The document summarizes two articles from the March 2014 issue of the Ultrasound in Obstetrics and Gynecology journal club. The first article compares the performance of traditional fetal growth charts versus a probabilistic model using biometry at 31-34 weeks to screen for small-for-gestational age fetuses in low-risk pregnancies. The probabilistic model had slightly better accuracy and allowed incorporation of maternal factors. The second article found that appropriate for gestational age fetuses in lower birth weight quartiles exhibited Doppler changes suggesting placental insufficiency and failure to reach growth potential, challenging the view that only small fetuses face these risks.

1. UOG Journal Club: March 2014
Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
J. J. Stirnemann, G. Benoist, L. J. Salomon, J.-P. Bernard and Y. Ville
Volume 43, Issue 3, Date: March 2014, pages 311-316
Changes in fetal Doppler indices as a marker of failure to reach
growth potential at term
J. Morales-Roselló, A. Khalil, M. Morlando, A. Papageorghiou,
A.Bhide and B. Thilaganathan
Volume 43, Issue 3, Date: March 2014, pages 303-310
Journal Club slides prepared by Dr Aly Youssef
(UOG Editor for Trainees)

2. UOG Journal Club: March 2014
Optimal risk assessment of small-for-gestational-age
fetuses
using 31–34-week biometry in a low-risk population
J. J. Stirnemann, G. Benoist, L. J. Salomon,
J.-P. Bernard and Y. Ville
Volume 43, Issue 3, Date: March 2014, pages 311-316

3. Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
Stirnemann et al., UOG 2014
Introduction
• Late-pregnancy intrauterine growth restriction (IUGR) remains a
leading cause of unanticipated perinatal death and morbidity
after 34 weeks’ gestation
• The detection and follow-up of fetuses at risk are necessary for
optimal management and planning of delivery
• Estimated fetal weight (EFW) using a cross-sectional agespecific percentile as a selection criterion of altered growth
remains the most widely used method to prenatally assess the
likelihood of IUGR

4. Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
Stirnemann et al., UOG 2014
Objective
To compare the performance of traditional growth charts for
EFW and a validated pragmatic probabilistic approach using
biometry at 31–34weeks’ gestation to screen for late
pregnancy small-for-gestational age (SGA) fetuses in
a low-risk population.

5. Methods
Training dataset
•Records of 7755 women presenting at 31–34 weeks following normal
aneuploidy screening in the 1st or 2nd trimester, and normal 20-24 wks
scan.
•Only cases with known birth weight and gestational age at delivery, with
gestational age at delivery ≥37 weeks were included.
•Prenatal and postnatal malformations and cases with absent or reversed
diastolic flow in the umbilical artery were excluded.
Validation dataset
•1725 women recruited at 11-14 weeks onwards.
•
At 31-34 weeks biparietal diameter, head circumference, abdominal
circumference and femur length were measured.

6. Methods
Defining SGA
•Analysis of data was conducted for different definitions of SGA including birth
weight <3rd, 5th, and 10th centiles, and birth weight <2500 grams.
The probabilistic model
•
A logistic regression model was built for each type of ultrasound
measurement, computed using locally-derived growth charts.
•
The results were displayed in terms of false-positive rate and detection rate
of SGA, bypassing the intermediate step of EFW calculation.
•
The potential additional value of maternal characteristics such as smoking
status, parity, body mass index (BMI) and age were also investigated.
•
External validation was performed by comparing observed prevalence and
predictions given by the model in the second independent dataset.
This model was compared with the routinely used multistep approach involving
estimation of fetal weight and consecutive screening by a percentile cut-off.

7. Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
Stirnemann et al., UOG 2014
Results
Accuracy of predicting birth weight <10th centile
Probabilistic
approach
Area under the
ROC curve
Model using EFW
P value
0.832
0.828
0.007
•
For a 10% false-positive rate, the probabilistic approach yielded a 51%
detection rate for birth weight<10th centile, compared to the 32% and
48% detection by the 10th centile cut-off of two EFW reference charts.
•
Adding maternal characteristics significantly improved detection of SGA
by 2%, from 51% to 53%.

8. Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
Stirnemann et al., UOG 2014
Conclusion
• As the main goal of ultrasound biometry is to detect abnormal growth,
the suggested probabilistic model using biometric measurements seems
a reasonable and pragmatic approach.
• This may unify screening procedures and simplify counselling at 31-34
weeks.
• In addition, it allows the direct incorporation of maternal-specific
characteristics, thus having the potential to replace customized growth
charts.
• This screening strategy is however intended for low-risk population and
is not validated in high risk pregnancies, or outside the 31-34 weeks
window.

9. Optimal risk assessment of small-for-gestational-age fetuses
using 31–34-week biometry in a low-risk population
Stirnemann et al., UOG 2014
Weaknesses
• Some important maternal covariates, such as ethnicity, were
not recorded.
• The sample size may still limit the accuracy of parameter
estimation for very low birth weights.
• This approach is not validated for high risk pregnancies.

10. Discussion points
•
Should low-risk women be offered an ultrasound scan with fetal
weight estimation in the third trimester?
•
Would the probabalistic method be superior to the use of
customized growth charts to detect SGA at term?
•
Which cut-off of estimated fetal weight/fetal biometric
measurements should be used to define IUGR?
•
How should pregnancies with SGA fetuses at term with normal
Doppler indices be managed?
•
How should pregnancies with AGA fetuses at term with abnormal
Doppler indices be managed?

11. UOG Journal Club: March 2014
Changes in fetal Doppler indices as a marker of failure to
reach growth potential at term
J. Morales-Roselló, A. Khalil, M. Morlando, A.
Papageorghiou, A. Bhide and B. Thilaganathan
Volume 43, Issue 3, Date: March 2014, pages 303-310

12. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Background
SGA = fetus with EFW <10th centile (i.e. small-for-gestational age).
FGR = fetus unable to achieve its genetically determined size as a
consequence of placental insufficiency (typically defined as SGA with
evidence of placental insufficiency.
• The standard definitions of both SGA and FGR exclude apparently
appropriate for gestational age (AGA) infants that are growth
restricted (e.g. birth-weight (BW) on the 40th centile with genetic
potential to be born on the 80th centile).
• To date, the identification of AGA fetuses affected by occult chronic
placental insufficiency, fetal hypoxemia and failure to reach growth
potential (FRGP) remains challenging.

13. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Objective
To determine whether AGA fetuses at term exhibit changes in
middle cerebral artery (MCA) and umbilical artery (UA) Doppler
indices that may be of value in identifying those that are
affected by placental insufficiency and subsequent FRGP.

14. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Methods
Retrospective cohort in a tertiary centre from 2002-2012.
Inclusion criteria
•Singleton pregnancies.
•Morphologically normal and term fetuses.
•Ultrasound performed within 14 days before date of
delivery.
•
•
•
•
•
Exclusion criteria
•Fetal abnormality.
•Aneuploidy.
•Antepartum stillbirth.
UA and MCA were examined using color Doppler and the pulsatility index
(PI) was measured.
Cerebroplacental ratio (CPR) was calculated = MCA PI / UA PI.
All Doppler indices were converted into multiples of the median (MoM) for
gestational age.
Doppler PI MoM values were represented in scatter graphs according to BW
centile, and linear regression analysis was calculated evaluating the
presence of statistical significance.
Doppler measurements were then grouped according to BW quartiles and
compared.

15. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Methods
• As the group of largest fetuses (>90th centile) was assumed
to include those least likely to be FRGP, the CPR 5th centile
from this group (optimal CPR) was preliminarily established
as the normality threshold to indicate placental insufficiency.
• The proportion of fetuses with FRGP was estimated in each
group by subtracting the proportion of fetuses with a CPR
below this optimal CPR limit.

16. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Results
Cerebroplacental ratio MoM
MCA PI/UA PI MoM
Linear regression analysis showed
that AGA fetuses with lower
BW centiles had significantly:
1.higher UA PI MoM
2.lower MCA PI MoM
3.lower CPR MoM
BW centiles

17. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Results
Cerebroplacental
ratio MoM intervals
Compared to fetuses >75th BW
centile, AGA fetuses in the
CPR MoM
lower quartiles had lower CPR
MoM, suggesting that some of
these pregnancies were
affected by placental
insufficiency and FRGP.
BW centiles

18. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Results: proportion of fetuses with failure to reach growth potential (FRGP)
Proportion of fetuses with FRGP
(% of fetuses with FRGP were calculated after subtracting those cases with CPR MoM <5th
centile observed in the group with BW >90th centile)
BW centile
75-90th centile
1%
50-75th centile
1.7%
25-50th centile
2.9%
10-25th centile
BW centile groups
% of fetuses with
FRGP
6.7%

19. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Discussion
•
The data presented in this study demonstrate that in term AGA pregnancies,
Doppler indices suggestive of fetal hypoxemia are more prevalent in the lower
AGA BW centiles.
•
The study findings imply that Doppler indices have the potential to identify AGA
fetuses that are affected by placental insufficiency and failing to reach their
genetic growth potential, as evidenced by blood flow redistribution.
•
This finding challenges the conventional paradigm that only SGA fetuses are at
risk of placental insufficiency, fetal hypoxemia and FRGP.
•
It is still unknown whether the degree of placental insufficiency leading to FRGP
in these AGA fetuses is predictive for perinatal complications and childhood
developmental problems as seen in SGA and IUGR neonates.

20. Fetal doppler changes as a marker of failure to reach growth potential at term
Morales-Roselló et al., UOG 2014
Future perspectives
Future studies are needed to evaluate the performance of the CPR in
AGA fetuses in the prediction of neonatal neurodevelopmental
impairment, with the aim of optimizing the timing of delivery and
reducing long-term neonatal handicap.
Discussion points
• How should women at term with appropriate for gestational age fetuses
and evidence of circulatory redistribution be managed?
• Which cut-off of cerebroplacental ratio should be used to define fetal
blood flow redistribution?
• Should middle cerebral artery and umbilical artery be performed in
women with appropriate for gestational age fetuses?