With the routine use of ultrasound incorporated into obstetric care, the frequency at which adnexal masses are diagnosed during pregnancy ranges from 0.5% to 2.2%. Most adnexal masses are asymptomatic, but the potential for ovarian torsion exists whenever an adnexal mass is detected. Adnexal masses are best assessed via pelvic examination and ultrasound in the first trimester. After the first trimester, identification of the adnexa by either clinical examination or ultrasound examination becomes more difficult as the uterus increases in size. When an adnexal mass is noted during pregnancy, specific information with regard to size, location, presence or absence of pain with palpation, mobility, and ultrasound characteristics such as echogenicity, septations, and nodules should be recorded. Approximately 1% of adnexal masses diagnosed during pregnancy prove to be malignant. Ultrasound characteristics that are used to distinguish benign adnexal masses from malignant masses are: size < 5 cm, unilocular appearance, anechoic appearance, and absence of septa or nodules. The differential diagnosis of pelvic masses during pregnancy is quite extensive, including but not limited to the following: leiomyoma, primary ovarian neoplasm, metastatic ovarian neoplasm, hydrosalpinx, ectopic pregnancy, and infection or abscess.

The management of the adnexal mass during pregnancy is conservative if the mass is small (< 5 cm diameter), and has a benign appearance on ultrasound. If the mass is between 5 and 10 cm and appears benign on ultrasound, serial ultrasound every 2–3 weeks is reasonable. If the mass persists or appears malignant, surgical removal is the treatment of choice. If an adnexal mass is greater than 10 cm regardless of ultrasound appearance, surgery is recommended. Because of the increased risk of spontaneous abortion in the first trimester and the increased risk of preterm labor reported in abdominal surgery after 20 weeks, the optimal time for surgery is between 14 and 20 weeks of gestation. It is important that the patient be counseled regarding the following potential complications that may occur during expectant management of adnexal masses during pregnancy: torsion, rupture, hemorrhage, and delayed diagnosis of a malignancy.

Adnexal torsion has been reported to occur in between 7% and 28% of all pregnancies complicated by adnexal masses. When the pregnant patient presents with an adnexal mass and an acute abdomen regardless of gestational age, surgery is indicated. Ovarian torsion should be diagnosed and treated promptly to avoid the development of ovarian necrosis and peritonitis. Torsion most commonly presents with lower abdominal pain that is usually sudden in onset and colicky in nature. The pain may radiate to the flank, back or groin. Nausea and vomiting are commonly associated with the pain, but are nonspecific findings. Only rarely will patients have evidence of abdominal guarding or rebound tenderness at the time of physical examination.

When adnexal torsion is suspected an abdominal/pelvic ultrasound is indicated to evaluate for the presence of an adnexal mass. It is rare for a mass less than 5 cm in diameter to undergo torsion. Usually ultrasound will identify a mass larger than 5 cm unless this occurs in the late second or early third trimester when the size of the uterus can obstruct visualization of the adnexae. The addition of Doppler flow studies may help to differentiate a benign ovarian cyst from one that is undergoing torsion. However, if there is a strong clinical suspicion for adnexal torsion, surgery is warranted. In the first trimester, laparoscopy can be used as a diagnostic and therapeutic procedure. In the second or third trimester, laparotomy is the surgical procedure of choice. At the time of surgery, a cystectomy can usually be performed safely. However, if the ovary appears necrotic, an oophorectomy is required.