Intrauterine Growth Restriction

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Introduction

Intrauterine growth restriction (IUGR) describes babies who are small for gestational age. This commonly defined as a weight below the 10th percentile of what is expected for gestational age.

 

It is "one of the common and complex priblems

8-10% in dev

up to 23% in low-resource countries

It is a major contributor to perinatal morbidity and mortality, leading to asphyxia, impaired thermoreg, nec, kidney damage, lung disease, and SIDS (Manning et al, 1995.)

In adult life, IUGR is associated with metabolic syndrome

 

 

Diagnosis

Important to diagnose antepartum IUGR.

 

Diagnosis is not clear, commonly defined as weight below 10% percentile. However, this does not take into account constitutional factors, leading to false positive diagnosis.

It also requires a reference.

A newer approach incorporates individual factors, by stating 'a fetus that has not reached it's growth potential".

Gestation.net

 

 

The Case of Baby Arun

Arun is a boy born at 37 weeks gestational age. His birth weight is x, placing him at the 6% percentile. His head appears to be proportional.

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Causes and Risk Factors

There are many potential causes of IUGR, and an initial approach to diagnosis depends on symmetry. Asymmetric infants have a relatively normal head circumference but small length and weight, while symmetric infants are small in all parameters. Asymmetry points towards maternal or placental issues, whereby insufficent nutrients reach the fetus, and those that do are preferentially used for head development. Symmetry suggests the growth restriction lies within the fetus (Campbell et al, 1977).

Asymmetrical growth restriction

maternal

  • hypertension or pre-eclampsia
  • diabetes
  • chronic disease
  • smoking
  • illegal drug use

placenta

  • placental abruption
  • placenta previa
  • abnormal placentation

 

Symmetrical growth restriction

congenital infections (TORCHES)

  • Toxoplasma
  • Rubella
  • CMV
  • Herpes Simplex
  • Syphilis

chromosomal abnormalities

chemical exposure

constitutional small size

 

However, there is an increasing sentiment that this classification may not be ideal, and that comparison of blood flow via ultrasound dopplers (see below) may provide more helpful

 

Placental issues

Fetal

  

 

 

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Pathophysiology

Normal fetal growth is poorly understood, but is known to include endocrine regulation (IGF 1&2)

Normal fetal growth includes hyperplasia in the first 16 weeks. The fetus grows at 5 g/day at 15 weeks.

 

The normal placenta sees trophoblastic invasion by spiral arteries, creating a low resistance circulation on the maternal circulation.

If the placenta is functioning poorly, oxygen flow is preferentially shunted to the brain, kidneys, etc.

 

The fetal circulation contains three main shunts:

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Signs and Symptoms

  • history
  • physical exam

History

The goal of prenatal care is to identify and treat risk factors for poor outcomes

 

Review the maternal history of health and pregnancy. Specifically inquire into:

  • infections, especially during the first trimester

Family history

  • chromosomal abnormalities

Social history

  • smoking status
  • exposure to chemicals

Physical Exam

Track syphysis to fundal height throughout pregnancy (only 25-50% detection)

Examine the placenta at time of delivery.

Carefuuly measure the weight, length, and head circumference.

Perform a physical exam of the infant to identify any abnormalities, paying particular attention to the heart, lungs, skin, and neurological systems.

Eye exam may reveal cataracts.

Dysmorphic features of the face, ears, and limbs may suggest chromosomal issues.

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Investigations

  • lab investigations
  • diagnostic imaging
  • fetal surveillance

Lab Investigations

If no clear cause is found, bloodwork may be performed to investigate for infections. This can include:

  • CBC
  • liver enzymes
  • IgM antibodies for specific infectious agents
  • blood gases for metabolic acidosis

Diagnostic Imaging

An early dating u/s is important for accurate GA (using crown-rump length)

If concern is present, do ultrasound to assess:

  • bpd
  • abdomen (most important)
  • femur length
  • fluid volume (oligohydramnios vs polyhydramnios)

Doppler may be used to assess placental development.

The umbilical and middle cerebral arteries

Fetal Surveillance

Fetal surveillance depends on the particular situation

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Treatments

Prenatal

Various interventions have been attempted, with poor demonstration of value. These include:

 

Delivery

If there is strong concern, delivery should be expidited. However, deliver a premature infant carries risk of it's own. As such, delivery should be carried out if the risk of fetal death exceeds the risk of neonatal death.

Fetuses below 34 weeks GA should be treated with corticosteroids to improve fetal lung development.

One algorithm is provided in the Journal of Perinatal Medicine, 2010.

 

 

 

 

Neonatal

Infants should be monitored and treated for hypoglycemia. Adequate nutrition should be provided.

Symmetrical growth retardation is usaually treated supportively, paying close attention to blood sugars and temperature.

may be treated in some cases. These include:

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Consequences and Course

Infants who are small due to maternal or placental issues (assymetric growth restriction) in general do very well.

Symmetrically small infants fare less well, given the severity of many of the causes and a lack of effective treatments.

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Resources and References

 

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Topic Development

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