Fetal growth retardation: what it is, how to intervene, what are the prospects for the future

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Catherine Le Nevez
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Iugr, what is it

A fetus that is not growing as it should. This, in short, is the definition of intrauterine growth retardation (or restriction), in acronym Iugr. Sometimes, the expression is also used as a synonym for a small fetus for gestational age - doctors refer to Sga (Small for Gestational Age) - but in reality these are two different conditions.

"A child small for gestational age is a child who presents a weight less than the XNUMXth percentile of reference with respect to the gestational age in which it comes into the world (for example a child born at 40 weeks of 2,4 kg). However, this low weight does not necessarily indicate a problem: it could be a constitutional fact"explains the professor , director of the obstetrics and gynecology department of the Buzzi Children's Hospital in our city, one of the leading experts in Del Paese di fetal growth retardation.

"A child with a stunted growth, on the other hand, is a little one when he is born has not reached its growth potential, that is, it has not grown as much as it could and should have if all its potential had found the right conditions to express itself. Typically, this happens because he hasn't received a adequate supply of nutrients".

In practice, what happens is that the fetus grows normally until a certain point in the pregnancy, but then its growth stops being regular and slows down significantly. "The technical definition requires there to be one decrease of at least 40 percentiles"says the gynecologist.


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  • Growth retardation, as can be seen
  • Iugr, the cause
  • Consequences of growth retardation
  • Possible remedies
  • Iugr, prevention
  • The perspectives of research

As we can see, there is a growth retardation

Usually it is with theechography which turns out if there is something wrong with the growth of the fetus. "The ultrasound scans done during pregnancy, whether they are routine or any extra ultrasounds planned for specific risk factors - allow us to check, among other things, how the fetus is growing," she says. "They are the equivalent of the measurements (weight and height) that the pediatrician takes in the first months and years of the child's life, always to check the progress of his growth".

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Iugr, the cause

"Only in 10-20% of cases it is possible to clearly identify a cause of the growth retardation, which can be of maternal, placental or fetal origin" explains .

For example, women who have autoimmune diseases, chronic or pregnancy-associated high blood pressure, diabetes, hemoglobinopathies and thrombophilias, severe malnutrition are more at risk. As for the clearly placental causes, they can be traced back to malformations of the placenta itself (or of the umbilical cord), or to one of its abnormal implant as in the case of placenta previa. Finally, among the fetal causes, there may be chromosomal anomalies and syndromes, such as Turner's or Down's syndrome. And some too infections they may be associated with growth retardation.

"More often, however, growth restriction occurs in pregnancies in which there are no known risk factors," explains the gynecologist. In other words: the mother has no pre-existing problems, the placenta looks normal, and the fetus has no chromosomal abnormalities. What happens, then, in these cases?

"We are talking about a generic placental insufficiency"he declares." What is known is that in these pregnancies the placenta has not formed adequately in the first few weeks, when theinvasion of the uterine wall by the trophoblast, the precursor of the placenta itself. "In practice, a correct contact is not formed between the cells of the placenta, which remain separated by free spaces: this constitutes an obstacle to the growth of the placenta itself and to adequate circulation. consequence oxygen and nutrients they do not reach how much and how they should the fetus, which obviously goes into suffering.

That something went wrong in the formation of the placenta can be seen a posteriori, once the birth has taken place, because the relationship between the weight of the fetus and that of the placenta is altered compared to the expected one (the placenta is smaller than how much it should). "But it can also be seen during pregnancy - she says - through the Doppler velocimetry of the uterine arteries". It is an instrumental examination that allows to evaluate the circulation and therefore the placental functioning.

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Consequences of growth retardation

The consequences of a growth retardation on the development and survival of the fetus depend on the severity of the delay itself and in particular on how early it occurs: one thing is whether the fetus stops growing adequately at 34 or 35 weeks, another if she stops doing it at 26 or 28. In the most serious cases there is a risk of stillbirth and premature birth, with all the possible consequences for this event.

Furthermore, more and more studies confirm the link between growth retardation during fetal life and increased risk of certain diseases during adult life. These include hypertension and metabolic syndrome, obesity, kidney disorders, psychiatric disorders such as schizophrenia. As always in these cases, it does not mean that all children who have suffered from Iugr will be affected, but simply that they will be more predisposed than those who have not suffered. This is why it will be necessary to pay more attention to other aspects of the lifestyle that could influence the risk.

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Possible remedies

Unfortunately, there is currently not much that can be done when intrauterine growth restriction is encountered. I'm not here therapies or interventions that can help the placenta to resume proper functioning, giving a boost to the growth of the baby.

"If the mother also has problems - very often fetal growth retardation is accompanied by the risk of maternal preeclampsia - the woman is given therapy to try to control the situation, but the only thing that can be done is I realize that the stay in the uterus of the baby carries more risks than benefits give birth".

In these cases, therefore, a early delivery (often with cesarean), preceded by the administration of corticosteroid medications which favor the pulmonary maturation of the baby.

To determine when the appropriate time for childbirth is based on the indications that come from cardiotocography (the so-called "trace", which is also done at term of pregnancy to evaluate fetal well-being) and from doppler of the umbilical arteries. Some centers also use the doppler of the venous duct, the use of which gave interesting results in a clinical study conducted a few years ago, but which not all specialists consider fundamental.

Iugr, prevention

On the prevention front, the only pharmacological tool we have is theaspirinetta (500 milligrams per day), recommended for women at risk of having a pregnancy with fetal growth retardation, for example because they are at risk of preeclampsia or because they have already had a pregnancy with severe Iugr.

"But be careful, it can only be useful if started in the first trimester of pregnancy, when the placenta is being formed, and its effectiveness is in any case limited "he clarifies.

"For the rest, precisely because we know that the risk of Iugr is linked to events that occur in the very first moments of a pregnancy, as well as in the period preceding it, it is very important to try to have a lifestyle as healthy as possible in the months leading up to conception. Both women and men should have a diet rich in antioxidants and low in oxidants, do not drink alcohol, do not smoke ".

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The perspectives of research

There is no doubt that fetal growth retardation represents a clinical problem seeking solution. The ideal would be to have drugs capable of "fixing" what is wrong, restarting growth in the uterus, and in recent years some approaches have begun to emerge that try to go in this direction.

One of these was much talked about a few weeks ago, due to a Dutch clinical study that was interrupted due to the death of some newborns. The study aimed to evaluate the utility in severe IUGR of a molecule called Sildenafil, better known under the trade name of Viagra, comparing it to a placebo. The basic idea is simple: since Viagra causes blood vessels to dilate, its administration in the presence of fetal growth retardation could have led to dilation of the placental vessels, providing more oxygen and nutrients to the fetus.

Unfortunately, however, things did not go as hoped. On the contrary: at a certain point it was realized that among the children born to women treated with the drug, a condition - pulmonary hypertension - particularly serious and in some cases fatal, seemed more frequent. It affected 17 children whose mothers were treated with the drug (and 11 died), compared with 3 children of women treated with placebo (no deaths). In reality, this difference between the two groups is not necessarily significant: the sample of women participating in the study was small, and in these conditions the fact that serious side effects occurred more frequently among treated women could simply be a case, but it is clear that the experimentation could not continue.

On the other hand, according to the very idea behind this study, it was not so strong, and not only because it is very difficult to implement decisive interventions when the placental damage it is now done. "This and other approaches aim to increase the oxygen flow to the fetus, but if oxygen begins to arrive in greater quantities than the cells are able to metabolize, other damage can even be created. Too much oxygen, in fact, means more free radicals and therefore more inflammation ".

Meanwhile, other research groups are studying other strategies. For some years now, the group has focused on a molecule called IGF-BP which is altered in the presence of placental malfunctions and could represent a target for new therapies. And still others focus on stem cells or gene therapy.

"For sure it will take a long time to develop these types of approaches, and a great many preclinical studies, that is, in the laboratory and on animal models "he comments. Moreover, there is always a lot of reluctance to conduct clinical studies with pregnant women. A reluctance that is partly justified, but which must be overcome in some way if we want to have access to truly effective therapeutic tools.

"A working group of the American National Institute of Child Health and Human Devolopment recently pointed out this, suggesting that it should really change the way of seeing, from a clinical point of view, the population of pregnant women. fragile population in which it is better to avoid any therapy, but as a population in need for which to seek effective therapies, because at the moment there are very few of them ".

Read also: The development of the fetus in the 40 weeks

Questions and answers

What does Iugr mean?

Iugr is the abbreviation for intrauterine growth retardation (or restriction). In practice, it is a fetus that is not growing as it should.

When does a child have stunted growth?

When at birth it did not reach its growth potential, that is, it did not grow as much as it could and should have if all its potential had found the right conditions to express itself.

  • iugr
  • growth retardation
  • preeclampsia
  • weeks 14 28
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