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Causes of Preterm Labor: Testing For Infections



  1. More than 12 percent of infants born in the United States are premature. Forty percent of those births are associated with intrauterine infections.
  2. Common infections that can cause preterm labor in pregnant women are bacterial vaginosis (BV) and urinary tract infections (UTIs).
  3. Treatments for BV and UTIs are relatively simple, but during pregnancy they may lead to complications.

Labor is considered preterm when a woman goes into labor at 37 weeks or earlier. The typical time frame for going into labor is 40 weeks.

Having a baby prematurely can lead to complications. Some newborns may develop physical or intellectual disabilities if infections are not addressed.

Two common infections include bacterial vaginosis (BV) and urinary tract infections (UTIs). At the moment it’s not clear why they can cause preterm labor.

Infections in pregnancy

More than 12 percent of infants born in the United States are premature. Forty percent of those births are associated with intrauterine infections, such as BV or UTIs.

About 10 to 30 percent of pregnant women contract BV during pregnancy. It is the result of an imbalance of bacteria in the vagina. It isn’t a sexually transmitted infection, but it is associated with vaginal sex. You can increase your risk of getting BV by having a new sexual partner, multiple sexual partners, or by douching.

According to the America Pregnancy Association, a urinary tract infection (UTI), also referred to as a bladder infection, is an inflammation in the urinary system. UTIs can occur in your kidneys, bladder, ureters, or urethra. They most commonly affect the bladder and urethra.

Pregnant women have an increased risk for UTIs, generally between weeks 6-24 of pregnancy. UTI’s can be caused because the increasing weight of the uterus, as it grows during pregnancy, can block drainage of urine to the bladder.

Symptoms of infections

When it comes to BV, having the infection upsets the balance of bacteria in the vagina. It can cause symptoms that include:

  • vaginal itching
  • unusual smell
  • vaginal discharge
  • burning sensation during urination

UTIs are generally painful. Common symptoms may include:

  • persistent urge to urinate
  • burning sensation during urination
  • cloudy or red urine
  • strong smelling urine
  • pelvic pain

It’s important to get tested for infection if you are experiencing any of these symptoms. Treating BV or UTIs will lower your risk of complications during pregnancy and help to prevent preterm labor.

How to test for infections

To test for BV, your doctor will likely perform a pelvic exam and may also take a sample of your vaginal secretions and the cells lining your vagina. Your doctor may also test the pH level in your vagina.

To test for a UTI, your doctor will take a sample of your urine to look for white and red blood cells or bacteria. If you have frequent infections, your doctor may perform a CT scan or MRI to look at your urinary tract to see if there are any abnormalities. Your doctor may also perform a cystoscopy by using a thin tube with a camera to examine your urethra and bladder.

Treatment and prevention

Pregnant women have a higher risk of contracting BV and UTIs than the general population. BV and UTIs are generally easy to get rid of with the help of antibiotics. However, any infections contracted or treated during pregnancy can cause complications for both the mother and the baby.

Because BV and UTIs can lead to premature birth and low birth weight, it’s recommended to get treated for infections as quickly as possible to avoid complications.

Sometimes BV will go away without treatment, and sometimes you will need antibiotics.

If you are prescribed antibiotics, it’s important to finish your treatment plan, even if your symptoms go away.

Creams and antibiotics in pill form are available to treat BV. However, even after treatment it can recur, typically within 3 to 12 months.

UTIs are also treated with antibiotics. If it’s a mild case, it will usually clear up in a few days. Your doctor may also prescribe a painkiller if you are experiencing severe pain in your bladder or when you urinate.


Be sure to get screened for infections as soon as you experience symptoms. Early detection and diagnosis will help you treat the infection quickly and help to reduce the risk of complications during your pregnancy.

You may also talk to your doctor about getting screened for infections even if you don’t have symptoms. Some infections are asymptomatic.

Antibiotics used to treat BV and UTIs are usually safe for most pregnant women. However, you’ll want to discuss any treatments for infection with your doctor. It’s important to understand the risks involved with taking antibiotics and the side effects you may experience while you are pregnant. Also, always tell your doctor about any allergies you have.

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