Natural childbirth IIa: is ultrasound necessary & effective in pregnancy?

July 11, 2011 in Babies & Kids, Fertility, Pregnancy & Childbirth | 20 comments


“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.

  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.

{ 20 comments… read them below or add one }

Jo July 12, 2011 at 9:23 am

Thanks for this analysis. As a mother from the pre-ultrasound generation, I could never understand why so many women were getting “routine” ultrasounds.


Sonja July 12, 2011 at 9:35 am

You forgot one reason for the ultrasound – to know the sex of the baby.


Rowan July 12, 2011 at 10:28 am

It’s listed as number two under reasons for RPU.


Mountain July 12, 2011 at 10:17 am

Huh…I never thought about ultrasound at all. It does seem imprudent to blast a fetus with sound waves, especially if it doesn’t do much medically.


Shaloma July 12, 2011 at 10:19 am

You are basically my hero… Thank you for being skeptical of mainstream medical interventions.


Martin July 12, 2011 at 11:23 am

I remember when my brother (a radiologist) and his wife (an MRI tech) were pregnant with their first child, they would go and duck into the ultrasound lab for “fun” and do an ultrasound on the baby. My nephew (now 12) must have been subjected to more ultrasonic waves before birth than most people are in their entire lives. Even at the time, I questioned him about how safe this was, and in typical MD fashion dismissed my concerns.

I come from four generations of Dr’s, and it never ceases to amaze me the blind faith the medical establishment puts in their own propaganda. I’ll be sure to forward this to him, it will give us something to discuss over dinner sometime soon. :-)


Abby July 12, 2011 at 12:05 pm

As a Certified Professional Midwife (CPM) I had a client quite a few years back who was a L&D nurse. She reported to me that she scanned her own baby (her 6th) almost every night when on duty, just for fun. Her baby was small for gestational age (SGA) or possibly intrauterine growth retarded (IUGR) though she never noticed this with her repeated scans. I, however, noted prenatally, that her baby felt much smaller than her other 5 children, using my hands to palpate her baby. The outcome was good, though the baby needed some resuscitation at the time of birth. I have always wondered if all those scans (hundreds of them!) actually CAUSED the problem.


Chris Kresser July 12, 2011 at 12:13 pm

Yes. Some evidence (which I’ll cover in the next article) suggests that multiple ultrasound exposures during pregnancy can increase risk of IUGR – which is ironic, because screening for IUGR is often one of the reasons given for performing ultrasound.


Bridgett July 12, 2011 at 12:09 pm

You put in to words what my gut was telling me eight years ago. Now, granted, I did end up having an ultrasound–at 36 weeks, when there was confusion of the position of the baby. Guess what? I was carrying twins! But honestly I’m glad I didn’t know sooner. Once I found out, the medical community started treating me like a sick person (high-risk pregnancy, yadda, yadda, yadda). I’m glad I only had to endure that nonsense for a few weeks, as opposed to several months had I had an ultrasound earlier.


Joann July 12, 2011 at 12:13 pm

This is the rose colored glasses approach to child birth. When my child was dead in-utero, I sure did want that ultrasound. Also, incompetent cervix is the number one leading cause of premature birth currently in this country. This is because of several reason one, it’s an autoimmune response caused by all the things you talk about and two, its undiagnosed and under reported and three, the treatment suggested by most main stream doctors is a wait and see approach, which ultimately ends is watching and seeing a premature birth.

My premature son’s MONTHLY hospital bill was $680,000, yes that’s monthly. Most premature babies live in the NICU for 3 to 4 months, that’s a whopping 2.72 million dollars per child. How much does an ultrasound cost again?

Maybe ultrasounds are used for the wrong reasons. Definitely they need to be used better for some cases, such as incompetent cervix. But to throw the baby out with the bath water seems ridiculous.


J July 12, 2011 at 1:32 pm

Thanks for the article, Chris. I got diagnosed with gestational diabetes. They hit me over the head with that horrid glucose tolerance test. They wanted to do another one, but I said hell no. “Here does this hurt when I hit you over the head with this giant hammer. Oh, OK, let’s try that again to see if it still hurts.” No way!

I said, let’s just treat me like I’m a diabetic and give me one of those meters. The monitoring of my glucose levels was just fine if I ate the right things. But, volunteering to be labeled as a diabetic dragged me into the monthly ultrasound protocol. At one of my sessions, I said to the Dr. that, my sugars have been just fine, do we have to continue with this Ultrasound monitoring? He got all angry and told me “babies die!” Well, that was a little heavy handed, doncha think? I continued with the ultrasonic monitoring.

How I wish I’d met you about 8 years ago, Chris.

My baby is just fine, but, I had the medicalized pregnancy of which you speak.


Victoria Morris-Ott July 12, 2011 at 3:03 pm

Whew! I refused an ultrasound in 1978 when pregnant with my second baby … I knew the due date exactly (husband only home a few days). I ended up with a low lying placenta, which should have been detected by other means. My gynaecologist told me “you put yourself and your baby at risk” — he was very God-like. We lived in Northern Alberta and he was routinely sending all pregnant women to Edmonton for the test (usually 3x a pregnancy). I did manage a natural birth, without medication I will add. Reading your article I was able to strike this particular ‘guilt’ item off my list. I am not sure what I would do, if given the same situation again. I suspect go with the ultrasound … but at the time they were very new and I felt unnecessary for the reasons given above.


Sarah Nickolet July 12, 2011 at 7:26 pm

I agree with Joann. My nephew was diagnosed with a serious Congenital Diaphragmatic Hernia on a routine ultrasound at 18 weeks. If they didn’t know that was the case then he would have been delivered in a very small hospital with no equipment that was necessary for him. It’s a very useful tool when we have specialized hospitals that can help save these precious bundles.


S, RDMS July 12, 2011 at 8:17 pm

The meta-analysis you site is from 1993. Ultrasound technology has grown in leaps and bounds since then.

I am a sonographer at a large hospital. I have myself discovered many major heart defects, in completely routine scans. I have discovered lung tumors,fetal teratomas, diaphragmatic hernias and many other defects in routine scans which lead to the baby being delivered with the proper team of physicians and surgeons in a hospital equipped to care for these cases.

I recently discovered a rather subtle heart defect which would have progressed a fatal outcome. The fetus had in utero surgery which saved its life. These are the sorts of things that are possible now. They were not possible in 1993. That baby is alive because of ultrasound and surgical technology.

Not all defects can be fixed in utero, of course, and yes – there are a lot of false positives which cause anxiety. But if it were my fetus with the huge CCAM or hypoplastic left heart? I’d want to know about it ahead of time to be prepared. I think everyone should have that option.


Chris Kresser July 12, 2011 at 8:34 pm

Yes, the technology has changed. Scanning intensities used today are much higher than in 1979-1981. In fact, outputs have been estimated to have increased 6 times between 1991-1995 alone. This makes it even more likely that routine prenatal ultrasound – as it is performed today – may cause harm.

A 2008 Cochrane meta-analysis found that routine ultrasound in 27,024 late pregnancies in “in low-risk or unselected populations does not confer benefit on mother or baby.”

A 2010 Cochrane meta-analysis of routine ultrasound in 37,505 early pregnancies found that “Routine scans do not seem to be associated with reductions in adverse outcomes for babies or in health service use by mothers and babies.”

Another 2010 Cochrane review of use of Doppler ultrasound in 14,815 normal pregnancies 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.”

So there we have 3 large, recent, well-designed meta-analyses covering over 78,000 women telling us clearly that routine ultrasound and Doppler during pregnancy does not improve outcomes (i.e. doesn’t benefit mother or baby) in low-risk populations.


Kayla August 4, 2011 at 6:36 pm

There are also women out there who don’t want to know, who will be told despite that, who will be badgered about have in-utero surgeries though they’d rather just let nature take its course. And when we decline we’ll be made to feel like murders, when in reality the medical profession doesn’t give a crap they are just looking for a paycheck. We are murders if we choose to decline pricey procedures and then were called responsible if we have an abortion because of defects or just because!


Janknitz July 14, 2011 at 3:02 pm

I had difficulty getting pregnant and there were a lot of issues including very early twin loss (in the early days of In Vitro Fertilization), so I was very COMFORTED with frequent ultrasounds to see that the baby was OK. I’m so grateful to have had them. Between US’s I was in terror that this baby, too, would die. Each US allowed me to relax and not worry so much because I could see for myself that she was fine.

In my last few months of pregnancy we moved to another state and my new OB did not have an in office US and did not believe in sending me out for one unless there was a “problem.” Well, there was–in my 6th or 7th month a previa had been noted, but because it was early and marginal they thought it would move away from the opening on its own. They didn’t tell me to restrict activity or anything. It was never checked again to see if it had resolved itself until a few days before my delivery date when I woke in a puddle of blood! It all came out OK, but there were several hours of terror until the hospital could get an ultrasonographer in to see what was going on. If I’d had some US follow-up, much of this could have been avoided.

I admit the outcome was the same (a perfect. healthy baby who just graduated from HS and is off to college!), but I still think the potential danger could have resulted in a very different outcome. If I’d had an US later in the pregnancy, we would have known the previa was still there and I would have been a lot more careful!


Bridgett July 14, 2011 at 4:51 pm

I think your history and circumstances would warrant ultrasounds. I think Chris’ article isn’t addressing such situations as yours.


Irina July 22, 2011 at 4:10 am

Dear Chris!
Thank you for the article! Unfortunately the main part of present Dr.s don’t want to understand that pregnancy is absolutely natural process in woman’s life and behave themselves with pregnant patients like they are ill.I live in Moldova and in my country and in post USSR countries all the OB/GY send women to RPU, in addition give a big amount of synthetic vitamins and at the end it happens that you take 10-19 different pills “only for baby” as doctors say, per one time. And when you ask doctors why do I need to do US or to take so much vitamins, they reply you “this is for baby” and that’s all!!! And I thought that we follow blindfold to all medicine innovations and don’t want to think that it can harm us as population.And even if now we can’t see visible harm, but it will pass 10-20-30 years and we will discover that US was the reason of many unpleasant things connected with health. We need to be more conscious before ourselves and our children!


Debbie July 23, 2011 at 10:06 am

Well I guess I was lucky with my doctor during my 1978 pregnancy, as she totally supported the idea that pregnancy is a perfectly natural process and “less is more” when it comes to treatment. I see one commenter about talking about being told she was putting her baby at risk by refusing an ultrasound in 1978. Heck, I don’t think I was even aware of ultrasounds! Certainly my OB never suggested I have one done, and so I never did. I didn’t even know they were around that long. Though my sister had one for her first son in 1981, but that was considered a “high risk” situation as her first pregnancy had nearly killed her, being ab ectopic pregnancy, so the next time around they wanted to make sure the fetus was positioned properly.

By the time her second and third kids came along it was starting to seem more routine.


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