Masses resolved in 70 of these women; 25 had surgical removal of the mass, and the mass persisted but was not removed surgically in the remaining patients. In two of these patients with a persistent mass, the mass was most consistent in appearance with a myoma. In one subject, small bilateral, complex ovarian masses were believed to be most consistent in sonographic appearance with endometriosis and remained unchanged in size and appearance on serial sonography for several years. In the fourth subject, a long-standing endometrioma was found at the time of cesarean delivery but was not removed. The final subject in this group had two small complex cysts and had conceived while taking clomiphene citrate. The cysts were detected at 8.5 weeks of pregnancy and persisted at the patient’s next examination at 11.5 weeks. At this time fetal death was noted, and no further follow-up was available. Seven patients (7%) had cesarean delivery specifically because of the masses. One woman had torsion of the mass. This patient had an 8.3-cm, sonographically complex, palpable mass with pain, and had not used ovulation induction agents. The one patient with a tumor of low malignant potential was an asymptomatic 35-year-old woman with a 9.2 cm sonographically complex mass detected on a dating scan at 10 weeks’ gestation. No invasive ovarian carcinomas were found.

When the masses were categorized by sonographic appearance, 18 were simple cysts with mean diameters of 5 cm or more, 39 were multicystic masses, and 45 were complex masses. Our analysis showed that women with simple cysts measuring 5 cm or more or with multicystic masses were less likely to undergo surgical intervention than women with complex masses (11%, 0%, and 56%, respectively; P < .05). No significant differences were noted among the groups in the incidence of cesarean or torsion.

On clinical presentation, 80 patients were asymptomatic and had no physical findings suggestive of an adnexal mass, and 22 patients had the masses detected by palpation or subjective symptoms of pain. Compared with women in whom the masses were incidental findings, women who presented with palpable masses or pain were more likely to have surgical removal of the masses (45% versus 21%; P = .046) and were more likely to undergo cesarean (14% versus 1.25%; P = .037). No statistically significant difference was noted in the rates of torsion (4.5% versus 0%) between women with and those without symptoms.

Twenty-nine of 102 women (28%) were treated with ovulation induction agents before conception. Although there were no surgical interventions in the ovulation induction group, 27 of 73 patients in the group without ovulation induction underwent surgery (P < .001).

Women who did not have surgery (75 of 102) were evaluated as a separate group for complications related to the mass and for spontaneous resolution of the mass. In the expectantly managed group, 19% were symptomatic, 39% had conceived with ovulation induction agents, and 27% had a sonographically complex mass. Within this group, outcomes were good, with 92% (69 of 75) of the masses resolved (95% confidence interval 86%, 98%). There were no cases of torsion or malignancy in this group.

Univariate analysis showed that the following factors were associated with persistence of the mass: clinical presentation, sonographic appearance of the mass, and antecedent use of ovulation induction agents. Women who presented with clinical symptoms were less likely to have masses that resolved (45% versus 74%; P = .02) than were asymptomatic women. Women with simple cysts of 5 cm or more and those with multicystic masses were more likely to have their masses resolve than were patients with complex masses (83% and 95% versus 40%, respectively; P < .05). Twenty-seven of 29 masses resolved in the ovulation induction group versus 43 of 79 (59%) in the group without ovulation induction (P = .002). Complex sonographic appearance remained a significant predictor of persistence on multiple logistic regression analysis (P < .003). Size of the mass was also a significant predictor of persistence by multivariate, although not by univariate, analysis (P < .001). The use of ovulation induction agents and clinical presentation were not significant predictors of persistence by multivariate analysis (P = .058 and P = .53, respectively).

Histopathologic examination was done on 29 of 31 masses removed (four cases of bilateral masses). The results showed 12 benign cystic teratomas (39%), eight cystadenomas (26%), four endometriomas (13%), one chronic ectopic, one hemorrhagic corpus luteum, one tumor of low malignant potential, one struma ovarii, and one cavernous hemangioma of the liver (3%). Final histopathology was not known in two cases.


   Discussion
Top
Abstract
 Materials and Methods
 Results
 Discussion
References
 
As expected, we found the rate of adnexal masses in pregnancy to be higher in a population undergoing obstetric sonography than in a population who presented with pain or a palpable adnexal mass. We found a rate of adnexal masses in pregnancy of 2.3% (432 of 18,391), compared with a rate of one in 81 to one in 25001–3,7,8 reported in studies in which the masses were detected by clinical evaluation alone. This finding was not unexpected because ultrasound examination is able to detect masses smaller than those usually detected by physical examination, especially during pregnancy. Our subjects included many who were asymptomatic and in whom the adnexal mass was an incidental finding. When women with simple cysts less than 5 cm were excluded, the detection rate in our study decreased to one in 180. This figure is similar to that found by Hogston et al.11 In their study, the prevalence of adnexal cysts in a group of women having obstetric sonography was one in 190.

The rates of torsion of the mass (1%) and malignancy (1%) in the subgroup of women with large or complex masses in our study are lower than those reported in the preultrasound era but are comparable to more recent studies.3 Bromley and Benacerraf12 reported a rate of malignancy of one in 131 among adnexal masses of 4 cm or greater that persisted beyond 12 weeks’ gestation. Hogston et al11 reported a one in 137 incidence of malignancy among sonographically detected ovarian masses during pregnancy. In that series, the incidence of torsion of the mass was one in 120.11

Our findings confirm those of others who evaluated the importance of sonographically detected adnexal masses during pregnancy and have important implications for management.11–15 Many incidental adnexal masses will be detected by sonography in the first or second trimester of pregnancy.15 Most of these masses will be small, simple cysts (mean diameter of less than 5 cm) that will resolve spontaneously and present no risk to the pregnancy.14,15 Our data suggest that these cysts should be managed expectantly unless clinical symptoms dictate otherwise. Even among women with large simple cysts, multicystic masses, and complex masses, many masses will resolve spontaneously and thus can be managed safely without surgery. Surgery is more appropriate when the masses are persistent. Previous investigators have confirmed that persistent masses are more likely to be malignant or neoplastic and are therefore more appropriately managed surgically.16–20 In our series, the one case of ovarian malignancy (tumor of low malignant potential) was a 9.3-cm mass with a complex sonographic appearance. The one case of torsion also occurred in a woman with a sonographically complex mass (hemorrhagic corpus luteum cyst).

Our standard practice is to assign a probable cause of adnexal masses based on sonographic appearance and clinical presentation. Masses are described as functional or physiologic, suggestive of endometriosis, consistent with benign neoplasia (including ovarian teratoma when the appearance is typical), or suggestive of malignancy. Bromley and Benacerraf,12 among others, have found a high degree of accuracy in predicting the tissue diagnosis of an adnexal mass based on sonographic appearance. They were able to identify correctly 95% of dermoid tumors, 80% of endometriomas, and 71% of simple cysts. The one case of ovarian malignancy in their series was a complex mass with features suggestive of malignancy. Although difficult to demonstrate objectively in our study, we agree that the sonologist’s subjective assessment of the cause of the mass is important in managing these patients. Of the 27 masses removed surgically, 25 were complex. Only one of the masses removed was functional, and that case involved torsion of an ovary containing a hemorrhagic corpus luteum cyst.

Our study has several limitations. The true prevalence of adnexal masses in pregnancy cannot be determined by sonography alone. True prevalence can be determined only by surgical examination of all adnexa. Because this was an observational study involving many independent managing physicians, the management of the adnexal masses was neither preset nor uniform. Therefore, the natural history of some of these masses could not be determined. The rate of persistence or resolution of all adnexal masses could not be determined with complete accuracy because some masses destined to resolve might have been removed. A related limitation is the method of ascertainment of persistence of the masses. Some of the masses were followed with serial sonography or were confirmed at surgery; however, assessment of persistence of many of the masses (especially the small simple cysts) was done by postpartum physical examination. We have already noted the difficulty in identifying small adnexal masses by physical examination and realize that some of the small masses noted by sonography may have been persistent despite a normal physical examination. Additionally, it is possible that some complications related to the masses might not have occurred until after the 6-week postpartum examination, so they would not have been identified by our study. Another limitation of our study is that although we suspect that the sonologist’s assessment of the cause of the mass played an important role in subsequent management, we were unable to document this objectively. A possible limitation in the sonographic assessment of the masses is that color flow and pulsed Doppler were not consistently used or reported. In our experience, however, color flow and pulsed Doppler findings rarely change the impression made from gray-scale sonographic findings. Therefore, we believe it is unlikely that the uniform addition of color flow and pulsed-wave Doppler technology to the sonographic assessment of the masses would have changed the sonologist’s diagnosis. Another potential confounder is the relatively high proportion of women who had used ovulation induction agents (29 of 102; 28%) in the group with large, multicystic, or complex masses. Because this subgroup of women uniformly did well, they may have skewed the results of the whole group toward a more favorable outcome. Finally, although multiple logistic regression analysis found that the size of the mass was an important predictor of persistence (higher likelihood of persistence with increasing size of the mass), we could not determine a finite cutoff value for the size at which a mass will persist. Therefore, no clear recommendation can be made for removal of masses based on size.

We believe our data, and those of other investigators,13 provide enough information on the prognosis of adnexal masses in pregnancy to justify a randomized clinical trial of surgical versus nonsurgical management of large or sonographically complex adnexal masses in pregnancy.


   Footnotes
 
PII S0029-7844(98)00490-6

Received May 22, 1998. Received in revised form October 2, 1998. Accepted October 22, 1998.


   References
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Abstract
 Materials and Methods
 Results
 Discussion
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