Natural Childbirth IIa: Is Ultrasound Necessary & Effective in Pregnancy? | Chris Kresser
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Natural Childbirth IIa: Is Ultrasound Necessary & Effective in Pregnancy?

by Chris Kresser

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“The routine use of ultrasound in pregnancy is the biggest uncontrolled experiment in history.”
Beverly Beech, birth activist

In the first article in this series on natural childbirth, I presented evidence that – contrary to popular belief – hospital birth is no safer than home birth.

I’d like to begin this next article by telling you what it is not. It is not a blanket condemnation of ultrasound, nor is it a judgment of women who choose routine ultrasound during their pregnancy. It is not an argument against using ultrasound to investigate suspected problems, or to detect potential abnormalities, provided the woman is adequately informed.

The purpose of this article is to clarify the issues surrounding ultrasound’s use in clinical practice, to critically examine the clinical benefit of routine prenatal ultrasound, and to raise awareness of the potential risks associated with repeated ultrasound scans.

This was going to be a very long article, so I decided to split it into two parts. In part A I will discuss the use of ultrasound in clinical practice and examine whether it improves birth outcomes. In part B, I will review studies on the safety of ultrasound as it is used today, and make recommendations for expecting mothers.

History of ultrasound and use in clinical practice

Ultrasound was originally developed in WWII to detect enemy submarines. After the war in 1955, a surgeon in Glasgow named Ian Donald began to experiment with it for medical uses. Using beefsteaks as “control” subjects, he scanned the abdominal tumors he had removed from his patients and found that different tissues gave different patterns of sound wave echo. He quickly realized the potential of ultrasound for examining a growing baby in utero.

Initially, ultrasound was used only to investigate possible problems. For example, if there was bleeding in early pregnancy, it would be used to determine whether miscarriage was inevitable. Later in pregnancy, if breech or twins were suspected, ultrasound would be used to confirm that suspicion. In these cases, ultrasound can be very useful for a woman and her caregivers.

However, over the years ultrasound has come to be used as routine scan at 18-20 weeks for all women. This is referred to as “routine prenatal ultrasound”, or RPU for short. It involves scanning all pregnant women – whether a problem is suspected or not – in the hope of improving birth outcomes.

As often happens in medicine, techniques which may be of value to a small percentage of people slowly become adopted for routine use without prior study of benefits. A perfect example of this is the alarmingly common prescription of statin drugs for women, children and men without pre-existing heart disease, in spite of the fact that they’ve only been shown to be effective for a small segment of the population: middle-aged men with pre-existing heart disease.

The problem with this approach, of course, is that when we perform a procedure or administer a treatment to a segment of the population without properly testing it beforehand, we are essentially conducting an uncontrolled scientific experiment on that population – often without their understanding and consent.

And in this case, we are performing that uncontrolled experiment on two of the most vulnerable populations: pregnant women and babies in the womb.

Some physicians and researchers have been questioning the wisdom of performing such an experiment for decades. In 1987, UK radiologist H.B. Meire remarked:

The casual observer might be forgiven for wondering why the medical profession is now involved in the wholesale examination of pregnant patients with machines emanating vastly different powers of energy which is not proven to be harmless to obtain information which is not proven to be of any clinical value by operators who are not certified as competent to perform the operations.

More recently, in 2010, the prestigious Cochrane Collaboration reviewed the available evidence on routine prenatal ultrasound (RPU) and concluded:

Existing evidence does not provide conclusive evidence that the use of routine umbilical artery Doppler ultrasound, or combination of umbilical and uterine artery Doppler ultrasound in low-risk or unselected populations benefits either mother or baby.

Despite the lack of evidence supporting RPU’s use in clinical practice, ultrasound is almost universally seen as a safe and effective procedure, and scans have become a “rite of passage” (in the words of Sarah Buckley) for pregnant women in most developed countries.

In the U.S., an estimated 65 to 70 percent of pregnant women have a formal scan in a diagnostic clinic, and many more women are scanned by their OB/GYN as part of their pregnancy visit.

Is ultrasound as effective and safe as we’ve been led to believe?

In order to answer that question, we have to distinguish between different uses of ultrasound. As I said earlier, ultrasound scanning can be a useful diagnostic tool when abnormalities are suspected. I have no argument with using it in this manner. The question I’d like to investigate here is whether routine prenatal ultrasound – when no abnormalities are suspected – is necessary and effective.

RPU is used today for several reasons:

  1. To predict the birth due date
  2. To determine the sex of the baby
  3. To detect potential abnormalities
  4. To identify placenta previa (low lying placenta)
  5. To assess specific markers, such as the length of woman’s cervix and the amount of amniotic fluid at the end of pregnancy

It’s almost as if all pregnancies are immediately suspected to be abnormal until proven otherwise. In the words of TM Marteau 1:

Before the development of prenatal testing for fetal abnormality the fetus was assumed to be healthy, unless there was evidence to the contrary. The presence of prenatal testing and monitoring shifts the balance towards having to prove the health or normality of a fetus.

The important question is: is RPU necessary and effective for these uses? Does it improve specific birth outcomes like perinatal mortality or morbidity?

Routine prenatal ultrasound is not recommended by researchers and major organizations

In general, RPU is accurate for predicting birth date when scans are performed in the early stages of pregnancy. The estimated due date (EDD) calculated by a scan at 7-8 weeks will be accurate to plus or minus 3-4 days.

However, calculations of EDD based on a woman’s menstrual cycle can be just as accurate.

What about detecting abnormalities? Studies show that RPU detects between 35-80% of the 1 in 50 babies that have significant abnormalities at birth. The larger centers with better trained sonographers have rates toward the higher end of the scale, but even major centers miss 40% of abnormalities.

That’s because many abnormalities are difficult or impossible to detect with RPU. Heart and kidney problems are unlikely to be picked up, as are some markers for Down syndrome. Cerebral palsy, autism, and other markers of intellectual disability are impossible to detect.

Then there’s the small but significant chance that an abnormal finding may be a false positive. A UK survey showed that for 1 in 200 babies aborted for supposed major abnormalities, the diagnosis on post-mortem was less severe than predicted by ultrasound, and the termination was probably unjustified. In the same survey, 2.4 percent of babies diagnosed with major malformations – but not aborted – had conditions that were significantly over- or underdiagnosed.

Two other studies have shown false positive results in roughly 10% of babies diagnosed with structural abnormalities. And in some cases, the abnormalities spontaneously resolve without intervention.

In addition to false positives, there are also cases that are difficult to interpret, and the outcome for the baby is unknown. This uncertainty can cause considerable stress and anxiety for the mother, which in turn adversely affects the developing baby. In one study involving women at higher risk, a full 10 percent of scans were uncertain. And in that same study, mothers with uncertain diagnoses were still anxious three months after the birth of their baby.

Ultrasound scanning for placenta previa is mostly accurate, but almost all women who test positive for it on a scan will be unnecessarily worried. Studies show that the placenta will move up and not cause problems during birth for 80 to 100 percent of women, and that detection of placenta previa by RPU is not safer than detection during labor.

All of this might explain why organizations like the American College of Obstetricians and Gynecologists recommend scans only for specific reasons, including uncertain due dates and fetal assessment, and advises that routine prenatal scans are cost-effective only when done by ultrasound technicians working in high-level centers.

In Canada, practice guidelines recommend only a single midpregnancy scan and stress that information on risks and benefits must be provided and informed consent obtained.

Routine prenatal ultrasound does not improve birth outcomes

Studies on RPU over the years have consistently shown that it does not improve birth outcomes as measured by clinical endpoints such as perinatal mortality and morbidity.

A 1993 meta-analysis of all randomized trials prior to that date covering 16,000 births showed no improvement in the condition of babies measured by APGAR score when ultrasound was used compared to those who did not have it. There was a slight reduction in perinatal mortality in this study. However, this happened because these babies were aborted during pregnancy – not because their lives were saved. There was no increase in the number of live, healthy births from RPU.

The authors of this study concluded:

Routine ultrasound scanning does not improve the outcome of pregnancy in terms of an increased number of live births or of reduced perinatal morbidity. Routine ultrasound scanning may be effective and useful as a screening for malformation. Its use for this purpose, however, should be made explicit and take into account the risk of false positive diagnosis in addition to ethical issues.

In another 1993 review covering 15,530 births the authors found “no significant differences in maternal outcomes”. The rates of induced abortion, amniocentesis, tests of fetal well-being, external version, induction, and cesarean section and the distribution of total hospital days were similar in the two groups. They concluded:

Screening ultrasonography resulted in no clinically significant benefit.

In the same year (1993), the World Health Organization (WHO) issued a letter reviewing the studies performed on routine ultrasound to date and concluded 2:

It is fair to say that at the moment the best research shows no benefit from routine ultrasound scanning and the real possibility of serious risk. …we urge you to reconsider all present policy with regard to routine ultrasound scanning during pregnancy, based on these important scientific papers.

Articles in this series:

  1. Beech, BL. Ultrasound unsound? Association for Improvements in the Maternity Services. 1996
  2. Beech, BL. Ultrasound unsound? Association for Improvements in the Maternity Services. 1996.

53 Comments

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  1. Transvaginal ultrasound with color Doppler is the ONLY way to detect VASA PREVIA. 95% of undiagnosed babies die. 98% of diagnosed babies survive (with proper management).

  2. This absolutely infuriates me.
    As someone who was just recently diagnosed with vasa previa, an extremely rare (1 in 3000) placenta related issue that occurs during pregnancy and can ONLY be diagnosed with an ultrasound, articles like this make me livid.
    If my condition went undiagnosed and most of them do, the risk of fetal death (baby dying during birth) due to a burst blood vessel is 95%!
    Instead, I’m getting expert care and now my little one has an almost 100% chance of survival. I’m truly grateful to my doctors, the smart ultrasounds tech that recommended a vaginal sonogram and modern medicine.
    Please, everyone, do not miss any of your scheduled ultrasounds. Make sure you DEMAND a vaginal ultrasound at 20 weeks, as often times vasa previa is totally missed without one.
    If it can happen to me, it can happen to you.

  3. Hi Chris
    I am expecting twins at 16 weeks. I originally didn’t want any scans because of the unknown risks but I did have one to find out my due date..only to discover I have twins! Now there is more medical pressure than ever. I want to know if the 20 week scan is any more useful or necessary for twins than with singletons. I am willing to try and have as natural a pregnancy as I possibly can but I wouldn’t want at any point to put my twins at risk just because of my beliefs. Thanks

    • During the past two years research, I compiled a new bibliography of ultrasound exposure studies. These are human studies, high-tech laboratory studies, that observed the results of ultrasound exposure to a total of 2,700 women-fetus pairs. These are approximately 50 studies over a 23 year period.

      Ultrasound appears to be much higher risk than commonly publicized. The risk/benefit should be reevaluated in light of these studies. See http://harvoa.org/chs/pr

    • Any ulyrasound you will have in future will effect your unborn babies. Utrasound heats up the tissue and cause damage. There are over 50 studies done in China on aborted foetuses in all stages of ptegnancy and all of them proved dangers of ultrasound. There is a book on this topic written by Jim West and he compiled the main data and it’s shocking this is not in every sonographers library. I am pregnant 29 weeks and didn’t have any ultrasounds. I am a healthy female and my baby is kicking strong i eat right don’t inject myself with harmful vaccines and i believe my baby is healthy. Babies were not exposed to ultrasounds for thousands of years and we’re born fine so i am going to take my chances. I bet i will be just fine.

  4. Ultrasound is a necessary element to watch out the developments in baby and the other complications. It is also very effective for women who want to become pregnant, but do not know about their previous tubal procedure. It helps to find the right surgery type for reversal.

  5. I’m scheduled for an 8 week ultrasound this Wed, Dec 5th, 2014, because we’re unsure how far along I am. Is this a legit reason for an ultrasound or should I opt to skip it?

    • I have irregular cycles and we had an ultrasound that was supposed to be at 12 weeks but turned out to be just at 6 wks! That was because their dating based on last cycle was a month and a halve off.
      I don’t know if there is a non-invasive way like measuring the uterus size by hand etc. (I saw that done on ‘Call the Midwife’ 🙂 because after my ultrasound I had very severe cramping for a couple hours that I haven’t had before or since…( I had the probe thing and two ultrasounds on top of that one.) But you also have to consider what the policy is on overdue/early babies is in the place your giving birth since you don’t unnecessary interventions just because your due date was not accurate.

  6. I am faced with a serious problem. i did an ultrasound and was told by the doctor that he did not see anything. but yet and still my stomach is growing and according to my nurse who examined me just last week i am 31 weeks and that everything is fine. Can you please help cause i am confused and worried.

  7. My oldest daughter is approximately 10 weeks pregnant and has already had three ultrasounds. Two were performed at the college where she is in school to become a dental assistant. At the school she has had two of the three sounds performed for fun. The other sound was performed at her first prenatal doctor appt which I attended with her. The PA advised my daughter to limit anymore ultrasounds and her face showed a face of disapproval that my daughter had already had two sounds. My daughter knows I do not approve of her getting so many sounds done and she claims it’s perfectly safe because her friend who is a ultrasound tech states sounds are perfectly fine. I want to know the long term effects on children who have had so many sounds when in the womb

    • As a professor and director of an ultrasound program, I say shame on your daughter’s friend for stating this is perfectly fine! It is NOT! I teach my students, and our pregnant volunteers, that there are no KNOWN risks but that we have guidelines set forth by our governing bodies and our Code of Ethics. Certainly concentrating that much sound on such a small area (a 10 week fetus is obviously MUCH smaller than a 39 week fetus) is not advisable multiple times unless there are clinical symptoms indicating possible problems. I don’t know of any legitimate, reputable sonographers in my area who would take this lackadaisical approach to this topic. While I do not agree with the author’s view that routine screenings really aren’t necessary, I do believe we have the responsibility to be cognizant of the role we play in healthcare. Further, I refuse to participate in any ultrasound examinations ONLY for the sake of entertainment or revealing a baby’s gender!

  8. How does a woman know if she has a high risk pregnancy ? Does carrying twins warrant a high risk pregnancy treatment and again without ultrasound scan it could not be known whether woman is carrying twins or not for sure? Am I right ?

    I am not yet pregnant but trying to be, before reading this article I had never ever given any thought to ultrasound scan sand thought of it as a normal necessary procedure for all pregnant woman.
    Thanks Chris, you shared quite useful information, which would allow women to make an informed choice.

    • Yes, carrying twins is considered a high risk pregnancy. Age can be high risk, whether below or above certain ages. Family history can be high risk. I suggest talking to your gynecologist about all the categories that could constitute high risk and you will probably be surprised at how many “regular” women fall into! I teach ultrasound and I do not agree with the author’s viewpoint on the necessity of a routine screening. I do not believe most of us look at it as assuming things are wrong until proven otherwise. I believe in preventative medicine, just like immunizations. An ultrasound at around 20 weeks gestation can confirm that things are progressing as expected and desired. It can also reveal if there are any abnormalities that might prevent a safe vaginal delivery BEFORE the mother spends hours in unnecessary labor. Further, it can reveal abnormalities that warrant a plan of delivery in a hospital with a NICU (neonatal ICU) for immediate attention. Yes, while few babies are born with diaphragmatic hernias, or omphaloceles, or gastroschisis, or a host of other issues, there are still quite a few who are and whose lives have been saved to go on and lead normal, productive lives because of prenatal ultrasound. Without the prenatal ultrasound, these would not have been discovered, planned for appropriately, and turned out in a positive outcome.

      • I think the main point behind the label ‘high risk’ is the mothers health. If there is bleeding, high-blood pressure or diabetes diagnosed you can be considered high-risk. This is for your doctor to diagnose. It’s not as simple as what age you are, it’s primarily based on the mothers health and is a rather qualitative judgement in many cases.

      • I come from a family of doctors and BS nurses. many of my family are either or. i do not agree with ultra sound nor vaccines. studies have shown they are the cause of many problems as autism. they have mercury, aluminum and many other substances in vaccine. I fine it strange that only the man race has to depend on science that says it is ok to use these machines which are not proven to be safe. take for example monkeys do they have doctors to deliver their baby? elephants, horses.all were designed by the creator and yes there is things that happen in this world of sin, but Natural is the creators way!
        Put your trust in the divine not man! there is no complication unless you are having complication. My last child and i have had 4 and am 64 was totally natural and no ultrasound and didn’t know his sex until birth and i said it was a boy and it was! trust Yahuah not man’s devices.
        fact the CDC gave Africans the yellow fever shot and 5 years later near 90% that received the shots had aids and they admitted they tainted the vaccine! do your research before trusting man!

  9. Hi Chris! I am due in May and at my 19 week scan I was just anxious to find out where my placenta was because I was planning a hbac. I am so disappointed to and distraught to find out I do indeed have a partial previa. The high risk ob mentioned possible accretia because I my prior csections. They are going to closely monitor me with extra scans :/. Now I just read your article and feel a little better that the previa may resolve itself. A little worse because this scan was more in depth of any I ever had and they want to do more :(. There were colors on the screen so I assume it was MRI like ? To be able to look at the blood vessels (they didn’t do this with my first hbac and I had a 10 lb baby quickly delivered without tearing with “scant” bleeding, but now that I am 42…so in high risk..). And it was at least an hour :/. They want to recheck the previa in a month around 24 weeks. I am wondering if I should just politely refuse until closer to my due date. I of course came home an googled partial previa and accretia and was so upset and crying for days.. This has caused me much anxiety indeed!!!!!! Any thoughts are welcome 🙂
    Monique

  10. Hello there. I am one of many women who have gone through a missed miscarriage. As you know this normally occurs in the post-7 week early pregnancy mark where the body believes it’s still pregnant but the baby no longer develops or has a heartbeat. There are no signs such as bleeding, cramps etc to really indicate it’s happened. My first prenatal visit was at 8 weeks. The doctor did a very quick preliminary u/s which determined a hb of 160 but the measurement sounded behind to me knowing my ovulation day– nevertheless i didn’t really speak up. Then he said, well you’ll come for a more official u/s with the technician next week and we’ll do a more thorough measurement but this was just to assure you your baby is alive and fine. Sure enough I arrived a week later to an ultrasound where the baby no longer had a heartbeat. There was real emotional shock and anxiety and having a wand up inside me while I was being told things are over was a bit cold and devastating. I am still months later a bit traumatized from that. So what happened then was as many women are told, you can either try to wait for a few weeks for the baby to naturally miscarry, which just sounds foreboding to have to wait weeks for a miscarriage, or you can get a d&c procedure and move on with your life. I opted for the latter, feeling completely adverse to emotionally handling weeks of waiting. By the way, you are mostly told as well that if you opt for natural miscarriage you can often end up having to have a d&c anyway to fully clear the area. There were no good answers because it overall feels awful. I am not alone. There are millions of women who go through that every day. It’s probably stupid to say, but I would rather have had alarm bells like blood or something to indicate something is wrong rather than an u/s tell me. It left me feeling powerless. So now, I’m pregnant again (still trying for my first) and next week is the same time u/s that detected my sad fate last time. I don’t want to go through it. I will not be looking at the screen and not be looking at the technician. I dread it. I will dread it every time i may have to go in. The whole process was pretty expensive. Even with good insurance, the whole thing ended up costing me over a thousand dollars at the end of the day for all the medical bills just for one miscarriage. I don’t really know. If the stupid machine tells us something’s wrong, I suppose that helps in some way, but the statistics are that something can go wrong as much as 40-50% of the time, so it makes sense. I just hate the whole process. I wish I could be part of a more ‘ignorant’ time where people didn’t worry about this all the time.

    • I agree. My first pregnancy had complications not picke up at the first 12 week scan but at the 20 week scan. This was then followed by lots of other scans and a grave outlook. I knew my son would be ok and he is – although I think very mildly in the spectrum. My second pregnancy proved the same. Early scan fine, abnormalities at second scan. I ended up miscarrying followed by a D&C but I actually feel I was pushed into that. I would have liked to have miscarried naturally. I’m now pregnant again and my partner supports my decision not to tell the GP yet as with my past history they will push me into routine examinations. Especially since my last miscarriage also resulted in PID and a hospital stay. Got pregnant first try despite being wrongly told years ago that I have pcos. Another US diagnosis that resolved itself. I’ll have one scan mid pregnancy if I feel up to it but this time around I want to have control over my body and my babies and everyone else can back off! If this one makes it we will be over the moon. I think it will. If not then so be it. We will try again. Regulation is needed!

    • My first pregnancy was somewhat similar to yours…they did an ultrasound at 10 weeks and the baby’s heart wasn’t beating so they just figured it was because i wasn’t as far along as they had thought but I guess something was already wrong…and then at 11 weeks, 6 days I had a natural miscarriage. It was an emotional time for both me and my husband but God has blessed us with another child who is now 13 weeks and seems to be doing well&has a strong heartbeat…and this pregnancy around I’m going u/s free because I’d rather let nature take its course than stress about it like i did the first time around. I wish you all the best!

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