A uterine infection has two very different origins. If it starts within ten days of childbirth, a miscarriage, a termination or the fitting of an IUD, it is usually not an STI. If it starts weeks after unprotected sex, chlamydia or gonorrhoea often sits behind it.
The medical name is endometritis.
Here is what I see go wrong most often: those two stories get thrown together. They call for a completely different first step, and the moment your symptoms started is the most useful thing you have.
That is where this article begins.
What is endometritis?
It is inflammation of the lining on the inside of your uterus. Doctors call that endometritis. Bacteria travel up through the cervix, or get in at a moment when the cervix sits wider open than usual. There they can cause redness, swelling and pain.
The cervix normally works as a threshold.
Its mucus holds back most of what lives in your vagina. After childbirth or a procedure, that threshold is temporarily open. Chlamydia and gonorrhoea get past it without any such help (Darville, 2021).
The acute form gives clear symptoms within days to weeks. The chronic form smoulders and is often only found during investigation of repeated miscarriage. The evidence then sits in plasma cells in the endometrium (Michels, 1995).
How do you recognise a uterine infection?
Usually by pain low in your abdomen that does not pass, often together with fever. Alongside it can come discharge that smells or looks different from what you are used to. Bleeding outside your period happens too. Not everyone gets every symptom, and some women barely notice anything.
Fever is the signal to take it seriously.
After childbirth that counts double. Fever in the first ten days after delivery should be assessed the same day by a doctor or midwife. That is not a testing question and not a waiting question.
Without fever it looks like plenty of other things: a bladder infection, ordinary period pain, endometriosis. No single symptom proves it.
What does give you something to hold onto is change. Pain that is new and lasts more than a few days is something a GP can work with. When discharge does and does not point to an STI is covered in discharge and when it points to an STI.
Is it caused by an STI or by something else?
That depends mostly on what happened shortly before your symptoms. If childbirth, a miscarriage, a termination or an IUD came first, that is usually the explanation and it is not an STI. If there was no procedure and there was unprotected sex, chlamydia or gonorrhoea comes into view.
I think it matters to say that out loud, even though we sell STI tests. An infection right after childbirth is usually not an STI question, and a test won't move you forward there.
The difference sits mainly in the timing.
An infection after childbirth or a procedure typically starts within days. An STI that has moved upward can appear weeks to months after the contact, because chlamydia can sit quietly in the cervix first.
This table puts the two stories side by side.
| What happened, and when your symptoms started | Which origin fits | Sensible first step |
|---|---|---|
| Within ten days of childbirth or a caesarean | Fits an infection after delivery, usually not an STI | Midwife or GP the same day, not a self-test |
| Within a week of a miscarriage or a termination | Fits an infection after the procedure | Call the clinic or GP who carried it out |
| In the first weeks after an IUD was fitted | More often fits the fitting than an STI | GP, or the doctor who fitted the IUD |
| Two to six weeks after unprotected sex, no procedure | Fits an STI that has moved upward | Targeted chlamydia and gonorrhoea test, and discuss symptoms |
| Fever, chills or feeling genuinely unwell, whatever the trigger | This is no longer a testing question | See a doctor the same day, do not wait for a result |
| Mild symptoms for months with no clear starting point | Can fit the chronic form, the causes vary widely | GP, an STI test can run alongside |
A table does not make a diagnosis. What it does is stop you waiting on a result when what you actually need is a doctor.
How chlamydia behaves in women is covered in chlamydia in women. What testing around a pregnancy means is covered in STI testing during pregnancy.
Why does it rarely stay in the uterus alone?
Because the fallopian tubes connect directly to it. Inflammation in the uterine lining can run on into the tubes and the tissue around them. That is why doctors use pelvic inflammatory disease as the umbrella term rather than endometritis. In practice several organs are often involved at once.
That is more than a question of words.
The long-term consequences do not come from the uterus itself. They come from the tubes, where scar tissue can narrow the passage.
In Sweden, 1,844 women with laparoscopically confirmed pelvic inflammatory disease were followed for years, alongside 657 women whose laparoscopy showed nothing. Among those trying to conceive, 16.0 percent of patients did not manage it, against 2.7 percent of controls. Ectopic pregnancies occurred in 9.1 percent against 1.4 percent (Weström, 1992).
Read those figures carefully. They describe women in whom inflammation was actually confirmed, not everyone with abdominal pain. What happens in the tubes themselves is covered in salpingitis.
How is it diagnosed?
Through a combination of your history, a physical examination and targeted testing. There is no simple test that confirms or rules out a pelvic infection, and the literature calls that the core problem itself (Hillier, 2021). An ultrasound can look normal while inflammation is genuinely present.
What an STI test does do is find the cause.
A chlamydia and gonorrhoea test says nothing about how far up the bacterium has travelled. It does say whether the cause found most often behind this picture is present. That is exactly what your GP needs.
The NHG-Standaard Het soa-consult describes how Dutch GPs look at these complaints, and Thuisarts.nl explains in plain language what to expect from such a visit. RIVM annual figures have shown for years that chlamydia is the most frequently found STI here.
You can get checked with us through a test for chlamydia, gonorrhoea and trichomonas, without an appointment and without anything reaching your GP records.
How is endometritis treated?
With antibiotics prescribed by a doctor, often a combination, because more than one bacterium is usually involved. With severe symptoms or high fever that sometimes happens in hospital through a drip. Which course fits depends on the origin, which is why that question from the table is not a detail.
Two things get forgotten a lot here.
If an STI sits behind it, your partner should be treated as well. Otherwise you are reinfected the moment you have sex again. And finishing the course counts even if the pain has gone after three days.
What you do not do is reach for an old course of antibiotics in the cupboard.
Picture this: you are 29, you had an IUD fitted six weeks ago, and since yesterday you have pain low down with some fever. Six weeks is late for a fitting problem. Calling your GP makes more sense than waiting it out.
What if you have no symptoms?
Something can still be going on. Chlamydia runs without noticeable symptoms in a large share of women, and it is exactly those silent infections that get the time to move upward. The chronic form of endometritis is sometimes only found once someone has been trying to conceive for months.
That is the strongest argument I know for testing after a risk moment.
Not because something is wrong, but because a test is the only way to find a silent infection. How symptom-free STIs behave is covered in STIs without symptoms.
One concrete first step costs you five minutes. Write down exactly when your symptoms started and what happened in the four weeks before, and take that note to your GP.
Further reading
For the umbrella picture of the ascending infection: pelvic inflammatory disease. For what can happen to your fertility afterwards: blocked fallopian tubes.
References
- Michels TC. Chronic endometritis. American Family Physician, 1995. PMID 7604765.
- Darville T. Pelvic Inflammatory Disease Due to Neisseria gonorrhoeae and Chlamydia trachomatis: Immune Evasion Mechanisms and Pathogenic Disease Pathways. The Journal of Infectious Diseases, 2021. PMID 34396413.
- Hillier SL, et al. A Review of the Challenges and Complexities in the Diagnosis, Etiology, Epidemiology, and Pathogenesis of Pelvic Inflammatory Disease. The Journal of Infectious Diseases, 2021. PMID 34396398.
- Weström L, et al. Pelvic inflammatory disease and fertility. A cohort study of 1,844 women with laparoscopically verified disease and 657 control women with normal laparoscopic results. Sexually Transmitted Diseases, 1992;19(4):185-92. PMID 1411832.
- RIVM, Sexually transmitted infections in the Netherlands, annual report. Accessed July 2026.
- NHG-Standaard Het soa-consult, Dutch College of General Practitioners. Accessed July 2026.
- Thuisarts.nl, I have pain in my lower abdomen. Accessed July 2026.
Every test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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