SGA and IUGR

SGA and IUGR
By Tina Burleson Stewart, MD

What is the difference between SGA and IUGR?
Can these terms be used interchangeably?
SGA - small for gestational age infants
* an infant whose weight is lower than the population norms
* defined as weight below 10th percentile for gestational age or greater than 2 standard deviations below the mean
* cause may be pathologic or nonpathologic

IUGR - intrauterine growth retardation
* defined as failure of normal fetal growth
* caused by multiple adverse effects on fetus
* due to process that inhibits normal growth potential of fetus


So what is the difference between SGA and IUGR?
* These terms are related but not synonomous.
* Not all IUGR infants are small enough to fit the qualifications for SGA.
* Not all SGA infants are small because of a growth-restrictive process, and therefore, do not meet criteria for IUGR.

Incidence
* 3-10% of all pregnancies
* 20% of stillborn infants
* perinatal mortality 4-8 times higher
* half have serious or long-term morbidity

Epidemiology
* more common in low socioeconomic class
* more common in those of African-American race
* leading cause in third world countries is inadequate nutrition of mother
* leading cause in US is uteroplacental insufficieny

Causes of IUGR
* maternal factors
* fetal factors
* placental factors
* environmental factors

Maternal causes of IUGR
* inadequate nutrition of mother
* multiple gestation
* uteroplacental insufficiency
* hypoxia
* drugs

Mother’s Malnutrition
* lack of adequate food supply
* poor weight gain
* chronic illness
* malabsorption

Multiple Gestation
* difficult to provide optimal nutrition for greater than one fetus
* uterine capacity limitations

Uteroplacental Insufficiency
* preeclampsia
* chronic HTN
* renovascular disease
* vasculopathy from diabetes
* drugs

Hypoxia
* maternal hemoglobinopathies - sickle cell
* maternal anemia
* maternal cyanotic heart disease
* mom living at high altitudes

Maternal Drug Use and Toxin Exposure
* cigarettes
* cocaine
* amphetamines
* antimetabolites - MTX
* bromides
* heroin
* hydantoin
* isoretinoin (Accutane)
* methadone
* alcohol
* methyl mercury
* phencyclidine
* phenytoin (Dilantin)
* polychlorinated biphenyls
* propanolol
* steroids - prednisone
* toluene
* trimethadione
* warfarin (Coumadin)

Fetal Causes of IUGR
* genetics
* congenital infection
* inborn errors of metabolism

Chromosome Disorders associated with IUGR

* trisomies 8, 13, 18, 21
* 4p- syndrome
* 5p syndrome
* 13q, 18p, 18q syndromes
* triploidy
* XO - Turner’s syndrome
* XXY, XXXY, XXXXY
* XXXXX

Syndromes associated with low birth weight
* Aarskog-Scott syndrome
* anencephaly
* Bloom syndrome
* Cornelia de Lange syndrome
* Dubowitz syndrome
* Dwarfism (achondrogenesis, achondroplasia)
* Ellis-van Creveld syndrome
* Familial dysautonomia
* Fanconi pancytopenia
* Hallerman-Streiff syndrome
* Meckel-Gruber syndrome
* Microcephaly
* Mobius syndrome
* Multiple congenital anomalads
* Osteogenesis imperfecta
* Potter syndrome
* Prader-Willi syndrome
* Progeria
* Prune-belly syndrome
* Radial aplasia; thrombocytopenia
* Robert syndrome
* Robinow syndrome
* Rubinstein-Taybi syndrome
* Silver syndrome
* Seckel syndrome
* Smith-Lemli-Opitz syndrome
* VATER and VACTERL
* Williams syndrome

Congenital Infections associated with IUGR
* rubella
* cytomegalovirus
* toxoplasmosis
* herpes
* syphilis
* varicella
* hepatitis B
* coxsackie
* Epstein-Barr
* parvovirus
* Chagas disease
* malaria

Metabolic disorders associated with low birth weight
* agenesis of pancreas
* congenital absence of islets of Langerhans
* congenital lipodystrophy
* galactosemia
* generalized gangliosidosis type I
* hypophosphatasia
* I cell disease
* leprechaunism
* maternal and fetal phenylketonuria
* maternal renal insufficiency
* maternal Gaucher disease
* Menke syndrome
* transient neonatal diabetes mellitus

Placental Causes of IUGR
* placental insufficency
o very important in the 3rd trimester
* anatomic problems
o infarcts
o aberrant cord insertions
o umbilical vascular thrombosis
o hemangiomas
o premature placental separation
o double vessel cord
* microscopic changes
o villous necrosis
o fibrinosis

Environmental Causes of IUGR
* high altitude - lower environmental oxygen saturation
* toxins

IUGR classification
* SYMMETRIC
* height, weight, head circ proportional
* early pregnancy insult: commonly due to congenital infection, genetic disorder, or extrinsic factors
* normal ponderal index
* low risk of perinatal asphyxia
* low risk of hypoglycemia
* ASYMMETRIC
* head=height, both > weight
* brain growth spared
* later in pregnancy: commonly due to uteroplacental insufficiency, maternal malnutrition, hypoxia, or extrinsic factors
* low ponderal index
* increased risk of asphyxia
* increased risk of hypoglycemia

Ponderal Index
* The ponderal index is used determine those infants whose soft tissue mass is below normal for their stage of skeletal development. Those who have a ponderal index below the 10th % can be classified as SGA.
* Ponderal Index = birth weight x 100 crown-heel length

Diagnosis
Prior to delivery, it is necessary to determine the correct gestational age.
* last menstrual period - most precise
* size of uterus
* time of quickening (detection of fetal movements)
* early ultrasound - the earlier the better accuracy
o biparietal diameter
o abdominal circumference - best sensitivity
o ratio of head to abdominal circumference
o femur length
o placental morphology and amniotic fluid

Diagnosis after delivery (OUR JOB!)
* low birth weight - this parameter alone misses big IUGR infants and overdiagnoses constitutionally small infants
* appearance - thin with loose, peeling skin; scaphoid abdomen; disproportionately large head; may be dysmorphic
* ponderal index
* Ballard/Dubowitz - accurate within 2 weeks of gestation if birth weight >999g, most accurate within 30-42 hrs of age
* birth/weight curves

Complications
* hypoxia
o perinatal asphyxia
o PPHN
* hematologic - polycythemia
* meconium aspiration
* metabolic
o hypoglycemia
o hypocalcemia
o acidosis
* hypothermia
* neurological
o more tremulous
o more easily startled
o less visual fixation
o less activity
o less oriented to visual and auditory stimuli

Management in utero
* serologic testing if desired by parents
* decrease mother’s activity
* stop or decrease risk factors if possible
* closely monitor with biophysical profile or nonstress testing or amniotic fluid measurements
* ultrasound every 10-21 days
* teach mom fetal kick counting
* deliver if reaches 36 weeks

Management after birth
* obtain history of risk factors
* appropriate resuscitation
* prevent heat loss
* watch for hypoglycemia
o check glucoses
o early feeding
o parenteral dextrose
* check hematocrit
* screen for congenital infections
* screen for genetic abnormalities
* check calcium

Outcome

* depends on cause of IUGR/SGA and neonatal course
* symmetric IUGR - poor outcome because early insult
* asymmetric IUGR - better outcome because brain spared
* very bad if brain growth failure starts at < 26 weeks
* school performance influenced by social class
* 25-50% likelihood of neurodevelopmental problems


SGA and IUGR.ppt