Ovarian Cysts in Pregnancy

Found on a scan you had for another reason

Ovarian cysts in pregnancy are almost always incidental findings — spotted at an early dating scan, or at a scan arranged for pain or bleeding. The NHS describes ovarian cysts as very common and notes that "in most cases, cysts do not cause symptoms. Many are found during a routine pelvic exam or imaging test done for another reason."

ACOG describes the commonest type: "Functional cyst — This is the most common type of ovarian cyst. It usually causes no symptoms. Functional cysts often go away without treatment within 6 to 8 weeks." Other types it names include teratomas, cystadenomas and endometriomas, and it notes that most ovarian cysts "are benign (not cancer) and go away on their own without treatment".

Early pregnancy has its own particular cyst. The corpus luteum, the structure left behind after ovulation, persists to produce progesterone until the placenta takes over, and it often looks like a cyst on an early scan. Corpus luteum cysts typically resolve during the second trimester without any intervention.

The gap in UK guidance, stated plainly

The main UK guideline in this area is RCOG Green-top Guideline No. 62 on suspected ovarian masses in premenopausal women, and its own summary says what it does not cover: "the guideline does not specifically address the acute presentation of ovarian cysts or the management of ovarian cysts in pregnant women".

That sentence is why advice about cysts in pregnancy varies more between hospitals than you might expect. There is no national UK protocol specific to pregnancy, so units apply general principles — watchful waiting where a cyst looks simple and small, imaging follow-up, and specialist referral where features are concerning. We are not going to invent a protocol that does not exist.

Torsion, and the pain that should not wait

The complication that matters most is ovarian torsion, where the ovary and its blood supply twist. It is more likely in pregnancy than outside it, partly because of ovarian enlargement and partly because of the changing position of the uterus, and the risk is concentrated in the first trimester and around the time of the second-trimester uterine growth spurt.

The NHS advice for cyst-related emergencies is direct: seek an urgent GP appointment or help from NHS 111 if "you have sudden, severe pelvic pain". Torsion typically causes sudden, severe, one-sided pain, often with nausea and vomiting, sometimes coming in waves as the ovary twists and untwists.

This is not pain to sleep on. An ovary that stays twisted loses its blood supply, and the difference between an ovary that can be saved and one that cannot is measured in hours. Go to your maternity unit or emergency department rather than waiting for a routine appointment.

Rupture is the other acute complication, again causing sudden pain, sometimes with internal bleeding. Both present the same way to you, and both need the same response: urgent assessment.

When surgery is considered

Most cysts in pregnancy are watched rather than removed. Surgery is considered where there is torsion or rupture, where a cyst is large enough to threaten obstruction later in pregnancy, or where imaging features raise concern about malignancy.

Where planned surgery is needed, the second trimester is generally preferred, because the risks associated with the first trimester have passed and the uterus is not yet large enough to make access difficult. Emergency surgery, by contrast, happens whenever it is needed.

Ovarian cancer in pregnancy is rare, but a cyst with concerning ultrasound features is investigated rather than assumed benign. Note that the blood marker CA125, used outside pregnancy as part of assessing an ovarian mass, is unreliable in pregnancy because pregnancy itself raises it — so a raised result is interpreted very differently, and RCOG's guideline on ovarian masses does not extend its algorithms to pregnant women.

What follow-up usually looks like

For a simple-looking cyst with no concerning features, follow-up is usually a repeat scan after an interval to see whether it has resolved or changed. Many will have gone by the time of the anomaly scan.

Ask three things: whether the cyst has features that make it simple or complex on ultrasound, its size in centimetres, and when the repeat scan is booked. Those three answers tell you most of what there is to know, and they should all be in your notes.

What it means for the rest of your pregnancy

An ovarian cyst that resolves has no ongoing implications, and NICE guideline NG201 antenatal care continues unchanged. A persistent cyst is followed and, in most cases, still causes nothing.

The NHS notes that "ovarian cysts do not usually prevent you getting pregnant, although they can sometimes make it harder to conceive", and that where surgery is needed "your surgeon will aim to preserve your fertility whenever possible". That applies to future pregnancies as much as this one.

If your cyst is being watched, be clear with yourself about the pain that would send you in: sudden, severe, one-sided, not settling. Everything else can go through your normal antenatal contacts.

Cysts found during fertility treatment or very early pregnancy

If you conceived through IVF or with ovulation induction, early scans often show enlarged ovaries with multiple cysts. That is a consequence of the stimulation rather than a new problem, and it usually settles over the first trimester.

The situation to be alert to in that group is ovarian hyperstimulation syndrome, which causes abdominal swelling, breathlessness, reduced urine output and rapid weight gain, and which needs assessment by the fertility unit rather than by a general service. Say that you have had fertility treatment whenever you are assessed.

Where the evidence gap leaves you

Because RCOG Green-top Guideline No. 62 states that it "does not specifically address... the management of ovarian cysts in pregnant women", decisions are made by individual teams applying general principles. That has one practical consequence for you: ask for the reasoning, not just the plan.

If watchful waiting is proposed, ask what would change the plan and when the next scan is. If surgery is proposed, ask what the concern is, why now rather than after birth, and what the alternative would be. These are reasonable questions in an area where no national protocol exists to point at.