I am 35 and 13 weeks into my second pregnancy. Four weeks ago, I went to the hospital for pain in my lower right quadrant. A sonogram showed a cyst on my right ovary, about 15cm. The doctor has had me in bed since then, and I have had two more sonograms. It hasn't gone down. The doctors seem to think it is fluid-filled and not cancerous. Can cysts really go down on their own? How long should I wait to see if it will go down? Have you heard of any cysts this large during pregnancy, and do they pose a danger to the baby?

Alberta

Cysts (fluid-filled structures) can go down on their own, but it is unlikely a 15cm cyst in pregnancy will do so. Cysts are not that uncommon during pregnancy, affecting about 1 in 1,000 pregnant women. The vast majority of ovarian masses found during pregnancy are benign; the incidence of ovarian cancer is 1 in 25,000 births. Ultrasound can be helpful in determining if a mass is benign or malignant, but it cannot do so with 100 percent certainty. If ultrasound shows that the mass is strictly fluid-filled, without septation or thick walls, it is probably benign.

The problem with large, even benign, cysts during pregnancy is that they may rupture or torse (twist on themselves). Either of these events leads to significant pain for mom and the potential for miscarriage or preterm labor and delivery for the baby. Large (more than 6-8cm) cysts are usually removed surgically if they do not decrease in size spontaneously over the course of a few weeks. In pregnancy, the best time to operate is in the second trimester, ideally around 14-16 weeks. Occasionally, a cyst may be dealt with via laparoscopy, but very large cysts often require a large, open incision.

A 15 cm cyst is rather big, and the potential for complications like rupture is high. If it has remained for more than two weeks, I suggest you talk to your doctor about your option. Your doctor may have been just watching you for now, until you get out of the first trimester (the first 13 weeks of pregnancy). I have removed several masses this size during pregnancy, and all of my patients went on to deliver normal, healthy babies.