Pregnancy is frequently a women’s first contact with the health care system and often her first pelvic ultrasound examination. This first sonogram can reveal previously unknown adnexal pathology. Approximately 4% of pregnant women will have an adnexal mass detected by sonography and 1% to 2% of these masses will persist. It is estimated that up to 7% of these persistent masses will be malignant. Sonography plays an important role in differentiating benign from malignant adnexal masses and physiological from pathologic masses and should be used judiciously to complement evaluation and help guide treatment.