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Urine Infection in Pregnancy

Urine Infection in Pregnancy

A urine infection means having germs (bacteria) somewhere within the urinary tract, ie the bladder, kidneys or the tubes between (the ureters). In pregnancy, a urine infection is more likely to cause complications, and so usually needs treatment.

Most women are, unfortunately, familiar with the typical symptoms of a urine infection. You feel as though you are busting for a pee all the time. But when you go to the loo, only a dribble comes out and it burns or stings when it does. There may be an ache in the lower part of your tummy (abdomen) too. However, urine infections don't always cause symptoms, particularly in pregnancy. Sometimes it is only picked up during one of the routine tests of your urine.

If the infection spreads up your urinary tract towards your kidneys, the symptoms change. You may get back pain and/or a high temperature (fever). There may be blood in your urine.

How did I get it?

Normally, there are no germs (bacteria) in urine. However, if you have a urinary infection, the germs from elsewhere in your body have made their way up the urinary tract. These are usually germs from your guts - after all, the exit points for poo and wee in your body are particularly close together. After doing a poo, some of those germs can end up on the skin between the two, and make their way from there to the urine tube (urethra).

Germs then travel up the urethra, which leads to the bladder, and may spread further up the next set of tubes (ureters) to your kidneys. Because women don't have a penis, the tube between their bladder and the outside world is much shorter than that of a man. This makes women more prone to urine infections.

Side view of female genitals and cross-section diagram of urinary tract

When you are pregnant, you are even more prone to urine infections. This is partly because of changes caused by your pregnancy hormones and partly because your enlarged womb (uterus) is squashing your bladder, so it doesn't empty as effectively as it usually does.

Why is it different in pregnancy?

A urine infection in pregnancy is more likely to cause complications than it is in somebody who is not pregnant. If you have a urine infection, you are more likely to go into labour early, and more likely to have a smaller baby. In pregnancy the germs (bacteria) are more likely to spread towards your kidneys, giving you a more serious infection called pyelonephritis. For these reasons, if germs are found in your wee in pregnancy, you would normally be advised to take a course of antibiotics, even if you have no symptoms at all.

Fortunately, antibiotics are usually very effective at clearing the infection up, thereby preventing any of these problems.

What is a urine infection and what are the symptoms?

A urine infection is caused by germs (bacteria) which get into your urine. Usually the germs have come from your skin, and travelled up the tubes of the urinary system. The symptoms may depend on how far up your system the germs have travelled. The germs may cause:

  • Asymptomatic bacteriuria. In this situation bacteria are found in your urine but are not causing any symptoms. You will only know you have it if your urine is tested.
  • Bladder infection (cystitis). This is common, both in pregnant and non-pregnant women. Typical symptoms are pain when you pass urine and passing urine more often. You may also have other symptoms such as pain in your lower tummy (abdomen), blood in your urine, and a high temperature (fever).
  • Kidney infection (pyelonephritis). This is uncommon but may occur as a complication from cystitis or asymptomatic bacteriuria. It is usually a more serious infection, making you feel very unwell. Some or all of the possible symptoms may occur, which include:
    • Pain in your side (loin) over your kidney.
    • Having a high temperature.
    • Feeling sick (nausea).
    • Being sick (vomiting).
    • Diarrhoea.
    • Blood in your urine.
    • Symptoms of cystitis as above.
    • Feeling generally unwell.

Can a urine infection affect my pregnancy?

If you have a kidney infection when you are pregnant, you can feel very unwell. If left untreated, it may also cause problems such as early labour and/or a small baby. A kidney infection is uncommon but may develop as a complication from a bladder infection (cystitis) or from a urine infection. There may be no symptoms at first (asymptomatic bacteriuria).

Understanding the urinary tract

There are two kidneys, one on each side of the tummy (abdomen). They make urine which drains down tubes called ureters into the bladder. Urine is stored in the bladder. It is passed out through a tube (the urethra) which carries urine from the bladder when we go to the toilet.

Side view of female genitals and cross-section diagram of urinary tract

What causes a urine infection?

Most urine infections are caused by germs (bacteria) which come from your own bowel. They cause no harm in your bowel but can cause infection if they get into other parts of your body. Some bacteria lie around your back passage (anus) after you pass a stool (faeces). These bacteria can sometimes travel to your urethra (the tube from the bladder that passes out urine) and into your bladder. Some bacteria thrive in urine and multiply quickly to cause infection.

Women are more prone than men to urine infections, as their urethra is shorter and opens nearer the anus. Pregnant women are also more prone than non-pregnant women to urine infections. This is partly due to the hormonal changes of pregnancy which affect the urinary tract and tend to slow down the flow of urine. It also may be that the enlarged womb (uterus) presses on the bladder and prevents it draining as well. If urine does not drain quickly from the bladder, germs are more able to multiply and cause an infection.

Less commonly there may be other causes of a urine infection. If you have to have a tube (called a catheter) passed into your bladder, it is easier for germs to directly reach your bladder, and this may make urine infection more likely. Occasionally for people whose immune systems are not working well, the infection may spread through the bloodstream rather than up the urinary tubes.

When is my urine checked during pregnancy?

  • You should usually have your urine tested early in pregnancy. Your midwife may ask you to bring a sample in a container or sample bottle. Treatment is advised if any germs (bacteria) are found - even if you have no symptoms. If bacteria are found, you should have regular routine urine tests throughout the pregnancy.
  • You will normally be asked to bring a urine sample at each of your antenatal checks. How often this is depends on how your pregnancy is progressing and whether you have any problems or complications.
  • You should also have your urine tested if you develop symptoms of bladder infection (cystitis) or kidney infection at any stage during pregnancy.

How is urine tested?

You will normally be asked to provide what is called a midstream urine sample. This means you pee the first part into the toilet, the next bit into the bottle, and the end of the stream back into the toilet. This is so that the part of the urine being tested is just the urine itself, and isn't being muddled with any of the germs it has flushed off your skin.

Your urine can be tested very quickly, in a minute or two, with a dipstick test. This gives an indication as to whether there may be an infection. It also can check for:

  • Sugar. Your urine may contain sugar if you have developed diabetes in pregnancy (gestational diabetes)
  • Protein. Your urine may contain protein if your blood pressure is too high in a condition called pre-eclampsia. Infection can also result in protein in the urine sample.
  • Ketones. Your urine may contain ketones if you are lacking in fluid (dehydrated).
  • Blood. Your urine may contain blood if you have an infection, or if you have some pregnancy-related bleeding.

If the dipstick is completely clear, an infection is unlikely. If it tests positive, the sample will be sent to the lab for further analysis. This test takes a few days but will show which germs are causing your infection. It will also show the best antibiotic to treat it.

What is the treatment for a urine infection when you are pregnant?

Antibiotic medicines

There are several different types of antibiotic that can help. Your doctor will choose the type most likely to help you. A seven-day course of an antibiotic is the usual treatment. Any symptoms will usually improve within a few days. However, it is very important that you complete the course of antibiotics. The choice of antibiotic used may be different when you are pregnant. The antibiotics used to treat urine infections in pregnant women are safe to take in pregnancy. They will not harm your baby.

You should see a doctor if your symptoms do not go, or if you feel worse after a few days. Some germs (bacteria) are resistant to some antibiotics. This can be identified from tests done on the urine sample. A change of antibiotic is needed if the bacterium is found to be resistant to the first antibiotic.

Note: this is a little different to the treatment of bladder infection (cystitis) in non-pregnant women. Not having any treatment is an option in non-pregnant women, as cystitis often goes without treatment. However, if you are pregnant, treatment with an antibiotic is usually advised.

You should do a further sample of urine when you have finished your antibiotics. This will check the infection has been treated properly.


Paracetamol will usually ease any pain, discomfort, or high temperature (fever).

Drinking fluids

If you have cystitis then having plenty to drink is traditional advice to flush out the bladder. However, there is no proof that this is helpful when you have cystitis. Some doctors feel that it does not help, and drinking lots may just cause more (painful) toilet trips. Therefore, it is difficult to give confident advice on whether to drink lots or just to drink normally when you have mild symptoms of cystitis. However, if you have a fever and/or feel unwell, having plenty to drink helps to prevent lack of fluid in the body (dehydration).

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.

Dr Mary Harding
Peer Reviewer:
Dr Laurence Knott
Document ID:
4613 (v42)
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