What is the GBS test?

This test is done to detect the presence of the bacteria, group B streptococcus (GBS). GBS is not the same bacteria that cause strep throat, Group A Streptococcus. GBS bacteria are normally found in the vagina and/or lower intestine of 15 percent to 40 percent of all healthy, adult women. Being positive for GBS is usually not serious for a woman and is easily treated with antibiotics.

However, if you are pregnant, GBS is another matter. It has been identified as one of the main causes of life-threatening infections in newborn babies.

Why would I need a GBS test?

A woman can have GBS bacteria - often in the vagina, rectum or urinary bladder - and not know it. One way GBS can spread is through sexual contact. However, this bacteria usually does not cause genital symptoms or discomfort and is generally not linked with increased sexual activity. The GBS bacteria can affect the baby as it passes through the birth canal.

The Centers for Disease Control and Prevention recommends that all women get routinely screened for GBS during the 35th and 37th weeks of pregnancy. Mothers who are GBS-positive should be treated with antibiotics when labor starts in order to protect the newborn.

Women are at high risk to pass GBS on to their babies if they:

• Start labor before they reach 37 weeks' gestation (with or without ruptured membranes).
• Reach full term, but their membranes rupture and it seems as though labor will last more than 18 hours.
• Have an unexplained, mild fever during labor.
• Have already had a baby who had a GBS infection.
• Have or had a bladder or kidney infection that was caused by the GBS bacteria.

How is the GBS test done?

This is a simple and painless test done via a vaginal and/or rectal swab. After collection of surface cells, they are cultured in a lab. That is, cells are placed in a special solution to see if the bacteria grow. If the bacteria grow, that shows the woman has GBS. If no bacteria grow, then the woman does not have GBS.

What if I test positive?

If you test positive for GBS bacteria, you will be treated with antibiotics when you go into labor or if your water breaks early. If you are not tested, but you are thought to be at high risk for passing the bacteria on to your baby, you also be treated with antibiotics to eliminate the bacteria during labor and birth. Studies show it is not beneficial to give antibiotics during pregnancy, as in more than 65 percent of cases, the bacteria have time to regrow before labor begins.

All newborn infants are watched closely for symptoms of an infection, particularly if you are GBS-positive at some point in your pregnancy, whether you are treated with antibiotics or not. Chances are small that you can pass the bacteria on to your baby if you are treated with antibiotics right before labor. But, it can still happen. Babies who show signs of a GBS infection after birth are also treated with antibiotics.