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 Find out what other moms-to-be are asking. Join in the discussion with Henci Goer, an expert in obstetric research. If you would like to contact Henci outside of the Ask Henci forum, send an email to Goersitemail@aol.com.
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Topic: group b strep and broken waters? |
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Posted By on 20 Nov 2005 01:46 PM
Aimee,
I agree with everything Henci says and want to emphasize one more thing: early onset GBS disease in the newborn happens extremely rarely. Events that happen rarely are hard to study because you have to have huge populations (hundreds of thousands or even millions) in order to measure the effect of any given intervention. This usually takes a highly coordinated and well-funded study that involves multiple hospitals in order to reach the required number of study participants. When you look at a sub-population (i.e., all the women who break their water before labor), the task becomes even more difficult. So no doctor or midwife can quote accurate statistics about how likely the baby is to get sick in these specific clinical situations.
We will never know how effective it is to avoid unnecessary vaginal exams and internal monitors because there is no money to fund such a study (because there is no pharmaceutical company or other major player who'll benefit - other than mothers and babies!) and because these practices don't happen in most hospitals!
Thanks so much for your question.
Best,
Amy Romano, MSN, CNM
Editor, Lamaze Institute for Normal Birth By: Amy Romano |
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RE: group b strep and broken waters? |
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Archived User
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| 20 Nov 2005 06:46 PM |
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Aimee,
I agree with everything Henci says and want to emphasize one more thing: early onset GBS disease in the newborn happens extremely rarely. Events that happen rarely are hard to study because you have to have huge populations (hundreds of thousands or even millions) in order to measure the effect of any given intervention. This usually takes a highly coordinated and well-funded study that involves multiple hospitals in order to reach the required number of study participants. When you look at a sub-population (i.e., all the women who break their water before labor), the task becomes even more difficult. So no doctor or midwife can quote accurate statistics about how likely the baby is to get sick in these specific clinical situations.
We will never know how effective it is to avoid unnecessary vaginal exams and internal monitors because there is no money to fund such a study (because there is no pharmaceutical company or other major player who'll benefit - other than mothers and babies!) and because these practices don't happen in most hospitals!
Thanks so much for your question.
Best,
Amy Romano, MSN, CNM
Editor, Lamaze Institute for Normal Birth By: Amy Romano |
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Archived User
Posts:354
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| 19 Nov 2005 01:16 AM |
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Your post is kind of complicated, so I'm going to interweave my responses with yours.
"(Apologies if I'm asking about something you answered in Thinking Woman's Guide -- I read it when my now-5yo was in utero (and thanks to your info, I was confident in my choice to go for normal birth -- both she and her brother were normally and easily, as was her 3mo younger brother) and then gave my copy to another expectant mom. After this experience :-(, I think I'm going to buy copies for all of my expectant friends instead of just recommending it.)"
I'm glad you found my book helpful. As for your buying copies for your expectant friends, I'll drink to that! 
"I found data saying that women who are positive for group B strep have a 1/200 chance of infecting the baby if no IV antibiotics are used, and that the risk drops to 1/4000 if antibiotics are used. However, those numbers are only for women who give birth within 24 hours of their water breaking. I presume that's because no doctors are letting women go more than 24 hours. But where did this 24 hour deadline come from? I'm looking at the consensus guidelines (CDC/ACOG/etc) and it's all about *whether* and *when* *which* women should be screened and get antibiotics (which seems to be "wait 18hrs after PROM and then start abx," not "start abx immediately and insist upon delivery within 24hrs"), not about whether labor should be induced to reduce risk or whether deadlines should be imposed on women who have had premature rupture of membranes."
The CDC guidelines published in Aug 2002 say nothing about inducing labor in GBS positive women with ruptured membranes. The "24-hr rule" came out of some flawed studies in the 1960s. In point of fact, according to a large trial of induction vs. awaiting labor, infection rates do not go up over time in women with ruptured membranes if they are GBS negative, only if they are GBS positive. (Hannah ME, Ohlsson A, Wang EE, et al. Maternal colonization with group B Streptococcus and prelabor rupture of membranes at term: the role of induction of labor. TermPROM Study Group. Am J Obstet Gynecol 1997;177(4):780-5.) This, however, was back in the days before GBS positive women were treated with IV antibiotics in labor. Now that they are, the issue is rendered moot.
The CDC recognizes that GBS negative women are not at excess risk of infection. The guidelines state that IV antibiotics are not necessary in GBS negative women with ruptured membranes unless they have had a previous infected baby.
By the way, we do not know what GBS infection rates would be if clinicians kept their fingers out of the vaginas and and monitoring devices out of the uteruses of GBS positive women with ruptured membranes because we have no studies of which I am aware where vaginal exams and internal monitoring were avoided. The GBS organism comes from the rectum and is usually limited to the lower part of the vagina in colonized women where it is harmless to babies. It is possible that avoiding giving the bacteria a free ride on the examiner's finger or through internal EFM or contraction monitoring would be equally effective without the downside of antibiotic treatment. We'll never know because IV antibiotics do work, which leads to the question: If doctors had had antibiotics in Semmelweis' time, would they be washing their hands today?
"What exactly *is* the increase in risk if you let labor progress at its own pace? Also, what are the frequencies of the various adverse results from infection?"
As far as I can tell from the research, there is no excess risk in letting labor proceed at its own pace in a GBS negative woman or in a GBS positive woman provided she gets the proper number of doses of antibiotic over time. In fact, inducing labor might be counterproductive if her labor takes off like gangbusters.
"Also, while there are a lot of individual statistics, do you have a flowchart of what the risks for induction are that kind of sums it all up in one package? When the doctor says, "you have N% risk of harming the baby if you don't induce," is there a single number you can give that brings together the cascade of risks to the baby (from all downstream sources, in some sort of Bayesian thing) that arise if you *do* induce?"
Again, not as far as I know. What is available is information on the likelihood of infection based on factors such as whether the baby is preterm or the mother is lightly or heavily colonized.
(American College of Nurse-Midwives. Early-onset Group B strep infection in newborns: prevention and prophylaxis. Clinical Bulletin No. 2, 2003.)
Attack rate per 1000 live births:
GBS neg and no risk factors: 0.2
GBS pos and no risk factors: 5 [5 per 1000 = 0.5% = 1 in 200]
GBS pos and heavily colonized: 50
GBS pos and gestational age less than 28 wks: 28
Notice that 0.5% is a heck of a lot "less than 10%."
"Not that I want to counter one scare tactic with another, but the choice my SIL was given looked like, "serious risk (later forced to quantify to "less than 10%", which is true but massively misleading) of life-threatening infection if you don't induce, 0% risk of any adverse effects at all if you do induce" (if this were my doctor, I'd be writing a Very Strongly Worded Letter to the relevant authorities, because he flat-out *lied* about things like, "there is no increase in C-section rate with induction, that's a myth"), and she didn't know any better and trusted the doctor."
The medical research consistently finds that induction substantially increases the risk of c-section in first-time mothers. We know this from studies of elective induction, that is, induction for non-medical reasons such as convenience. This means that the increased surgery rate is due to the procedure itself, not any reason that might have led to the induction.
One of the huge problems in our current system is that medical staff can pretty much say and do anything without being called to account for their words or actions. Nonetheless, you might like to know that according to a Law Review article (Lent M. The medical and legal risks of the electronic fetal monitor. Stanford Law Rev 1999;51(4):807-37.), "a physician has a specific duty to 'keep abreast of progress' in her field . . . . Such duties obligate physicians to read, interpret, and apply the latest research regarding the drugs, techniques, and procedures employed in their specialties."
-- Henci
By: Henci Goer |
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Archived User
Posts:354
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| 16 Nov 2005 03:54 PM |
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Oy. Well, it's too late for this to do any good for my SIL, who just had a childbirth experience straight out of Thinking Woman's Guide in the "What you're trying to avoid" sections... but... I'm still curious to find out if there's any data that should have been used to guide her on-the-fly decision-making (or better yet, should have been given to her ahead of time).
(Apologies if I'm asking about something you answered in Thinking Woman's Guide -- I read it when my now-5yo was in utero (and thanks to your info, I was confident in my choice to go for normal birth -- both she and her brother were normally and easily, as was her 3mo younger brother) and then gave my copy to another expectant mom. After this experience :-(, I think I'm going to buy copies for all of my expectant friends instead of just recommending it.)
I found data saying that women who are positive for group B strep have a 1/200 chance of infecting the baby if no IV antibiotics are used, and that the risk drops to 1/4000 if antibiotics are used. However, those numbers are only for women who give birth within 24 hours of their water breaking. I presume that's because no doctors are letting women go more than 24 hours. But where did this 24 hour deadline come from? I'm looking at the consensus guidelines (CDC/ACOG/etc) and it's all about *whether* and *when* *which* women should be screened and get antibiotics (which seems to be "wait 18hrs after PROM and then start abx," not "start abx immediately and insist upon delivery within 24hrs"), not about whether labor should be induced to reduce risk or whether deadlines should be imposed on women who have had premature rupture of membranes.
What exactly *is* the increase in risk if you let labor progress at its own pace? Also, what are the frequencies of the various adverse results from infection?
Also, while there are a lot of individual statistics, do you have a flowchart of what the risks for induction are that kind of sums it all up in one package? When the doctor says, "you have N% risk of harming the baby if you don't induce," is there a single number you can give that brings together the cascade of risks to the baby (from all downstream sources, in some sort of Bayesian thing) that arise if you *do* induce?
Not that I want to counter one scare tactic with another, but the choice my SIL was given looked like, "serious risk (later forced to quantify to "less than 10%", which is true but massively misleading) of life-threatening infection if you don't induce, 0% risk of any adverse effects at all if you do induce" (if this were my doctor, I'd be writing a Very Strongly Worded Letter to the relevant authorities, because he flat-out *lied* about things like, "there is no increase in C-section rate with induction, that's a myth"), and she didn't know any better and trusted the doctor.
--Aimee
By: aimee |
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