Urine infection is common in pregnancy. If left untreated, some urine infections may progress to cause serious kidney infection. Treatment is with a medicine called an antibiotic. The aim is to cure the infection and also to prevent possible complications.
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.
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).
- Blood in your urine.
- Symptoms of cystitis as above.
- Feeling generally unwell.
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.
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).
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.
What is the treatment for a urine infection in pregnancy?
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).
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 and references
Antenatal care for uncomplicated pregnancies; NICE Clinical Guideline (March 2008, updated February 2019)
Management of suspected bacterial urinary tract infection in adults; Scottish Intercollegiate Guidelines Network - SIGN (updated July 2012)
Guidelines on Urological Infections; European Association of Urology (2015)
Urinary tract infection (lower) - women; NICE CKS, July 2015 (UK access only)
Chickenpox in Pregnancy; Royal College of Obstetricians and Gynaecologists (January 2015)
Zika virus; Public Health England
Rash in pregnancy; Public Health England
Diabetes in pregnancy: management of diabetes and its complications from preconception to the postnatal period; NICE Clinical Guideline (February 2015 - last updated August 2015)
Hypertension in pregnancy; NICE Clinical Guideline (August 2010, updated 2011)
Obstetric Cholestasis; Royal College of Obstetricians and Gynaecologists (May 2011)
Gurung V, Middleton P, Milan SJ, et al; Interventions for treating cholestasis in pregnancy. Cochrane Database Syst Rev. 2013 Jun 246:CD000493. doi: 10.1002/14651858.CD000493.pub2.