Intrauterine Growth Restriction and its Management

The Thrifty Phenotype Hypothesis​

Also called as the Barkers Hypothesis, after its postulator – David Barker, this hypothesis elucidated that impaired fetal growth could play an important role in the emergence of coronary heart disease and its other metabolic precursors the individual in his/her later life.1

Barker and his team correlated the death records to the persons’ birth and infant weights collected during the 1920s and 1930s and proposed this theory. Nevertheless, his theory was criticized for the inadequate attention to environmental, genetic and socioeconomic, confoundings; and other methodological factors that could threaten the hypothesis. Despite its shortcomings, it is still one of the popular hypothesis which resulted in a cascade of both animal and human trials.1

Intrauterine Growth Restriction ​

Any infant weighing less than 5 pounds, 8 ounces (2,500 grams) falls under the low birth weight category. Premature birth and Intrauterine Growth Restriction (IUGR) are the primary causes of low birth weight newborns.2 Any aberration disrupting the normal biological processes during the course of pregnancy gives rise to IGUR, stunting the growth of the fetus. Depending on the occurrence of the aberration during pregnancy, IGUR can be categorized as being either symmetric or asymmetric (Figure 1)3

The burden of IUGR is seen mostly in in Asian countries accounting for nearly 75% of all affected infants. Although the Indian statistics, show a 26% prevalence of Low Birth Weight (LBW), the prevalence of IUGR has been found to be 54%.3

Diagnosis

The diagnosis of IUGR is a two-step procedure:

1) Identification of the growth restriction by ultrasonography

2) Identification of an underlying factor causing IGUR

Crown Rump Length (CRL) through ultrasound in early pregnancy is the best way to detect the gestational age (GA). After determining the GA, serial ultrasound biometrics such as clinical palpation, Fundal Height (FH) measurement and ultrasonic fetal biometry, can be employed to see if the fetus is reaching its growth potential.4

Post diagnosis, it must be identified to which etiological group the fetus falls into. Usually placental conditions are the most common etiology of IUGR. (Table 1)

The risk factors which could cause low birth weight:2

  1. Infection during pregnancy
  2. Insufficient weight gain during pregnancy
  3. Previous pregnancy with a low-birth-weight baby
  4. Smoking
  5. Alcohol or drug use
  6. Pregnancy at less than 17 or more than 35 years

                                                                  Table 1. Etiological groups4

Small fetuses but otherwise healthy

An abnormal condition such as a maternal condition

An existing fetal condition

An existing placental condition

Constitutional small, and therefore not growth-restricted

Could be due to chronic hypertension, pre-gestational diabetes, cardiovascular disease, substance abuse, autoimmune conditions, infections such as malaria, etc.

Could be an infection, malformation, chromosomal aberration, etc.

Could be chorioangioma, infarction, circumvallate placenta, confined placental mosaicism, obliterative vasculopathy of the placental bed, etc.

Progressive research is ongoing which aims to find out the methods for effective prevention of IUGR. Simple means for preventing this problem are not being considered given the multifactorial nature of IUGR. It must be understood that in about 30% of IUGR, Chronic Fetal Hypoxemia (CFH) is observed which suggests that prevention of the adverse consequences could be possible after the diagnosis of IUGR w28x. It is evidenced that the improvement of perinatal outcome was observed by optimizing the timing of the delivery.4

Nevertheless, an intervention has been demonstrated which decreases neonatal morbidity and mortality is the administration of steroids to premature fetuses during parturition. Bernstein et al reported the effects of administering the maternal prenatal glucocorticoid in growth-restricted fetuses and found that the benefits are similar to those found in gestational age-matched, normally grown fetuses. The team concluded that IGUR within the range of 500-1500 g birth weight is associated with the increased risks of neonatal death and respiratory distress syndrome which can be decreased potentially by the administration of a prenatal corticosteroid. Odds ratio reduction with steroids, from Bernstein et al, is as follows. (Table 2)5

                                              Table. 2 Results with Odds ratio reduction with steroids5

Complication

Relative risk

95%  Confidence Interval

Death

0.54

0.48-0.62

Respiratory distress syndrome

0.51

0.44-0.58

Intraventricular hemorrhage

0.67

0.61-0.73

Intravascular hemorrhage

0.5

0.43-0.57

Necrotizing enterocolitis

No difference

No difference

Categorization and management of IUGR on the basis of the ultrasound findings and gestational age4

Category 1

Category 2

Category 3

Category 4

Category 5

IUGR with normal umbilical artery Doppler waveforms

and reassuring tests of fetal well-being

IUGR with umbilical artery PI>2 SD above the mean for gestational age, presence of diastolic flow and

reassuring tests of fetal well-being

IUGR with umbilical artery PI>2 SD above the mean for gestational age, presence of diastolic flow and

non-reassuring tests of fetal well-being

IUGR with umbilical artery absent diastolic flow. Tests of fetal well-being are usually non-reassuring

IUGR with the reversed diastolic flow in the umbilical artery. Tests of fetal well-being are nearly always nonreassuring.

– Serial biometry, umbilical Doppler and tests of

fetal well-being

A. GA >34 weeks.

– Umbilical artery Doppler and tests of fetal well-being twice weekly. The decision for delivery is based on test results. Trial of labor for

vaginal delivery is acceptable.

A. GA >34 weeks.

– Daily umbilical artery Doppler and daily tests

of fetal well-being. Consider delivery. Trial of

labor for vaginal delivery is acceptable.

A. GA >34 weeks.

– Consider delivery

 

A. GA >34 weeks.

– Extensive counseling on mortality and morbidity.

Active or expectant management

according to the choice of the family.

 

B. GA<34 weeks.

– Umbilical artery Doppler and tests of fetal well-being twice weekly. Consider corticosteroid

administration for fetal lung maturation. The decision for delivery is based on test results. Trial of labor for vaginal delivery is acceptable.

B. GA <34 weeks.

– Corticosteroid administration for fetal lung

maturation. Daily umbilical artery Doppler and

daily tests of fetal well-being. Consider delivery

Trial of labor for vaginal delivery is

acceptable.

B. GA<34 weeks.

– Corticosteroid administration for fetal lung maturation. Consider delivery.

B. GA<34 weeks.

– Extensive counseling on mortality and morbidity.

Active or expectant management

according to the choice of the family in concert

with the obstetric and neonatal teams.

Corticosteroid administration for fetal lung maturation.

PI: Pulsality Index; IGUR: Intrauterine Growth Restriction; GA: Gestational Age

Reference:

  1. Barker Hypothesis. In BoslaughS. editor. Encyclopedia of epidemiology. California: SAGE Publications, Inc; 2008.
  2. University of Rochester Medical Center Rochester, NY. Low birth weight [Internet] [cited 2020 May 10]. Available from https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02382
  3. SaleemT, et al. Intrauterine growth retardation – small events, big consequences. Ital J Pediatr. 2011; 37: 41.
  4. Mandruzzato et al. Intrauterine restriction (IUGR). Recommendations and guidelines for perinatal practice. J. Perinat. Med. 2008;36:277–281
  5. Bernstein IM, et al. Morbidity and mortality among very-low-birth-weight neonates with intrauterine growth restriction. The Vermont Oxford Network. Am J Obstet Gynecol. 2000;182(1 Pt 1):198-206

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