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Urine Infection in Pregnancy

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Urine infection is common in pregnancy. If it is not treated some infections may progress to cause a serious kidney infection. Treatment is with a medicine called an antibiotic. The aim is to cure the infection, and also to prevent possible complications.

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

A urine infection is caused by germs (bacteria) that get into your urine. This may cause:

  • Asymptomatic bacteriuria. This is where bacteria are found in your urine, but are not causing any symptoms.
  • Bladder infection (cystitis). This is common in both 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. Symptoms may include pain in your loin (the side of the abdomen over your kidney), fever, feeling sick (nausea), being sick (vomiting) and/or diarrhoea, and blood in your urine. You may also have symptoms of cystitis. Not all the symptoms may develop. Sometimes a kidney infection can just cause vague symptoms such as feeling generally unwell.

Most urine infections are caused by germs (bacteria) that 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 and into your bladder. Some bacteria thrive in urine and multiply quickly to cause infection.

Women are more prone to urine infections than men, as their urethra (the tube from the bladder that passes out urine) is shorter and opens nearer the anus. Pregnant women are also more prone to urine infections than non-pregnant women. This is partly due to the hormonal changes of pregnancy that affect the urinary tract and tend to slow down the flow of urine.

If you have a kidney infection when you are pregnant, you can feel very unwell. But 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).

  • 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 should also have your urine tested if you develop symptoms of bladder infection (cystitis) or kidney infection at any stage during pregnancy.

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 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).

But, when you do not have symptoms, it may help to have plenty to drink to flush out the bladder frequently. It is thought that this may help to prevent urine infections.

Original Author:
Dr Tim Kenny
Current Version:
Peer Reviewer:
Dr Tim Kenny
Document ID:
4613 (v40)
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The Information Standard - certified member
See also: Lower Urinary Tract Symptoms in Women written for professionals
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