Ovarian Vein Thrombosis: A Rare Clot After Childbirth or Surgery

Ovarian vein thrombosis (OVT) is a blood clot in one of the two veins that carry blood away from the ovaries. It is rare, and it mostly happens in the days after childbirth, especially after a caesarean, or after pelvic surgery or infection. It usually causes fever and pain low in the tummy or side, which can easily be mistaken for appendicitis or a kidney infection. It is treatable, but it needs prompt medical care.

Get help now: if you have recently given birth or had pelvic surgery and develop fever with tummy or side pain, see a doctor the same day. Call 995 in Singapore for chest pain, sudden breathlessness, coughing up blood, or feeling faint.

What is ovarian vein thrombosis?

Each ovary has a vein that runs up the back of the abdomen. The right ovarian vein drains straight into the inferior vena cava, the body’s main vein. The left one drains into the left kidney (renal) vein. Our guide to how the pelvic veins are laid out explains this in more detail.

In OVT, a clot forms inside one of these veins and partly or fully blocks it. Doctors also call it gonadal vein thrombosis, because the ovarian veins are the female gonadal veins. It is a type of venous thromboembolism, the same family of problems as a deep vein thrombosis (DVT) in the leg.

Who gets it, and why?

Three things make blood more likely to clot: slow blood flow, damage or inflammation in a vein wall, and blood that clots more easily than usual. Around the time of childbirth, all three are present. That is why most cases are linked to pregnancy.

Known triggers include:

• The weeks after giving birth. Cases peak a few days after delivery and are more common after a caesarean than a vaginal birth. They can also follow a miscarriage or termination.
• Pelvic surgery, such as hysterectomy or other gynaecological operations.
• Pelvic infection, including infection of the womb lining after delivery.
• Cancer, especially in the abdomen or pelvis, and its treatment.
• Hormonal medicines containing oestrogen, such as some contraceptive pills.
• Inflammatory bowel disease or an inherited tendency to clot.

In a minority of women, no clear trigger is found.

How rare is it? Estimates vary widely between studies, but symptomatic OVT is thought to affect only a small fraction of a percent of births. It is more often found by chance on scans done for other reasons, particularly in people having cancer care.

Symptoms: what does a blood clot in an ovary vein feel like?

The classic picture is a woman a few days after giving birth who has:

• Fever that does not settle, sometimes despite antibiotics
• Pain in the lower tummy, side (flank) or back, often on one side
• Nausea, vomiting or a general sense of being unwell
• A tender, rope-like lump that a doctor can sometimes feel in the abdomen

About three-quarters of cases are on the right side. The reasons are not fully understood. One explanation often given is that the enlarged womb tends to turn slightly to the right in late pregnancy, pressing on the right ovarian vein and slowing the flow in it.

Left ovarian vein thrombosis causes the same kinds of symptoms, but on the left. Because the left vein drains into the left kidney vein, a clot there can sometimes extend towards the kidney.

These symptoms overlap with appendicitis, kidney infection, infection of the womb, an ovarian cyst or twisted ovary, and other causes of fever after birth. That overlap is why OVT is often found only when a scan is done.

Is ovarian vein thrombosis serious?

It can be, and it should be treated as a medical problem that needs attention. The main risks are:

• The clot spreading into the inferior vena cava or the left kidney vein
• Pulmonary embolism, when part of the clot breaks off and travels to the lungs. This is uncommon but can be life-threatening
• Sepsis, a serious body-wide reaction to infection, when OVT comes with a pelvic infection

With modern treatment, deaths from OVT are now rare, and most women recover fully. Prompt diagnosis is the key.

How is it diagnosed?

Your doctor will ask about recent birth, surgery, infection and medicines, examine your tummy, and usually arrange blood tests to look for infection. Imaging confirms the clot:

• Ultrasound with Doppler is safe and quick and is often done first. The ovarian veins can be hard to see, especially with gas in the bowel, so a normal ultrasound does not always rule OVT out.
• CT scan with contrast is widely used and shows the clot and how far it extends.
• MRI avoids radiation and is very accurate, but it is slower and less widely available.

Read more about CT and MRI scans of the pelvic veins. Sometimes OVT is found by chance on a scan done for a different reason, with no symptoms at all.

Ovarian vein thrombosis treatment

Treatment depends on how unwell you are, what caused the clot and how far it reaches. The main approaches are:

• Anticoagulants (blood thinners). These stop the clot growing and let the body break it down over time. Injections, tablets, or one followed by the other may be used. Courses of around three to six months are commonly suggested after a pregnancy-related clot, but the evidence behind any exact length is limited, and your doctor will tailor it to you. Some medicines are safe while breastfeeding and some are not, so mention it if you are.
• Antibiotics, usually through a drip at first, if infection is suspected.
• Follow-up scans may be arranged to check the clot has settled.

Surgery to remove the clot or tie off the vein is now rarely needed. A filter in the main vein is only considered in unusual situations. Clots found by chance, without symptoms, are not always treated; this is a decision for your specialist.

We do not give medicine doses here. Always follow the plan from your own doctor, and ask what to do if you have bleeding, bruising or a planned procedure while on blood thinners. A Singapore vascular surgeon’s guide to deep vein thrombosis explains blood-thinner treatment for clots more generally.

How is it related to pelvic congestion syndrome?

They involve the same veins but are different problems:

• In ovarian vein thrombosis, the vein is blocked by a clot, usually suddenly, with fever and pain.
• In pelvic congestion syndrome, the vein is wide open, with faulty valves letting blood fall backwards. The pain is a long-lasting, dull ache that builds through the day.

A blocked ovarian vein can push blood into side branches, and some specialists think this may add to pelvic vein congestion later, but good evidence is lacking. Separately, a small clot in a pelvic vein is one of the possible complications of ovarian vein embolisation, the procedure used to treat PCS. If you are worried about clots and pelvic veins more generally, see whether pelvic congestion syndrome is serious.

Will it happen again?

Repeat clots after a pregnancy-related OVT appear to be uncommon in published studies. If you are planning another pregnancy or thinking about hormonal contraception, tell your doctor about the clot. They may suggest avoiding oestrogen-containing medicines or using preventive blood thinners around a future birth.

When to see a doctor

See a doctor the same day if, in the weeks after childbirth, a miscarriage or pelvic surgery, you develop:

• Fever, chills or feeling generally unwell
• New or worsening pain in the lower tummy, side or back
• Pain with nausea or vomiting

If you are already on treatment for OVT, contact your doctor about any unusual bleeding, black stools, blood in your urine, or a new severe headache.

Call 995 in Singapore for an emergency, including:

• Sudden shortness of breath or chest pain, especially when breathing in
• Coughing up blood
• A fast heartbeat, fainting or feeling very faint
• Severe tummy pain with high fever, confusion or cold, clammy skin
• One leg suddenly swollen, painful and warm

If you are not sure which specialist to see for a vein problem, our page on finding a specialist may help.

This article is general information, not personal medical advice. Please speak to a doctor about your own symptoms. How we create our content.