If you are female of reproductive age, then it is completely normal for your ovaries to produce cysts. ALL women produce ovarian cysts. In fact, you can’t get pregnant without one! Every month, your ovary produces a few small cysts which each grow out of a follicle containing an egg on the surface of the ovary. The fluid within the cyst helps to awaken and ripen the egg to prepare it for potential fertilization. The ‘winner’ cyst is the biggest of the follicles and will grow up to 1 ½ inches (or 3 cm.) in size. In the middle of your cycle (approximately 14 days after the first day of your last period), your body sends out a surge of hormones which prompts the ‘winner’ or dominant cyst to burst open and release the egg. The egg then travels into the fallopian tube where it begins its journey to the uterus. If the egg is fertilized, which usually happens while it is still in the tube, it will continue on its way and implant into the uterus and start to grow. If it isn’t fertilized, then it will be shed with the lining of uterus when you get your period.
Sometimes, there can be two (or more) cysts which mature and grow big enough to rupture and each produce a ripe egg. This is how fraternal (non-identical) twins, triplets, or more (yikes!) are conceived.
Meanwhile, if the egg is fertilized, the cyst on your ovary often remains, growing a thick yellow coating and is known as a corpus luteum. This cyst is a good thing with an important function: it secretes progesterone which helps to plump the lining of the uterus and optimize the implantation and growth of the early pregnancy. The cyst may disappear within a few weeks of conception or a few months. They will eventually go away by themselves, usually no later than 20 weeks.
How can you tell the difference between a normal cyst and an abnormal cyst?
Functional (normal) ovarian cysts and corpus luteums (normal cysts after conception) have a typically simple appearance and look like a solid black circle on ultrasound. Your doctor can also tell a corpus luteum by its distinct ring of blood flow which can be seen with color Doppler ultrasound. If he/she sees either of these types of cysts, they will be unconcerned and no follow up is needed. However, cysts that might be abnormal do not appear clean but will have muck, solid portions, and/or septations within them that are easily visible on ultrasound. Most of the time, this is due to a hemorrhage or bleed within the cyst which, like a bruise, your body will reabsorb and clean up on its own. Some blood or debris is quite common in a corpus luteum and is nothing to worry about, but a later ultrasound will likely be needed to confirm that it did go away as expected. Any cyst, no matter how clean or simple it may appear, will also be monitored with follow up ultrasounds if it is bigger than 2 inches (5 cm.). Most of the time, these DO go away on their own by the end of the first trimester, even the larger or painful ones.
Do these cysts cause pain?
Most of the time, a corpus luteal cyst causes no pain and you are unaware it is even there. Occasionally, there can be some pain if the cyst bleeds into itself or ruptures. Neither of these events are serious or will threaten the pregnancy but they can be associated with some mild or even severe pain on your lower right or left side. You should always call your doctor or midwife if you have severe pain or you are concerned, but rest assured that it is very unusual that these cysts require any type of intervention or surgery. The pain should subside and gradually go away within a few days or a week. If the pain is severe and associated with fever, you will want call your doctor or midwife right away to rule out appendicitis or other potential causes for your pain.