Treating Group B Strep: Are Antibiotics Necessary?

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By Christa Novelli
Issue 121, Nov/Dec 2003

Most women who have been pregnant in the last few years are familiar with the terms Group B Strep (for Group B Streptococcus), or GBS. The US Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) recommend that all pregnant women be screened between weeks 35 and 37 of their pregnancies to determine if they are carriers of GBS. This is done by taking a swab of the pregnant woman's vaginal and rectal areas. Studies show that approximately 30 percent of pregnant women are found to be colonized with GBS in one or both areas.^1-5

The CDC and ACOG advise all pregnant women who are found to be carriers of GBS to be treated with intravenous antibiotics during labor. Doctors and midwives have such great concern because GBS can be passed from the mother to the infant during delivery and can cause sepsis (a blood infection), pneumonia, and meningitis (an infection of the fluid and lining of the brain) in newborn infants. Therefore, most pregnant women who test positive for GBS choose to follow CDC and ACOG recommendations and attempt to avoid transmitting GBS to their newborns through treatment with IV antibiotics throughout their labors. Given all this, why would any woman choose not to accept IV antibiotics? But no woman can make a truly informed decision about this issue without taking a critical look at any recommendation that a third of all women and their infants be given antibiotics during labor.

GBS is a bacterium that normally lives in the intestinal tracts of many healthy people. A vaginal-rectal area colonized by GBS should not be termed "infected" any more than an intestinal tract colonized by GBS would be. GBS is a problem only when it is present in the genital area of a pregnant woman during labor and delivery. When this happens, there is a small risk that the bacterium will be passed on to the newborn infant, and that she or he will become sick as a result. Approximately 0.5 percent of women found to have GBS bacteria in their genital areas at 35 to 37 weeks into their pregnancies will go on to deliver a baby who becomes ill from GBS. This is 0.5 percent of women who receive no antibiotics during labor and delivery.

We should not take lightly the use of antibiotics for 200 women and their babies to prevent only a single blood infection-however serious that infection might be-especially in this age of increasing resistance to antibiotics. Concerns have arisen in several areas regarding the use of antibiotics for so many laboring women. One dilemma is that colonization of the vaginal area by GBS is, at best, a poor method of predicting whether a newborn will develop a GBS infection. As mentioned, even without any intervention during labor, fewer than 1 percent of infants born to carriers of GBS develop infections.^6,7

Some studies have shown a decrease in GBS infection in newborns whose mothers accepted IV antibiotics during labor, but no decrease in the incidence of death.^{8, 9} Still other research has found that preventive use of antibiotics is not always effective.¹⁰ In fact, one study found no decrease in GBS infection or deaths among newborns whose mothers were given IV antibiotics during labor.¹¹

Perhaps the greatest area of concern to medical researchers, as it should be to us all, is the alarming increase in antibiotic-resistant strains of bacteria. Antibiotic-resistant bacteria can cause infections in newborns that are very difficult to treat. Many large research studies have found not only resistant strains of GBS, but also antibiotic-resistant strains of E. coli and other bacteria caused by the use of antibiotics in laboring women.^12-21 Some strains of GBS have been found to be resistant to treatment by all currently used forms of antibiotics.²²

While many studies have found that giving antibiotics during labor to women who test positive for GBS decreases the rate of GBS infection among newborns, research is beginning to show that this benefit is being outweighed by increases in other forms of infection. One study, which looked at the rates of blood infection among newborns over a period of six years, found that the use of antibiotics during labor reduced the instance of GBS infection in newborns but increased the incidence of other forms of blood infection.²³ The overall effect was that the incidence of newborn blood infection remained unchanged.

The increase in other forms of blood infection among newborns is likely due to bacteria made drug-resistant by the overuse of antibiotics. Evidence exists that increased use of antibiotics frequently leads to increasing bacterial resistance. When a woman is given antibiotics during labor to treat GBS, the antibiotics cross the placenta and enter the amniotic fluid. While the antibiotics may have the desired effect of killing the GBS bacteria, some GBS bacteria can survive and become difficult, if not impossible, to kill with traditionally used antibiotics. Similarly, other bacteria, such as E. coli, that may be present in the mother or infant can become resistant to antibiotic treatment. These bacteria may not have presented a large risk of infection to the newborn until they were exposed to antibiotics and made into "super-bugs."

A study of 43 newborns with blood infections caused by GBS and other bacteria found that, when the mothers of the ill newborns had been given antibiotics during labor, 88 to 91 percent of the infants' infections were resistant to antibiotics. It is unlikely to be a coincidence that the drugs to which the bacteria showed resistance were the same antibiotics that had been administered during labor.²⁴ For the newborns who had developed blood infections without exposure to antibiotics during labor and delivery, only 18 to 20 percent of their infections were resistant to antibiotics.