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Clinical Reviews

A guide to management: Adnexal masses in pregnancy

Forego surgery in most cases until delivery—or until the risky first trimester has passed

March 2007 · Vol. 19, No. 03


CASE 1 An enlarging cystic tumor

A 20-year-old gravida 3 para 1011 visits the emergency department with persistent right flank pain. Although ultrasonography (US) shows a 21-week gestation, the patient has had no prenatal care. Imaging also reveals a right-sided ovarian tumor, 14×11×8 cm, that is mainly cystic with some internal echogenicity.

At 30 weeks’ gestation, a gynecologic oncologist is consulted. Repeat US reveals the mass to be about 20 cm in diameter and cystic, without internal papillation. The patient’s CA-125 level is 12 U/mL. Based on this information, the physicians decide the likely finding is a benign ovarian cystadenoma.

How should they proceed?

The discovery of an adnexal mass during pregnancy isn’t as rare as you might think—depending on when and how closely you look, it occurs in about 1 in 100 gestations. In most cases, we have found, the mass is clearly benign (TABLE 1), warranting only observation.


Adnexal masses removed during pregnancy: Histologic profile




549 (33)


451 (27)


204 (12)


237 (14)


55 (3)

Benign stromal

28 (2)


23 (1.5)


8 (0.5)


55 (3)


68 (4)



Data supplied by the authors from surgical experience

In the case described above, the physicians followed the patient and removed the mass at term because it was cystic with no other indications of malignancy. At 37 weeks’ gestation, a cesarean section was performed through a midline laparotomy incision, followed by removal of the ovarian tumor, which was benign. The pathologist measured the tumor at 16×12×4 cm and determined that it was a corpus luteum cyst.

Presence of mass raises questions

Despite the rarity of malignancy, the discovery of an ovarian mass during pregnancy prompts several important questions:

How should the mass be assessed? How can the likelihood of malignancy be determined as quickly and efficiently as possible, without jeopardy to the pregnancy?

When is surgical intervention warranted? And when can it be postponed? Specifically, is elective operative intervention for a tumor that is probably benign appropriate during pregnancy?

When is the best time to operate? And what is the optimal surgical route?

In this article, we address these questions with a focus on intervention. As we’ll explain, only a small percentage of gravidas who have an adnexal mass require surgery during pregnancy. When surgery is necessary, it is usually indicated for an emergent problem or suspicion of malignancy. Even when ovarian cancer is confirmed, we have found that it is usually in its early stages and therefore has a favorable prognosis (TABLE 2).


Malignant adnexal masses removed during pregnancy




101 (28)

Borderline epithelial

147 (40)

Germ-cell dysgerminoma

47 (13)


34 (9)


24 (7)


5 (1.4)


2 (0.5)


4 (1.1)



Data supplied by the authors from surgical experience

How should a mass be assessed?

Ultrasonography and other imaging often reveal the presence of a mass and help determine whether it is benign or malignant. In fact, most adnexal masses discovered during pregnancy are incidental findings at the time of routine prenatal US. (see the most commonly found tumors.) Operative intervention is required in 3 situations:

  • malignancy is suspected
  • an acute complication develops
  • the sheer size of the tumor is likely to cause difficulty.

Common adnexal tumors found during pregnancy

Corpus luteum

A persistent corpus luteum is a normal component of pregnancy. Although it usually appears as a small cystic structure on ultrasonographic imaging, the corpus luteum of pregnancy can reach 10 cm in size. Other types of “functional” ovarian cysts may also be found during pregnancy. Most functional cysts resolve by the early second trimester.4,6 In rare cases, a cyst may develop complications such as torsion or rupture, causing acute pain or hemorrhage. Otherwise, a cystic tumor identified in the first trimester should be characterized and followed using ultrasonography (US).

Benign neoplasm

An adnexal mass that persists beyond the first trimester is more likely to be a neoplasm.3-5,10,11,22 Such a mass is generally considered clinically significant if it exceeds 5 cm in diameter and has a complex sonographic appearance. Usually such a neoplasm will be a benign cystadenoma or cystic teratoma.5,10-13,19,23,24

Benign cystic teratoma

This tumor can be identified with a fairly high degree of specificity using a variety of imaging techniques, with management based on the presumptive diagnosis. This tumor is unlikely to grow substantially during pregnancy. When it is smaller than 6 cm, such a tumor can simply be observed.14 A larger tumor can occasionally rupture or lead to torsion or obstruction of labor, but such occurrences are rare.

Benign cystadenoma

In an asymptomatic patient with imaging that suggests a benign cystadenoma (see sonogram), benign cystic teratoma, or other benign tumor, observation is reasonable in most cases.4,6,7,9-11,14,19 Operative intervention is required when there is less certainty regarding the benign nature of the tumor, an acute complication develops, or the tumor is expected to pose problems because of its large size alone.

Uterine leiomyoma

It is rare for an ovarian tumor detected during pregnancy to have a solid appearance on US. When it does, it may be a uterine leiomyoma mimicking an adnexal tumor (see intraoperative photograph). It should be reevaluated with more detailed US or magnetic resonance imaging.25


About 10% of adnexal masses that persist during pregnancy are malignant, according to recent series.4,5,7-10,12,13,24,26

Most of the ovarian cancers diagnosed during pregnancy are epithelial, and a substantial portion of these are low-malignant-potential (LMP) tumors.5,10,11,13,19,23,24,26,27 This ratio is in keeping with the age of these women, which also explains the stage distribution (most are stage 1) and the large percentage of germ-cell tumors detected. The majority of ovarian cancers discovered in pregnant women have a favorable prognosis.

Benign-appearing cystadenoma

A morphologically benign-appearing, large, cystic adnexal mass can be seen in association with an 11-week gestation.

Leiomyoma mimics an ovarian tumor

This 17-week gestation was marked by a large pedunculated leiomyoma that at fist appeared to be a right adnexal tumor.

Appearance of adnexal masses on US

A functional cyst such as a follicular cyst, corpus luteum cyst, or theca lutein cyst usually has smooth borders and a fluid center. Other cysts may sometimes contain debris, such as clotted blood, that suggests endometriosis or a simple cyst with bleeding into it.

A benign cystic teratoma often has multiple tissue lines, evidence of calcification, and layering of fat and fluid contents.

A benign cystadenoma usually has the appearance of a simple cyst without large septates, whereas a cystadenocarcinoma often contains septates, abnormal blood flow, increased vascularity, or all of these. However, it is impossible to definitively distinguish a cystadenoma from a cystadenocarcinoma using US imaging alone.

Functional cysts usually resolve by the second trimester. A cyst warrants closer scrutiny when it persists, is larger than 5 cm in diameter, or has a complex appearance on US.

CA-125 may be useful after the first trimester

The serum CA-125 level is typically elevated during the first trimester, but may be useful during later assessment or for follow-up of a malignancy.1

A markedly elevated serum level of alpha-fetoprotein (fractionated in some cases) has been reported in some gravidas with an endodermal sinus or mixed germ-cell ovarian tumor.2 Alpha-fetoprotein should be measured when there is suspicion for a germ-cell tumor based on clinical or US findings.

When a mass is discovered during cesarean section

Occasionally, an adnexal mass is detected at the time of cesarean section (FIGURE 1).3 This phenomenon is increasingly common, given the large number of cesarean deliveries in the United States. To eliminate the need for future surgery and avoid a delay in the diagnosis of an ovarian malignancy, inspect the adnexa routinely after closing the uterine incision in all women who deliver by cesarean section.

FIGURE 1 Mass discovered at cesarean section

This cystic tumor was discovered at cesarean section that was undertaken for obstetric indications.

CASE 2 LMP tumor is suspected

A 36-year-old gravida 3 para 1011 makes a prenatal visit during the first trimester. Her previous delivery was a cesarean section through a Pfannenstiel incision for a breech presentation. US imaging reveals a 6-week, 5-day fetus and a complex left adnexal mass, 4.5×3.9×4.1 cm. Imaging is repeated 1 month later at a tertiary-care center and shows an 11-week viable fetus, a right ovary with a corpus luteum cyst, and a left ovary with a 6.6×4 cm cystic mass with extensive vascular surface papillations that is suspicious for a low-malignant-potential (LMP) tumor. In several sonograms prior to the pregnancy, this mass appeared to be solid and was 3 cm in size.

When is surgery warranted?

Surgery is indicated when physical examination or imaging of a pregnant woman reveals an adnexal mass that is suspicious for malignancy, but the physician must weigh the benefit of prompt surgery against the risk to the pregnancy. This equation can be complicated in several ways. For example, surgical staging of clinically early ovarian cancer is more difficult due to the pregnant uterus, which is more extensively manipulated during these procedures. In addition, an optimal operation sometimes necessitates removal of the uterus.

At 13 weeks’ gestation, the patient described in case 2 underwent laparoscopy with peritoneal washings and left salpingo-oophorectomy, but the tumor ruptured during removal. Final pathology showed it to be a serous LMP tumor involving the surface of the left ovary. Washings were in line with this diagnosis.

The pregnancy continued uneventfully, and a repeat cesarean section was performed at 37 weeks through the Pfannenstiel scar, followed by limited surgical staging. Exploration and all biopsies were negative, and the final diagnosis was a stage 1C serous LMP tumor of the ovary.

The patient articulated a desire to preserve her fertility and was monitored with US imaging of the remaining ovary every 6 months.

Does ‘indolent’ behavior of malignancy justify watchful waiting?

LMP tumors comprise a relatively large percentage of ovarian “cancers” encountered during pregnancy. Some authors report the accurate identification of these tumors prospectively, based on ultrasonographic characteristics.4,5 When an LMP tumor is the likely diagnosis, serial observation during pregnancy may be appropriate because of the indolent nature of the tumor. Further studies are needed to refine preoperative diagnosis and determine the overall safety of this approach.

When the problem is acute

In rare cases, a pregnant patient will have (or develop during observation) an acute problem due to torsion or rupture of an adnexal mass. Some ovarian cancers may present acutely, such as a rapidly growing malignant germ-cell tumor or a ruptured and hemorrhaging granulosecell tumor. Emergent surgery is necessary to manage the acute adnexal disease and reduce the likelihood of pregnancy loss. These events are infrequent, occurring in less than 10% of women with a known, persistent adnexal mass during pregnancy.4-14 Furthermore, recent studies have not found a substantial pregnancy complication rate associated with such emergency surgeries.

CASE 3 Suspicious mass, ascites signal need for surgery

A 19-year-old gravida 1 para 0 seeks prenatal care at 17 weeks’ gestation, complaining of rapidly enlarging abdominal girth. The physical examination estimates gestational size to be considerably greater than dates, but US is consistent with a 17-week intrauterine pregnancy. Imaging also reveals a 12-cm heterogenous left adnexal mass and a large amount of ascites.

Surgery is clearly warranted, but how extensive should it be?

When a malignancy is detected, a thorough staging procedure may be justified, depending on gestational age, exposure, desires of the patient, and operative findings. A midline incision is preferred.

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