Pelvic masses during pregnancy have historically posed diagnostic and therapeutic dilemmas for the obstetrician. Maternal mortality rates with surgery were prohibitive through the early 20th century. For example, among 720 pregnant women with surgically treated adnexal masses reviewed by McKerron (1906), the maternal mortality rate was 21 percent, and the fetal mortality rate was 50 percent.
These high mortality rates with surgical treatment led to further decades during which expectant management was selected. However, conservative care was also associated with excessive mortality rates. Patton (1906) reported a 26-percent maternal death rate with expectant care. Another early study of adnexal masses in pregnancy summarized the many complications with conservative management. These included torsion (33 percent), cyst rupture (5 percent), suppuration (14 percent), and significant dystocia leading to cesarean delivery (16 percent) (Spencer, 1920). Caverly (1931) reported a 30-percent spontaneous abortion rate in cases expectantly managed.
From these experiences, treatment evolved to that of expectant observation until the second trimester, after which time, any mass that persisted was excised surgically. This regimen gained popular acceptance not only because of the high maternal complication rate if the mass remained, but also because of the 2- to 8-percent risk of ovarian malignancy. Following the introduction of modern anesthetic techniques, antibiotics, and blood banking, maternal and fetal morbidity and mortality rates declined. Yet, despite these improvements, management of adnexal masses during pregnancy is still challenging.
The reported incidence of adnexal masses that are discovered during pregnancy varies considerably. Prior to the introduction of sonography, Grimes and colleagues (1954) reported an incidence of 1.2 percent of pregnancies from their private practice. As expected, with the advent of sonographic examination of nearly all pregnancies, the reported incidence is appreciably higher and ranges from 5 to 25 percent in the first trimester (Condous, 2004; Yazbek, 2007). In the second trimester, in a study of more than 24,000 women, an incidence of 4.9 percent was reported (Goh, 2013). The proportion of adnexal masses in pregnancy that are malignant is also variably reported and ranges from 2 to 8 percent. Most of these are tumors of low malignant potential (Leiserowitz, 2006; Ngu, 2014).
The differential diagnosis of an adnexal mass in pregnancy depends on the stage of pregnancy at the time of diagnosis and the sonographic appearance of the mass (Table 14-1). Many women during a routine, first-trimester sonographic examination will have an incidental finding of a small, cystic adnexal mass measuring less than 3 cm. These typically represent functional corpus luteum cysts. In approximately 5 percent of scans, such simple sonographic masses will measure 3 cm or greater (Glanc, 2007; Yazbek, 2007). Most of these larger cysts are also functional, and only 0.7 to 1.7 percent persist beyond the first trimester (Condous, 2004; Yazbek, 2007). Simple cysts that persist into the second trimester are less likely ...