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Fruit of the Womb
Fruit of the Womb

Urinary Tract Infections with Group B Streptococcus (GBS) During Pregnancy

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The following comment was recently left on my previous post "Misunderstanding Group B Streptococcus (GBS)":

Hi - I am getting a little confused about Group B Strep (GBS) and UTI (urinary tract infection) information. Hoping you can help me clarify. I am 7 weeks pregnant and was just diagnosed with a UTI with GBS (asymptomatic - it was done as part of my first visit screen). The nurse called and wants me to start ampicillin (5oo mg 4x/day for 7 days) immediately. I have currently taken no medication (not even a tylenol) during this pregnancy (my first). I keep reading that GBS does not require treatment but then saw that it may with a UTI - I did not know symptomless UTI's were possible. I am very much wanting to not take any medication - your thoughts on this are greatly appreciated.

One of my very first posts here at “Fruit of the Womb” addressed Group B Streptococcus (GBS) infections and pregnancy. This is a topic that is worth revisiting periodically and the questions from today’s reader raise concerns that are shared by many women during pregnancy.

GBS is a bacterium that colonizes the urogenital and lower gastrointestinal tracts in as many as one-third of all healthy reproductive age women. It is the leading cause of serious bacterial infection in newborns and is often transmitted to babies at the time of delivery. Indeed, 8,000-12,000 babies per year in the U.S. will develop complications related to GBS and approximately 2,000 infants will die from their infections. There are several well-known situations in which babies are at increased risk for developing a serious GBS infection including:

Premature labor or rupture of membranes before 37 weeks
• Prolonged rupture of membranes (18 hr or longer) before delivery
• Fever in labor (100.4F or higher)
• History of GBS urinary tract infection during the pregnancy (4-fold risk)
• Previous baby affected by GBS disease (increases risk 10-fold!!!)


Today’s reader had an asymptomatic UTI with GBS detected at her first prenatal visit during routine screening. We do NOT know why some people carry GBS and others do not, and we are not entirely clear why far more women actually carry the bacterium than are at risk for having a baby with a serious complication related to it, although the maternal immune response to the bacterium probably plays a key role. However, we do know that GBS UTIs place women in one of the highest risk categories for pregnancy complications (preterm labor; premature rupture of membranes; subclinical premature cervical change in the continuum of ‘cervical incompetence’; chorioamnionitis) and for transmission of GBS to the baby at the time of delivery and even prior to the onset of labor (CDC, MMWR May 31, 1996;45:1-24 ). Interestingly, women with GBS UTIs are also at greater risk for hypertensive disorders in pregnancy, anemia, and for babies that are not only premature, but ‘small for gestational age’ (Schieve, et al., Am J Public Health 1994;84:405-410).

UTIs caused by GBS occur in about 5% of women. Many women are asymptomatic or confuse symptoms of pregnancy with subtle symptoms of urinary tract infections (pressure; suprapubic discomfort; frequency; and urgency). However, asymptomatic UTIs can still subject the pregnancy to the risks of the complications mentioned above. Even after treatment, asymptomatic or symptomatic UTIs will recur in as many as one-third of all pregnant women. The source of the ‘reinfection’ is usually the patient’s own lower gastrointestinal tract in which antibiotic therapy of the UTI is ineffective at eradicating colonization. Women with GBS UTIs are usually considered to be more heavily colonized and are at greater risk for persistent and recurrent GBS infections (CDC, MMWR August 16, 2002;51:1-22). They are also at greater risk for developing significant bladder and kidney infections (pyelonephritis), the latter of which may occur in as many as 50% of women who begin with an untreated ‘asymptomatic’ UTI and can be life-threatening, leading to sepsis, adult respiratory distress syndrome (ARDS), and even death during pregnancy. It is the current recommendation that women with symptomatic or asymptomatic GBS UTIs detected during pregnancy should be treated at the time of diagnosis (CDC, MMWR May 31, 1996;45:1-24).


There are 5 major serotypes of GBS (Ia, Ib, II, III, and V). All are capable of causing both maternal and neonatal disease. Babies born to women who do not have antibodies to types II and III seem to be at greater risk for complications. Indeed, at some point, this may be one of the primary factors we can use to differentiate pregnancies at risk from those which are less so. A recent study has shown that serotypes V, Ia, and III are most often associated with asymptomatic and symptomatic UTIs (Ulett, et al., J Clin Microbiol. 2009;47:2055-60). About two-thirds of serious GBS infections are apparent at the time of delivery and 90% of babies who will develop complications do so within the first 48 hr after delivery. This is generally referred to as “early-onset” GBS infection and technically is used to define disease occurring in the first week of life. “Late-onset” disease, frequently associated with serotype III, affects another 10% of newborns, often presents as meningitis with septicemia, and rarely occurs after one month of age. Up to one-third of the survivors of GBS meningitis will develop long-term physical and/or neurological handicaps and in 1 of every 8 of these babies, the handicaps will be severe.

Unless you are in one of the high risk groups noted above, the goal of prophylactic antibiotic therapy during labor in those who are found to be colonized with GBS during their pregnancies is to deliver antibiotics to the mother early enough in the course of labor that sufficient drug can be transferred across the placenta to achieve protective levels in the baby prior to birth. That means, the antibiotic selected must not only be able to kill GBS, but it must also be able to cross the placenta. Fortunately, GBS has not yet been found to have developed resistance to the antibiotic of choice, penicillin G, and this drug also readily crosses the placenta. It also has a long and proven safety record for the baby. Ideally, antibiotic therapy is begun, intravenously, at least 4 hr prior to delivery so that at least one or two doses can be administered before the baby is born. If a woman has a serious allergy to penicillin, other options for therapy exist and the risks and benefits of these are discussed in our previous post on this subject.

The important things are that your doctors did the right thing by screening you, they have identified a potential problem, and there is a well-proven means of significantly reducing the risks from that problem for both you and your baby during your pregnancy and at the time of your labor and delivery. Thanks for reading and for the good questions. Best wishes for the rest of your pregnancy!
Dr T
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