Intrauterine Growth Restriction- What Do We Really Know?

What might these scissors have in common with typical management for IUGR?

Disclaimer: I am not a medical professional. I encourage everyone to read, examine the evidence, use their own mind, examine what their intuition is telling them, and find a care provider that they can trust before making medical decisions for themselves or their babies. 


First of all, I think it's worthwhile to evaluate some medical and obstetrical practices that SEEMED to make sense when they were devised, but, in retrospect, and sometimes after several years or even decades of practice, have been thoroughly debunked as downright useless, or, even worse, harmful to numerous mothers and babies. There are many, so I'm just going to pick on one for a minute.

How about routine episiotomy? An episiotomy is when the doctor or midwife, during the second stage of labor (pushing), makes a small cut to the perineum to make more space for the baby. As recently as 1979, episiotomies were performed on 62.5% of women in the US, and 80% of women having their first baby. It's not too difficult to see the "logic" in helping make the vaginal opening a little bit bigger, faster. Proponents felt that it reduced trauma to the baby, helped the baby to be born faster, and reduced the chance of severe maternal tearing. 

But does it? Surely, a surgical procedure which scarred millions of women must have SOME backing in "science"? Actually...not really. Until 1921 episiotomies were almost always only performed on women with severe health issues to speed up the birth of their babies. Then an OB wrote an opinion piece on how wonderful it was for women to have episiotomies cut and their babies pulled out with forceps....ALL women. He thought it was easier to stitch up and made birth less stressful for babies. By 1938, a survey of obstetricians found that most supported the routine cutting of women's bodies during labor, and that it was beneficial and needed "no defense". Decades later, it's now fairly common knowledge among midwives and obstetricians that episiotomy almost never "helps" the baby unless there is truly an emergency situation where the baby must be born quickly (often with vacuum or forceps). Otherwise, the mother often tears worse during an episiotomy and needs MORE stitches or a more extensive repair than if she had torn naturally. (Here is an extensive review of the evidence against episiotomy). In my area, the episiotomy rate, even with obstetricians, is between 5 and 10%, a far cry from just a few decades ago. 

But it took close to 80 years for episiotomy to start to fall out of favor, despite the initial lack of evidence, and then subsequent evidence against it. Directed "purple" pushing, supine pushing, continuous fetal monitoring, denying women food and drink during labor....these are just a few more interventions that are common to birth in the developed world that seemed like a good idea, yet the evidence has shown that these practices may be necessary for a small minority of women, but are generally not helpful and often cause significant of collateral damage to a majority of mothers.

That was a really long-winded way of saying, 'Hey, let's take a step back and think critically about ALL interventions...even if they SEEM like they might be based on "common sense". I believe that the management of intrauterine growth restriction (IUGR) is a perfect example of this, and for whatever reason, it seems to be coming up more and more lately. 

As a doula I love to help women to do their own research. However, I often feel frustrated when discussing IUGR with clients or even other doulas, because I hear this SO often:

"If the baby isn't growing, it's better off out than in!" There almost is the feeling that it's okay to question all of these other interventions, but NOT a diagnosis of IUGR, because surely the doctor must know what is best at that point.

Now....I understand the thought process behind that, and indeed, often women who are carrying babies who are suspected to have IUGR are either induced early (some even as early as 36-37 weeks), or their babies are delivered by cesarean. It's truly BELIEVED that these babies are in imminent danger and will be better off in the capable hands of the medical staff. BUT....is that evidence-based? How is IUGR diagnosed? What babies are truly at risk? Does early induction improve outcomes, or is watchful waiting a reasonable choice? What are risk factors for a false diagnosis of a growth-restricted baby?

Let me also be clear that this article is mainly addressing "late onset IUGR", which is usually diagnosed in a third-trimester ultrasound right around or after 36 weeks gestation. Early onset IUGR has a much higher mortality rate and babies who are diagnosed before 28-30 weeks, using the same criteria that will be discussed, have a much higher risk of stillbirth. (I've seen numbers from 2.5% to 14% in various studies, and the majority are born preterm). Most researchers note that they wish there was more information available on how to help these babies, but unfortunately the data is not conclusive.

How is IUGR traditionally diagnosed? 

Approximately 5-8% of women will have a baby diagnosed with IUGR, but this percentage is higher and lower in distinct populations. Some fetal abnormalities, like congenital heart defects, trisomy genetic disorders, multiple gestation (twins or more) pregnancies, or pregnancy complications such as pre-eclampsia and diabetes increase the risk of growth restriction for the baby. Smoking may also be a risk factor. The classical diagnosis involves a fundal height (for the mother) behind by 4cm, an ultrasound weight estimation below the 10th percentile, and abdominal circumference that falls below the 2.5th percentile. However, these criteria have been recently questioned. The tricky part is identifying babies who are "constitutionally small" from those that are truly growth restricted.  

This study examined babies who were suspected to be SGA (small for gestational age) and compared outcomes to those that were not suspected, but had weight below the 10th percentile. Babies in the suspected group were born much sooner due to elective induction or cesarean, and had lower birthweight than those in the non-suspected group. Admissions to the NICU past 7 days were about the same in both groups. So basically, if care providers thought that the babies weren't growing, they delivered them sooner, performed more surgery, but babies that were left alone gained more weight and didn't die at a higher rate. Which group would you rather be in if you were the baby? This, and other research, calls into question the wisdom of automatically delivering babies who are suspected to be small just because it seems like they would be better off "outside".

What have recent studies suggested are risk factors for true IUGR and adverse outcomes, including death?

Weight below the 3rd percentile (NOT 10th)
Poor umbilical artery results
Amniotic fluid volume (via ultrasound estimation) less than 5cm. 

Combinations of these factors seem to be most concerning. In one study of over 1,000 babies, all of the deaths (8) occurred in babies who had weight below the 3rd percentile. Abnormal umbilical artery doppler was also strongly associated with admission to the NICU and other adverse outcomes, likely because this can be a symptom of poor placental function.

The authors of this study note, "Our data call into question the current definitions of IUGR used. Future studies may address whether using stricter IUGR cutoffs comparing various definitions and management strategies has implications on resource allocation and pregnancy outcome." 

What is the evidence for management of a pregnancy where baby is suspected to have IUGR after 36 weeks?

Actual management is quite varied, and often doesn't rely on the most recent evidence. Several surveys of physicians have found wide variation in the diagnosis and management of IUGR pregnancies. In this survey, the ONLY question that all of the obstetricians agreed on was that none of them informed mothers of the reoccurrence rate of IUGR in subsequent pregnancies! 

One of the largest studies yet published in 2010 compared 650 women with a pregnancy suspected to be complicated by IUGR at 36 weeks or above and randomly assigned them to induction or watchful waiting, with increased surveillance of their babies. The results were surprising! The induction group was delivered an average of 10 days earlier and, not surprisingly, these babies averaged about 4.6 ounces lighter than babies in the watchful waiting group. No babies were stillborn in either group, and the cesarean rate was about the same (14 and 13.7%, respectively). The authors summarized their findings this way-

"In women with suspected intrauterine growth restriction at term, we found no important differences in adverse outcomes between induction of labour and expectant monitoring. Patients who are keen on non-intervention can safely choose expectant management with intensive maternal and fetal monitoring..."


Watchful waiting generally includes weekly or bi-weekly non-stress tests or bio-physical profiles for the baby. Since induction increases risks of fetal distress and cesarean, particularly in first-time mothers, watchful waiting seems to be no more risky for babies than induction. Another analysis of this study found that NICU admissions were lower after 38 weeks, and concluded that delaying induction until at least that point was likely to decrease NICU stays and the associated risks to babies.


Is elective cesarean recommended for suspected IUGR at term?

No, unless there is clear evidence of fetal distress in the form of abnormal doppler artery flow and low amniotic fluid. In this study, elective cesarean birth significantly affected morbidity (injury or adverse outcomes) for mothers, but did not significantly improve outcomes for babies. "After 36 weeks of gestation, IUGR due to suspected placental insufficiency can be managed equally effectively by early delivery or delayed delivery with increased fetal surveillance." (Practice bulletin from SCOG). Elective cesarean delivery is not recommended by ACOG or SCOG. 

What are risk factors for a false diagnosis of IUGR?

Researchers examined the records of women who had been suspected of carrying a baby with IUGR, but the diagnosis was not confirmed at birth. They found a few common denominators. In the majority (over 60%), the fundal height was normal. Nearly 30% had been subjected to 2-6 ultrasounds before 32 weeks of pregnancy. Also importantly, over 50% of babies had at least one ultrasound measurement over the 10th percentile. They summed up their findings in this way: "The false diagnosis of IUGR involves high hospital costs and higher demand for specialists. The symphysis-fundal height measurement must be valued, and the diagnosis of IUGR must be confirmed with ultrasonography in the last weeks of pregnancy before any obstetric management is taken."


I would add that the cost is not only to the hospital and care providers, but also to parents and babies. Instead of the last few weeks being a time to treasure and keep as a safe space for the baby, parents with babies who are given a diagnosis of IUGR, false or not, often spend those last weeks with their baby stressed, anxious, and worried. They may also have to bear a heavier financial burden by the end of the process. Parents and babies deserve evidence-based care, NOT fear-based. 


Here is what I would wish to convey, in a nutshell.


Medical and obstetric history is filled with practices that seemed helpful, but actually are either not supported by evidence or have even been proven to be downright dangerous. 

It's difficult to identify before birth babies that are simply small versus growth-restricted. Babies who are small for gestational age do not have the increased risk of stillbirth, NICU admissions, and breathing difficulties that IUGR babies do.

The most current evidence suggests that diagnosis of IUGR is most accurate when taking into consideration multiple parameters: Estimated fetal weight below 3rd percentile, abnormal umbilical artery doppler, and low amniotic fluid levels. Fundal height may also be a consideration. 

Current management of pregnancies suspected to be complicated by IUGR is extremely varied and often fear-based, yet recent evidence suggests that in the majority of cases after 36 weeks, watchful waiting is just as reasonable as induction, and may result in babies who weigh more at birth. 

Parents deserve to be partners in evidence-based care, and to be informed of all risks. Inductions and cesareans come with their own set of potential complications, and these need to be weighed with the risks of early delivery of the baby. It's also reasonable to ask for a second opinion! 




Have you ever had a baby diagnosed with IUGR before or after birth? What options were presented to you? I'd love to hear from you!