Postdates: Separating Fact from Fiction
Saturday, October 3, 2009 at 7:53AM A guest post by Birthkeeper (Christine Fiscer)
What is one of the first things that a pregnant woman hears once she reaches 40 weeks?
“When will your doctor induce you?”
Is there evidence behind this practice to support the routine induction of pregnancies that go beyond 40-41 weeks? What are the usual assumptions and beliefs surrounding this?
• There is a higher risk of the baby being born still
• The placenta will stop functioning
• There will be a decrease in amniotic fluid
• The baby will grow too large
We are going to take a look at the validity of these claims and beliefs, and compare them with what the research has to say. After all, your doctor would never do anything that wasn’t in your or your baby’s best interest, correct?
The first things to really look at are the definitions of the two key words with the pregnancy that goes past 40 weeks. Postdates, and Postmaturity. But is it accurate to start with these terms at 40 weeks?
• Postdates – Defined as a pregnancy that goes beyond 42 weeks, based on LMP. The problem with this is that it’s not the same for every woman. Due dates are calculated depending on LMP, but does not usually take into account a woman who has shorter or longer than 28 day cycles. The pregnancy wheel that is commonly used by doctors and midwives, is based on 28 day cycles. If you have a longer cycle, days will need to be added to your EDD ( Estimated Due Date ). This is rarely done however, and women who have longer cycles are held to the same due date estimation as women with shorter cycles. So on paper, you might be 42 weeks according to the estimated due date, when in actuality you would only be 41 weeks. A more accurate way of dating pregnancy is by solidly known conception dates.
• Postmaturity – Postmaturity, or Postmaturity Syndrome (PMS) can only be diagnosed after delivery and is defined as a postdates pregnancy accompanied with a combination of the following newborn assessments:
a) No lanugo ( fine body hair )
b) Long nails
c) Abundant hair on head
d) Calcified fetal skull
e) Hanging or wrinkled skin, with the appearance of weight loss
f) Dehydrated
g) Peeling skin
Postmaturity Syndrome also only affects less than 10% of pregnancies that go beyond 43 weeks. The vast majority of pregnant women do not go beyond 42 weeks with correct dates. Some studies show that less than 3% of women go beyond 43 weeks. So if the risk of postmaturity is less than 10% of pregnancies that go beyond 43 weeks, and the percentage of women who go beyond 43 weeks is less than 3% - how big of a risk is it really?
The problem with assessing risk for postmaturity is that modern Obstetrics, and even modern Midwifery, tends to treat all women as equal in pregnancy. Seldom is personal or familial gestation history taken into account, or abnormal cycle and ovulation schedules. These things are important to consider! How healthy would a midwife’s policy of inducing at 41 weeks , be for a woman who has a personal or familial history of going to 44 weeks? We are talking about potentially trying to induce a baby who will be 3 weeks “early” according to their own biological gestation clock. And if the induction “fails”? It will likely result in stress for both mother and baby and lead to more invasive intervention, and possibly a cesarean.
The condition of a baby and placenta all depends on the health and personal history of the mother, as well as the health of the baby – at any gestation. A placenta does not begin to deteriorate automatically beyond 42 or 43 weeks. A placenta can begin to deteriorate at 36 weeks, once again, depending on the health and over all well being of the mother and baby. I have often heard the fear in women of “placental deterioration” after 40 weeks. But as it has been seen, this has nearly nothing to do with length of gestation, as much as it has to do with overall health and maturity of the individual pregnancy and baby. I personally have seen a baby born at 43 weeks, solid dates, absolutely covered in vernix and attached to a very healthy placenta. In contrast, I attended the birth of a 37 week baby who had dry, wrinkly skin, and a calcified and very old looking placenta.
Other important factors include unhealthy habits and complications such as:
• Smoking
• Alcohol
• Drugs
• Diabetes ( Mellitus, NOT Gestational )
• Hypertension
When did 40 weeks become the magical number?
The interesting part in the discussion of postdates, postmaturity, and all that it involves, is the thought that 40 weeks is some sort of magical number. In the past, there was a general “due month”. Women were given an estimation of when they would deliver, based on the known fact that normal gestation is anywhere from 37 to 42 weeks. So when did 40 weeks become this magical number that women fret over and worry once they go beyond it? It has always been that 40 weeks is the general time frame when babies were “due”. But it wasn’t until a study by McClure-Brown came out with date collected from 1958, that showed the perinatal mortality rate doubled from 40 weeks to 42 weeks – from 10/1000 to 20/1000. So it might be logical to assume that inducing labor before 42 weeks would cut back the risk of stillbirth, correct?
The problem is, this study is inaccurate and too old to continue to be of use. Modern obstetrics contradicts the findings in the study published in 1963. And yet, the findings continue to be cited. If we accepted the outcomes in the McClure study, we would also have to accept a 10/1000 mortality rate at 40 weeks! And we know that is not correct. We know that in the 1950s, the majority of women were put under general anesthesia, or twilight sleep, and forceps were commonly used.
Modern obstetric research actually shows there to be not much of a difference in perinatal mortality rates between 38 and 42 weeks, with a decline in between.
An identically set-up chart to the 1963 study, published in 1982 ( Williams, Creasy ) reads:
• 7/1000 at 38 weeks
• 6/1000 at 40 weeks
• 8/1000 at 41 weeks
• 9/1000 at 42 weeks
• 10/1000 at 43 weeks
• 11/1000 at 44 weeks
A graph from 1987 statistics ( Eden, Sefert ) shows:
• 6/1000 at 38 weeks
• 2/1000 at 40 weeks
• 2.3/1000 at 41 weeks
• 3/1000 at 42 weeks
• 4/1000 at 43 weeks
• 7/1000 at 44 weeks
So according to the second set of statistics gathered above, women were at higher risk of stillbirth at 38 weeks, than they were at 42. Interesting! In the first set, there was only a steady increase, resulting in a very small risk increase. Is the slightly increased risk worth the myriad risks that come with labor induction?
A large study done by Weinstein, et al. , compared nearly 1,800 reliably dated post-term pregnancies with a matched group of on-time deliveries ( between 37 and 41 weeks ). The outcomes were surprising. Perinatal mortality was similar in both groups ( 0.56 / 1000 in the post-term and 0.75 / 1000 in the on-time group ). The rates of meconium, shoulder dystocia, and cesarean were almost identical. What was most interesting, however, was that the rates of fetal distress, instrumental delivery and low Apgar scores were actually lower in the post-term group than in the on-time group.
What about the Amniotic Fluid?
There is a flawed belief that the amniotic fluid will somehow begin to “run out” beyond 40 weeks. There is a belief that women will have a “dry” birth. Let’s start with some basics.
What is amniotic fluid?
• Beyond 36 weeks, amniotic fluid is comprised of mostly fetal urine. When the baby’s kidneys are functioning properly, the baby will continuously produce and process amniotic fluid. The fluid is swallowed by the baby, and then urinated out, once processed by the kidneys.
As long as the mother is adequately hydrated, and there are no congenital abnormalities in the baby, the baby will continue to create amniotic fluid until birth. Whether this be at 37 weeks, or 44. If decreased amniotic fluid is suspected through palpation, an ultrasound can be done to measure the volume found. However, this is not an exact science, as the volume found can – and usually will – vary from ultrasound technician to ultrasound technician, and can also sometimes be dependent on baby’s position. If the levels are found to be on the low side, evidence based protocols suggest having mom orally re-hydrate and return within 24 hours for another AFI ( Amniotic Fluid Index ), preferably by a different technician. This has shown repeatedly to have improved outcomes, versus immediate induction for low AFI levels.
A study published in the Journal of Reproductive Medicine found a significant increase in amniotic fluid after maternal oral rehydration, as well as intravenous hydration, with neither one better than the other. In all, 62.5% and 44.0% demonstrated improved AFI levels.
What if the baby grows too large?
First, who defines “too large”? What is “too large” for one woman, might be the next woman’s smallest baby size. The most important thing to remember is that there is no fool proof way of knowing whether or not your body can naturally birth a baby of whatever size, until you have tried. Ultrasound has a 20% error rate in either direction, and many women have allowed an induction after being told that their baby would be nearly 10 pounds, only to give birth to an 8 pound baby. And, there is no reason for a woman to doubt her ability to birth a 10 pound baby unless she tries. I, for one, never would have believed that I could have birthed my nearly 11 pound baby, especially because I was told that I could not safely birth my 8 ½ pound baby that I was scared into a cesarean with. You never know until you give it a full chance.
Women are often told that a baby will gain approximately a ½ pound per week in the end of pregnancy. However, this is simply an approximation. Once again, this is NOT the same for every woman, or for every baby.
According to a fetal growth rate chart comprised by four studies , a baby will only put on approximately 0.56 pounds – that’s just over half of a pound – between 40 weeks and 43 weeks. And since we’ve shown that most women go into labor before 43 weeks, it can be assumed that it is even less than that. Babies hit a plateau with weight gain around 40 weeks. So really, is there a huge concern to be had over a baby being birthable at 40 weeks, but not at 42 if we’re talking about less than half of a pound? And, does less than half of a pound change the shoulder width or head size of a baby? Hardly. It may give baby chubbier cheeks, or chubbier buns, but will not change the overall structure of the baby, making baby automatically “too large” to birth between those two weeks.
When Should Monitoring a “Post Dates” Pregnancy Begin?
This may be different for each individual pregnancy, each individual woman, which makes cookie cutter policies surrounding post dates, arbitrary. To begin, we have now shown that according to research, doctors, and all basic “rules” that a pregnancy is not even considered postdates until after 42 weeks. Not 40. So if the pregnancy is not postdates until 40 weeks, why do doctors often begin Non-Stress Tests ( NSTs ), Biophysical Profiles ( BPPs ), and Amniotic Fluid Index ( AFI ) at 40 weeks? It goes back to the very flawed study from 1963.
It is up to each individual woman to decide if she is comfortable waiting on monitoring, but if a woman understands that there is virtually no risk difference from 38 weeks to 42 weeks, it should clarify that testing before 42 weeks is mainly unnecessary unless other pregnancy complications are present (i.e. Hypertension, Diabetes Mellitus, IUGR suspicion, Congenital Abnormalities ).
So, let’s take a look at what type of monitoring is available, and how effective they are in finding possible problems.
• Biophysical Profile ( BPP ) – A BPP checks fetal body tone, fetal movement, amniotic fluid volume, and fetal “breathing” practices. Each of these are given a score, and then it is added up to give an overall score. A high score of 8-10 usually shows a baby in good health, while a baby who scores 0-4 indicates a baby who needs to be more closely monitored, or needs to be outside of the womb. Scores in between will usually come with more monitoring, including another BPP within 24 hours.
According to Enkin et al., in A Guide to Effective Care in Pregnancy:
There is some evidence that these tests can detect pregnancies in which there is ‘something wrong,’ but less evidence that their use improves outcome, or can eliminate the additional risk of post-term pregnancy. The only controlled trial shows no advantages of complex fetal monitoring with computerized cardiotocography, amniotic fluid index, assessment of fetal breathing tone, and gross body movements over simple monitoring with standard cardiotocography and ultrasound measurement using maximum amniotic fluid pool depth.
So as you can see, even the detailed testing may not prevent issues that may arise.
According to several studies that researched the accuracy of the BPP, the false positive rates were quite high, resulting in unnecessary induction or further monitoring.
One in particular showed a 21.3% false positive rate for the BPP, and a 39.3% false positive rate for the Non-Stress Test ( NST ). More studies have shown much higher false positive rates for the Non-Stress Test, which is the most common for women who go beyond 40 weeks in care under an Obstetrician.
• Amniotic Fluid Index ( AFI ) – An AFI is basically a mini Biophysical Profile. It measures the maximum amniotic fluid pool depth in the uterus. However, as was shown in the beginning of this article, the AFI in a pregnancy can be contingent on several factors. Being dehydrated can lessen the AFI found. The baby’s position can affect how much amniotic fluid is seen. The skill of an ultrasonographer can make a difference in the AFI level found.
It was also shown that AFI levels can be improved with maternal oral rehydration. Often in modern obstetrics, this protocol is ignored, and induction is recommended very much against proven evidence.
• Non-Stress Test ( NST ) – The NST is the most commonly used test with women who go beyond 40/41 weeks pregnant, under the average Obstetric care. An NST is electronic fetal monitoring for contractions, fetal heart rate variability, and overall heart rate strength. If a baby is found to be sleeping, stimulation is often used in the form of vibration, a cold drink with sugar ( such as orange juice or soda ), or palpation stimulation.
The NST comes with the highest false positive rates of all of the tests, which is why it has become a controversial test amongst some groups.
Studies have been done that conclude anywhere from a 50%-75% false positive rate on average, sometimes reaching as high as 80-90%. False positives will lead to more testing, more stress, and possibly unnecessary intervention in the pregnancy.
Conclusion
Facts:
• A pregnancy is NOT “Postdates” until after 42 weeks.
• The risk of stillbirth is nearly a flat line between 38 weeks and 43.
• Amniotic fluid is dependent on maternal hydration, in the absence of congenital abnormalities.
• A baby’s weight virtually plateaus after 40 weeks.
Some things to think about :
• If I am not “overdue” until after 42 weeks, should I allow testing or intervention before this point?
• If NSTs come with very high false-positive rates, is it a test worth submitting to?
• If my baby will not put on much weight within a 3 week period, is it logical to worry about my baby being “too large” within a probable 2 week period?
Please, please always do your own research. Question what you are told - and go study the subject – regardless of whether your OB, midwife, family member or friends are the ones giving you the information. Make informed decisions, and take charge of your prenatal care!
Christine Fiscer is a Traditional Midwife who blogs at www.midwiferyramblings.blogspot.com and also www.joyfulbirthservices.blogspot.com. She enjoys all things birth, sewing, and spending time with her family.
_______________________________________________________________________________________
McClure-Browne, J.C. 1963. Comparison of perinatal mortality rates versus gestational age through the past three decades. Postmaturity, Am J Obstet Gynecol 85: 573–82.
Journal of Fetal Medicine 1996 Sep-Oct. 5(5): 293-97. Expectant Management of Post-Term Patients: Observations and Outcome. Weinstein D. et al.
Journal of Reproductive Medicine 2000 volume 4 pp 337-340. Effect of Oral and intravenous hydration on oligohydramnios. CHANDRA P. C.; SCHIAVELLO H. J. ; LEWANDOWSKI M. A. ;
(1)Doublet PM, Benson CB, Nadel AS, et al: “Improved birth weight table for neonates developed from gestations dated by early ultrasonography.” Journal of Ultrasound Medicine. 16:241, 1997.
(2)Hadlock FP, Shah YP, Kanon DJ, et al. “Fetal crown rump length: Reevaluation of relation to menstrual age with high resolution real-time US Radiology.” 182:501, 1992.
(3)Usher R, McLean F. “Intrauterine growth of live-born Caucasian infants at sea level: Standards obtained from measurements in 7 dimensions of infants born between 25 and 44 weeks of gestation.” Pediatrics. v.74, 1969.
(4)Wigglesworth JS. Perinatal Pathology, Second Edition. W.B. Saunders Company. 1996. page 24.
Hassan S. Kamel, Ahmed M. Makhlouf, Alaaeldin A. Youssef. Gynecol Obstet Invest 1999; 47: 223-228
Evertson LR, Gauuthier RJ, Schifrin BS, et al., Antepartum fetal heart rate testing. I. Evolution of the non-stress test. Am J Obstet Gynecol 1979;133:29-33
Miller, David A MD; Rabello, Yolanda A MSEd; Paul, Richard H. MD. Americal Journal of Obstet and Gynec. 174(3):812-817, March 1996.
View Printer Friendly Version
Email Article to Friend
Reader Comments (26)
Great article, thanks! :)
Very good info! I didn't know postdates was 42 weeks. I wouldn't automatically call any pregnancy past 40 weeks postdates, but it's something I've heard assigned to babies who are obviously very "well cooked." My midwives said Jacob was postdates, even though I knew the exact date of conception and the ultrasound confirmed it. He was dry and peely and wrinkled, long clawlike fingernails, no lanugo at all, and I never saw any vernix on him but he was a waterbirth so it might have washed off. They put him in their records as "41+ weeks", so not sure if he really qualifies as postdates after all now. Still very interesting post! This should be standard reading for all women once they "go over!"
Oops, I meant to add that he was 39w6d, so he wasn't actually "overdue" at all.
This is GREAT information. Bookmarking so I can pass it along. If there's anything that makes me so mad I could spit, it's the idea that it's "safer" to induce at 38 weeks than to let the body begin labor on its own. I would just love to sit down with an induction-happy doc and ask him to give me a list of reasons it's better for mom's and baby's health to force the body into labor.
The induction epidemic really got going when a study was done by Hannah et al in 1993 which showed that outcomes could be improved (very slightly) by inducing all women at 41 w.g.a. The study was flawed in its methodology but this was not discovered until years later. I have posted the denunciation of that induction recommendation on my blog at
http://www.glorialemay.com/blog/?p=116
Gloria
@Gloria (or anyone else who knows), has *any* Hannah study not been eventually shown to be deeply flawed, and ultimately unusable (or nearly so)? It seems that the studies that were used to force all mothers of breech babies to undergo Cesareans, and to force "elective" repeat C-sections due to the fear of VBAC were Hannah studies. Am I remembering right?
Also, stillbirth & perinatal mortality are different terms. I'm not sure if that makes any difference, though. The definition of "perinatal mortality" has changed a bit, I think, in the past few decades, so that it now includes the fetal demise of any baby beyond 20 weeks all the way through 7 days post-birth. When you talked about the high stillbirth rate at 38 weeks, I was reminded of one study on twins I read, in which it *appeared* that the risk of stillbirth or IUFD increased later in pregnancy (after 36 weeks, I think), but often what happened was that one of the babies would die earlier in pregnancy, so they would wait until the surviving twin had gestated longer, and then induce. The actual time of death was several weeks earlier, but because the babies weren't *born* until 36 weeks (or whenever), it looked like there was this huge jump in stillbirth at 36 weeks. It may be that some of the high stillbirth rate at 38 weeks was due to that -- that the baby would die earlier, and the woman may not have been induced earlier, but waited until labor started naturally; or the woman may have been induced at 38 weeks, when her cervix was favorable.
This was an excellent article! I had a c-section after a failed induction at 42w5d. I want to VBAC with the next baby (which I'm not pregnant with yet) and am concerned I might just be a long breeder. I definitely don't want to be induced! This article is a great resource for me. Thanks!
EXCELLENT article. I wish I would have read something like this before I went in for being induced for "postdates" as I was ESTIMATED (long irregular cycles) for being about 40w 6d.
This was a fabulous article. Very informative and concise. I wish more women would question and research as thoroughly as this. Too many people believe their PCG to be unfailingly accurate and unbiased.
It took me three pregnancies to figure out that my cycle is just longer than other women and that meant my babies needed to "cook" longer. NONE of my babies was born before 41 weeks, and my third was born at 42w3d.
I sometimes wonder about whether I was even in labor when I went to the hospital to have my first son. I wasn't sure if it was really "it," so I went to the hospital to have them tell me. They said I was in labor, but immediately started me on pitocin. So now I ask myself, if my contractions weren't "strong enough" or "regular enough," and I wasn't dilated "far enough," what was their criteria for determining that I was in labor? That I was 41 weeks along?? If I had gone to bed instead of the hospital, would I have woken up still pregnant and had my baby days or weeks later? Could I have avoided the pitocin that led to the epidural that led to the c-section?
Kathy: the breech one was, I think. Studies that supposedly 'showed that elective cesarean is safer than VBAC are numerous and Henci I think debunked them all.
Great post!
I knew the date of conception for my daughter. Unfortunately, my midwives never noted this in my chart and when I started labor at 37 weeks (really 38 weeks for me) it was a big scare for them. My labor ended up stalling and I had a very slow progression over two weeks. During that two weeks we just waited. I went from 0-80% effacement during that two weeks and went from 0cm dilated to 5 cm dilated by the time I started active labor. I ended up having 6 hours of hard labor total. My midwives noted my daughter being born at 38wk1d and by my calculations based on the known date of conception I was exactly 40 wk when I delivered my baby. 40 wks happened to be my number but using that wheel had me measured too early. If my daughter had been a little overdue, my midwives would have that she was on time. Estimating delivery dates is not an exact science, I wish more people would just let labor start naturally. I have a friend that was born 3 months past his due date in Ireland where they don't rush this sort of thing. He was born around 9 lbs and was 23 inches long, born vaginally with no complications. He attributes his late birth to the fact that his mother was prone to miscarriages and may have gotten pregnant after a miscarriage and thus she missed her period for 3 months prior to her actual pregnancy with him. Can you imagine if she'd been forced to deliver at 6 months because they thought she was 42 weeks along? Tell me that wouldn't have resulted in a stillbirth as this was almost 40 yrs ago. Even today a 28 week old has a very slim chance of surviving even with NICU care. If they are so worried that can do heart rate doppler checks every few days to check on baby's health. Fetal movement counts could be a good way of keeping track of baby's health. Why rush based on a roulette wheel?
“When will your doctor induce you?” is right up there with "will he let you go past your due date?"
let you? er, if your permission slip is notarized on an odd tuesday in months beginning with a "J".
why the bleep have women agreed to give our power away???
fabulous article/post. it reminds me of Gail Hart's "Induction and Circular Logic" article published in Midwifery Today issue #63.
This is fabulous! I wish all pregnant women would read it! Thank you.
I was supposedly a month late. My brother was late too, both of us were 6 lbs babies. I had my son at almost 42 weeks, after an induction (77 hours!). He just wasn't ready. :) I am currently pregnant and WILL NOT be induced. Luckily, Oregon does not call DHS on mom's who refuse to be induced. I checked. Thank you for all your valuable info and for helping me to realize my body was made to do this!
Thank you for posting this. According to my doctor, my due date is March 9. However, based on my own calculations (I was charting, so I know what day I ovulated) I won't be due until 2 weeks later. It's good to have this info because I'm already preparing to fight them on induction when I go "late" according to their timeline, not reality.
Fantastic article.
My 2nd son was born at 43 weeks to the day, 9.5lbs and PERFECT. There was vernix in the waters, no signs of postdates other than a touch of very normal, and harmless, meconium.
I have a theory about the fluid levels and labour, which I've been studying since after my first son was born (and died).
My first son had bilateral renal agenesis: no kidneys. This resulted in a huge reduction in amniotic fluid as he lacked the ability to create urine (while he had a bladder, it had no connections and was effectively "Floating" around). Babies with his condition do not continue gestating past 35 weeks; almost all labours begin naturally by that point except a rare few (and even then it's generally not by much... no one goes 44 weeks, that's for sure).
I went into natural labour at 34 weeks to the day, and never once felt he was 'premature'. While that's anecdotal and not substantial to my point, I felt it important to mention: he just wasn't. It was his time. Labour was quick, painless and easy up until my forced cesarean when they found him crowning breech.
Apparently in babies with severe kidney malformations (and missing kidneys in particular) where fluid levels are dangerously low, labour is always "early".
There is apparently also a natural reduction in amniotic fluid levels as you go post dates in a 'normal' pregnancy, though generally this is seen as an emergency due to the fact that persistent low fluid is usually associated with kidney problems. However, the reasoning behind this hysteria doesn't make any sense: the pressure (and thusly compression) that comes with severe oligohydramnios does indeed cause internal organ damage - but it is cumulative. This pressure damage happens over a long period of time during early developmen when the organs are particularly vulnerable. It's not as though a random drop in fluid levels at 42 weeks is going to cause heart problems two days later. That's just not how it works.
If there has been no other signs of kidney problems, why the hysteria? What's the point? Plus: even if there had been undetected kidney issues and the oglio WAS a symptom - and I hate to put it so bluntly - but the damage is done!
Inducing my son's labour 6 weeks ahead of time wouldn't have saved his life: what's done is done, and it was done by 25 days past conception.
We still don't know precisely what chemical reaction begins natural labour... could it be that a decline in fluid levels are part of the catalysts that tell our bodies that our baby is ready? I think so. While I have no real proof yet (nor does anyone, really) it is a theory I feel strongly about. :)
Cheers.
I am a labor and delivery RN and I found this article to be very informative. I believe that in general, there are way too many "elective" inductions or inductions for "post-dates" at 40 weeks being performed in L&D units today. The body is meant to birth on it's own clock; unless there is a valid medical indication for induction, I feel induction is often uneccesary and can even cause complications.
There is one piece of this article that I do not quite understand regarding the NST. NSTs are performed to assess fetal well being via assessment of the fetal heart rate and the fetal response to the possible presence of contractions. Sleep cycles are normal in fetuses and are tolerated for 20 minutes, but more commonly the ""stimulation" is simply maternal position change. The NST is determined reactive and reassuring based on variablity of the heart rate, presence of accelerations of the heart rate (2 or more in 15 minutes), and the absence of "late decelerations" associated with contractions.
I have never heard the term "false positive" used before in relation to an NST. What exactly does that refer to? False positive for what? The result of an NST is either "reassuring and reactive" or "non-reassuring." Does this mean that the writer is talking about an NST reading as "non-reassuring" when the fetus is, in fact, just fine? I acknowledge that fetal heart monitoring is overused and is subject to interpretation, but I find it hard to believe that 50-90% of NSTs are read as falsely being non-reassuring.
"Non-Stress Test ( NST ) – The NST is the most commonly used test with women who go beyond 40/41 weeks pregnant, under the average Obstetric care. An NST is electronic fetal monitoring for contractions, fetal heart rate variability, and overall heart rate strength. If a baby is found to be sleeping, stimulation is often used in the form of vibration, a cold drink with sugar ( such as orange juice or soda ), or palpation stimulation.
The NST comes with the highest false positive rates of all of the tests, which is why it has become a controversial test amongst some groups.
Studies have been done that conclude anywhere from a 50%-75% false positive rate on average, sometimes reaching as high as 80-90%. False positives will lead to more testing, more stress, and possibly unnecessary intervention in the pregnancy."
And in regards to the above comment, the article cited with the non-stress test in the title is dated from 1979: "Evertson LR, Gauuthier RJ, Schifrin BS, et al., Antepartum fetal heart rate testing. I. Evolution of the non-stress test. Am J Obstet Gynecol 1979;133:29-33"
Though I did not read this article, I have to wonder if the information contained therein is up to date regarding the "false positive" information?
Thanks for the link and info! Always good to have more articles to add to my "overdue" bookmark since that's always a topic here - especially those being bullied into early inductions. I really appreciate your counter-argument as it clearly gives reasonable evidence in support of your questioning of the original statements of the article quoted. You always have very concise and informative information and I always add the links you give to my growing library of study material!
regime rapide
Great post...however, I notice when you read through the references, not one is from the past five years. The most recent was from 2000. I would question the accuracy of any information offered regarding midwifery and obstetrics research that is not from the past five years. The author points out herself, that providers may be using studies to dictate their practice, which are outdated and since found to be inaccurate. One should be careful that the 'new' studies supporting the author's statement are not also outdated. True statiticians would laugh at research done in obstetrics and midwifery.
I want to be very clear - I am not arguing for inductions at 40 weeks or 41 either. Just want women to understand that when they do research, most 'old' obstetrical research is not accurate. You can look back at William's Obstetrics from back in the 60's, when forceps and twilight sleep were recommended as a best practice with better outcomes. You certainly won't find that in today's edition!
Wow, the responses are overwhelming! I'm glad that most have enjoyed the article. I put a lot of time and effort and heart into it.
To answer a few questions :
Michelle,
As a Midwife, I would say that yes, your cesarean likely could have been avoided just from what you told me. When an induction occurs when a baby and body aren't ready, the body does just what it's supposed to do : it protects the baby. It's not a malfunction of your body, but rather functions rather beautifully in what it's supposed to do. Unfortunately, in the hospital, that means a cesarean for failure to progress. :( But had your body and baby been allowed to work in its own timing, it's very unlikely that you would have had a cesarean at all. I'm so sorry that you were led down that path.
To address the dating of the research ... I agree, most of it would be considered "outdated". Unfortunately, there isn't much recent to show these things. Maybe because it's not considered important? I'm not sure. If anyone has seen updated research on NSTs and CEFM. As for the NSTs having "false positives", I meant that studies have shown that there is a decent rate of panic surrounding a seemingly non-reactive baby, when in fact everything was just fine. Anecdotally, before I had studied birth or became a Midwife, I had several NSTs with my son. The last of which showed him to be non-reactive, despite sugar, stimulation, and a repeat done a few hours after eating a full meal. He was just fine, but I nearly agreed to an induction. Thankfully, they were too full, and I agreed to a repeat NST 2 days later. And I really have to question WHY non stress tests are being done at 40/41 weeks, when we know that normal gestation is up until 42 completed weeks.
"When an induction occurs when a baby and body aren't ready, the body does just what it's supposed to do : it protects the baby. It's not a malfunction of your body, but rather functions rather beautifully in what it's supposed to do."
Whoa. Wow. WOW. I never thought of it that way before, but you are so right! In a way (a sad way) a failed induction in most cases is actually an affirmation of the wisdom of the mother's body. What a revelation! I may have to throw that up on my own blog, it's so brilliant.
To follow up, I did attmept a search on Regis University Library's nursing article database on NST and "false positives" after posting- I wanted to see if I could pull up some of the references listed here. It IS hard to come by recent and meaningful research regarding NST reliability as a predictor of outcomes.
All said and done, based purely on my own experience as an L&D nurse and what I have seen, elective inductions of labor are grossly "oversold" to women today. The idea that the body cannot be forced into what it is not ready to do is proved day after day on labor units as women subsequently "fail to progress" during an induced labor. The medical field compounds the problem by adding "failure to wait" on top of the pile of interventions heaped upon the pregnant woman seduced by the appeal of induction.
As a night shift RN, I have to say one of the upsides to 3rd shift is that induction and augmentation of labors in the middle of the night when the physican would rather be sleeping is much less prevalent. We are lucky and privileged to attend many more spontaneous and unmedicated labors because we do not have doctors pressuring us to "actively manage" labors in the dead of night. When I start to get weary of graveyards, I think of how much less enjoyable my job would be if I worked days and had countless inductions to manage in an arbitrary timeframe so that someone who gets paid a lot more than me can get home in time for supper.
Jill or anyone else, how does the 'the placenta is deteriorating and only meant to 'live' for 9 months' card play into this. Do you ahve more information about this?
As a side note, in response to some other comments about this, with my 4th and last child, I went to see a hospital attached cnm (no offense to anyone, just being specific as this was my first exposure to anything 'medical' as far as pregnancy and birth goes) because we couldn't afford our direct entry midwife at the time. Long story short: I also know when I conceive, this was my 6th pregnancy and I knew what I was talking about. Not only did she never write down in my chart when I told her I conceived (she based it on fundus height at around 12 weeks...), she also did not write down that I had felt movement ( I happened to see the chart), saying it was too early and that most women don't know when they conceive and that if they think they do, they are often simply wrong. She went on to insist on an ultrasound because she was convinced I was wrong (I think I was not big enough for 12 weeks while my history shows small babies considering my built and weight -180-200 with 6 lbs babies). Needless to say I was out of there asap. I was already on the way to unassisted birth, was just going to see her for prenatals, but unassisted pregnancy it was then too.
Blech, and then people wonder why we are so unhappy with it all.
Maria - I'm personally not sure about any studies with the placenta as far as "only meant to live for 9 mos" thing ... but I have to wonder : what about the moms who WON'T birth before 42 weeks? Anecdotally, I have a friend who probably will never deliver before 43 weeks. Her first was at 43 1/2, second was at 45. Her mother, grandmother, and maternal aunts all have roughly the same gestation length.
With proper nutrition, rarely do I see a placenta simply "deteriorate", and baby not be on the move for birth. I think it's all related to when baby is ready, in a normal, healthy pregnancy. As I said in this article ... I have attended the birth of a 36 week baby, where the placenta looked "older". Mom had all of her babies around 36 weeks. Just a few weeks after that, I attended the birth of a 43 week baby. He was covered ( and I mean COVERED ) in Vernix, and the placenta looked extremely healthy.
The problem with cookie cutter protocols, is that no 2 women are the same.
I'm so sorry for your experience with the CNM. It always blows me away when *any* provider doesn't hold any belief in women who actually know their body. :( I hope that you have peace with your plans, and go on to have a beautifully peaceful birth.