TY  - CHAP
M1  - Book, Section
TI  - Intrauterine Growth Restriction
A1  - Malcolm, William F.
PY  - 2015
T2  - Beyond the NICU: Comprehensive Care of the High-Risk Infant
AB  - DefinitionBirthweight  is  a  measure  of  fetal  growth  in  pregnancy  but  is  imprecise  because  it  represents  fetal  growth  at  only  one  time  point,  at  the  end  of  gestation.  Birthweight  provides  limited  insight  into  the  fetal  growth  pattern  throughout  gestation.Low  birthweight  (LBW)  is  defined  as  a  birthweight  less  than  2500  g  but  does  not  take  gestational  age  into  consideration.  Thus,  some  babies  who  are  classified  as  LBW  may  in  fact  be  normally  grown  because  they  are  preterm.  Similarly  the  descriptor  of  very  low  birthweight  (VLBW),  defined  as  less  than  1500  g  at  birth,  will  include  a  number  of  babies  of  older  gestation  with  poor  growth  in  utero.Intrauterine  growth  restriction  (IUGR)  is  the  failure  to  attain  optimal  intrauterine  growth,  whereas  small  for  gestational  age  (SGA)  describes  an  infant  whose  weight  is  lower  than  population  norms  (3rd,  5th,  or  10th  percentiles).SGA  infants  are  most  often  defined  as  having  a  birthweight  below  the  10th  percentile  for  gestational  age.The  ponderal  index,  defined  below,  can  be  used  to  identify  infants  whose  mass  is  below  normal  for  their  linear  development,  ie,  a  measure  of  “thinness.”  A  ponderal  index  <10th  percentile  has  been  used  to  identify  IUGR  infants  at  birth.Bithweight×100Crown−Heel  Length3Thus,  all  IUGR  infants  may  not  be  SGA,  and  all  SGA  infants  may  not  be  small  as  a  result  of  fetal  growth  restriction.Ultimately,  crossing  of  growth  centiles  in  utero  on  multiple  ultrasound  assessments  is  the  only  true  measure  of  IUGR,  but  such  information  is  rarely  available  and  so  the  proxies  described  above  are  used.IUGR  may  be  further  thought  of  as  symmetrical  or  asymmetrical.Symmetric  IUGR  occurs  when  head  circumference,  height,  and  weight  are  all  proportionately  reduced  (<10%)  for  gestational  age.  This  is  due  to  either  decreased  growth  potential  of  the  fetus  (normal  genetic  variation  or  genetic  disorders)  or  extrinsic  conditions  that  are  active  early  in  pregnancy  (metabolic  conditions,  congenital  infection,  early  nutritional  insults,  or  adverse  in  utero  conditions).Asymmetric  IUGR  occurs  when  the  head  circumference  and  length  are  closer  to  the  expected  percentiles  for  gestational  age  than  is  the  weight.  In  these  infants,  there  is  some  degree  of  sparing  of  brain  growth  relative  to  body  weight.  The  usual  causes  are  uteroplacental  insufficiency,  maternal  undernutrition  or  malnutrition,  or  extrinsic  conditions  applied  late  in  pregnancy.IncidenceLBW  affects  about  15%  worldwide  whereas  3%  to  10%  of  all  pregnancies  are  associated  with  IUGR.Estimation  of  IUGR  may  vary  based  on  the  neonatal  or  fetal  growth  charts  used  to  define  IUGR,  with  some  evidence  that  individualized  centiles  may  be  even  more  predictive.Perinatal  mortality  rates  are  four  to  eight  times  higher  for  IUGR  babies  and  ∼20%  to  80%  of  stillborn  infants  are  IUGR.  The  latter  are  due  to  the  individual  causes  of  growth  restriction  in  an  IUGR  pregnancy  and  a  failure  of  the  fetal  adaptive  responses  of  redistribution  of  fetal  blood  flow  to  key  organs  leading  to  a  decrease  in  fetal  growth  rate  (Figure  26-1)  leading  to  an  increased  risk  of  fetal  mortality.PathophysiologyIn  utero  mechanismsIUGR  in  the  human  fetus  can  be  caused  by  factors  that  are  of  maternal,  placental,  or  fetal  origin  (Figure  26-1)  including  living  at  high  altitude,  maternal  undernutrition,  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accesspediatrics.mhmedical.com/content.aspx?aid=1105545326
ER  -