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. Infection can cause premature labor. Some newborns may develop physical or intellectual disabilities if infections are not addressed or the baby is born early.

Infections in pregnancy

Any infection can lead to rupture of membranes and preterm labor. More than 12 percent of infants born in the United States are premature. Forty percent of those births are associated with infections.

If a pregnant woman is exposed to infectious agents during pregnancy, the consequences to the fetus can be dire and even life-threatening. Intrauterine infections get to the baby through the mother’s blood and across the placenta. Intrauterine infections can be caused by rubella (German measles), toxoplasmosis (from cat feces), or herpes virus. All of these congenital infections are dangerous to a growing fetus. Syphilis is another example of a congenital infection.

Serious infections can also enter the uterus through the vagina if there is a vaginal infection or a urinary tract infection (UTI). Vaginal infections (bacterial vaginosis or BV) and UTIs can lead to infections within a pregnant uterus. These are commonly E. coli, Group B strep, or other bacteria. While adults can recover from infections of Group B strep (for example), the consequences to the baby are serious. The ascent of a bacteria or virus through the vagina will ultimately infect the amniotic sac and fluid. Rupture of the sac and premature labor and delivery follow.

About 10 to 30 percent of pregnant women contract BV during pregnancy. It’s the result of an imbalance of the normal bacteria in the vagina. It isn’t a sexually transmitted infection, but it’s 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 American Pregnancy Association, a 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. The increasing weight of the uterus, as it grows during pregnancy, can block drainage of urine to the bladder. This can cause a UTI.

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’re 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

Get immunized against rubella before you get pregnant or immediately after you deliver.

Pregnant women should never handle cat feces and litter boxes.

On your first prenatal visit with your doctor or midwife, you will be screened for many existing conditions. Ask questions about the tests performed. Blood work and vaginal swabs are performed to rule out many conditions.

You will be tested for Group B strep with a vaginal swab later in pregnancy, so don’t miss your regular prenatal care appointments.

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

If you’re prescribed antibiotics, it’s important to finish your treatment plan, even if your symptoms go away. UTIs are also treated with antibiotics. If you have a mild case, it will usually clear up in a few days. Continue taking the antibiotics until you are finished with the prescription. The doctor will have chosen an antibiotic that is safe in pregnancy. Your doctor may also prescribe a painkiller if you are experiencing severe pain in your bladder in general or when you urinate.

Intrauterine infection can lead to abnormalities or illness in the newborn, premature birth, or low birth weight. Therefore, it’s recommended to get treated for infections as quickly as possible to avoid complications.


Be sure to get screened for infections in your first prenatal visit or 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.

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

Make sure the doctor treating you for the infection knows you’re pregnant. 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.