What is selective intrauterine growth restriction (sIUGR)?
Selective intrauterine growth restriction is present when the fetal weight of one twin is below the 10th percentile  in one
twin of a monochorionic twin pregnancy while the co-twin is of normal size . sIUGR affects 12 - 25 % of monochorionic
and is thought to be caused by unequal sharing of the placenta by the twins  .
In growth restricted fetuses ultrasound Doppler velocimetry is used to
evaluate the hemodynamic status of the fetus. Pulsed Doppler is performed on the umbilical arteries (UAs) in a free loop of umbilical cord, with the
angle of insonation as near to zero as possible, in the absence of fetal and
maternal breathing . The figures below show three main patterns of blood flow that can be detected.
Gratacós E, et. .al have suggested fetuses with sIUGR may be classified into three types based on one of three main
umbilical artery Doppler waveform patterns, as defined by the characteristics of diastolic flow: positive, persistently absent/reversed or intermittently absent/reversed .
Classification of sIUGR :
- Type I (positive end-diastolic flow in the umbilical artery)
Type II (AREDF) : persistently absent or reversed end-diastolic flow
Type III (iAREDF). intermittent absent or reversed end-diastolic flow in the
absence of fetal breathing.
Using the above classification system Gratacós E et. al. followed 134 MC twins diagnosed with sIUGR.
Fetal well-being was monitored by serial evaluation of Doppler
waveforms in the umbilical arteries , middle cerebral artery and ductus
venosus, in combination with fetal biophysical profile,
and, from 28 weeks’ gestation onwards, fetal heart
Hospital admission was contemplated beyond 28 weeks if there was persistent AREDF in the UA Doppler examination,
brain-sparing effect or abnormal ductus venosus Doppler flow. The management protocol considered the option of fetoscopy-guided cord occlusion in the smaller twin if severe fetal
deterioration was observed before 28 weeks.
Fetal deterioration indicating the need for active management was defined as
the presence of :
Before 28 weeks:
- Absent or reversed atrial flow in
the ductus venosus (DV) *
After 28 weeks:
Any of the following:
- Persistent reversed end-diastolic flow in the umbilical artery
- Ductus venosus pulsatility index (PI) persistently above two SD for
- AND/OR persistently abnormal fetal heart rate
The table below shows the prevalence of some selected adverse events found by Gratacós E and co-workers according
to the type of sIUGR
* The duration of absent or
reversed flow during atrial systole in the DV has been found to be a strong
predictor of stillbirth [5,6 ]
Type of sIUGR
Prevalence of selected
adverse events 
Unexpected fetal death
Parenchymal brain lesion larger twin
Parenchymal brain lesion in smaller twin
In the Fetus with IUGR The Society for Maternal-Fetal Medicine
"When Doppler abnormalities are detected in the fetal arterial circulation,
weekly follow-up Doppler studies are considered usually sufficient if forward
umbilical artery end-diastolic flow persists. In the absence of specific data
regarding the optimal frequency of testing, experts have recommended Doppler
surveillance up to 2-3 times per week when IUGR is complicated by
oligohydramnios, or absent or reversed umbilical artery end-diastolic flow."
- Twice weekly nonstress testing with weekly
amniotic fluid evaluation, or weekly biophysical profile testing, is
commonly recommended when IUGR is suspected
- Antenatal corticosteroids should be administered
if absent or reversed end-diastolic flow is noted <34 weeks in a
pregnancy with suspected IUGR.
Delivery of monochorionic diamniotic twins with
isolated fetal growth restriction at 32 0/7–34 6/7 weeks of gestation
is recommended .
Presently there is no treatment for sIUGR . At early gestational ages
cord occlusion (radiofrequency ablation needle) or fetoscopic placental laser
coagulation has been offered when the risk of death in the sIUGR twin is very
high or imminent in order to prevent brain and other organ damage to the
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2. Gratacós E, et. .al. A classification system for selective intrauterine
growth restriction in monochorionic pregnancies according to umbilical artery
Doppler flow in the smaller twin.
Ultrasound Obstet Gynecol. 2007 Jul;30(1):28-34.
3. Society for Maternal-Fetal Medicine Publications Committee, Berkley E,
Chauhan SP, Abuhamad A.Doppler assessment of the fetus with
intrauterine growth restriction.Am J Obstet Gynecol. 2012 Apr;206(4):300-8. doi: 10.1016/j.ajog.2012.01.022.
Erratum in: Am J Obstet Gynecol. 2012 Jun;206(6):508. Am J Obstet Gynecol. 2015
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4. Medically indicated late-preterm and early-term deliveries. Committee
Opinion No. 560. American College of Obstetricians and Gynecologists. Obstet
Gynecol 2013;121:908–10. PMID:23635709
5. Turan OM, et. al., Duration of persistent abnormal ductus venosus flow and
its impact on perinatal outcome in fetal growth restriction.Ultrasound Obstet
Gynecol. 2011 Sep;38(3):295-302. doi: 10.1002/uog.9011.PMID:21465604
6. Morris RK, et. al., Systematic review and meta-analysis of the test
accuracy of ductus venosus Doppler to predict compromise of fetal/neonatal
wellbeing in high risk pregnancies with placental insufficiency.
Eur J Obstet Gynecol Reprod Biol. 2010 Sep;152(1):3-12. doi:
10.1016/j.ejogrb.2010.04.017. Epub 2010 May 20. PMID:20493624