Open Journal of Obstetrics and Gynecology, 2012, 2, 270-275 OJOG Published Online September 2012 (
Evaluation of thalamus echogenicity by ultrasound as
a marker of fetal lung maturity
Faris A. Rasheed1, Zahraa’ M. Al-Sattam2, Saad A. Hussain3*
1Department of Obstetrics and Gynecology, Al-Kindi Medical College, University of Baghdad, Baghdad, Iraq
2Department of Ob s tetrics, Al-Elwiya Maternity Teaching Hospital, Baghdad, Iraq
3Department of Pharmacology and Toxicology, College of Pharmacy, University of Baghdad, Baghdad, Iraq
Email: *
Received 2 June 2012; revised 6 July 2012; accepted 18 July 2012
The present study evaluated fetal thalamic echogeni-
city by ultrasound as a possible marker of fetal lung
ma tur ity in comparison with other ultrasound maker s.
A prospective longitudinal study performed in Al-
Elwiya Maternity Teaching Hospital in Baghdad,
Iraq during the period from April 2010 to March
2011. One hundred and forty two pregnant women
(36 to 42 weeks of gestation) who were admitted for
elective cesarean section and referred for an obstetric
ultrasound scan at the same day of their elective ce-
sarean section were included. Scanning with linear
ultrasound with convex transducer frequency of 3.5
MHz was utilized to measure the biparietal diameter
and the state of echogenicity was recorded as echo-
genic or echolucent, in addition to amniotic fluid
vernix and the placental changes. The presence of
echogenic thalamus as a sign of fetal lung maturity
had a specificity of 86.53% which is higher than the
three other signs of lung maturity; the positive pre-
dictive value was (89.6%) which is also higher than
the three other signs, but the sensitivity was 63.33%
and negative predictive value was 57.69% which is
lower than the presence of vernix in the amniotic
fluid, 86.66 and 67.56 respectively. In conclusion,
evaluation of echogenic thalamus is beneficial, and
can be considered as a new marker of fetal lung
maturity; however, further studies are required to
strengthen such idea.
Keywords: Fetal Lung Maturity; Thalamic Echogenicity;
Fetal lung immaturity is a major problem in the mana-
gement of elective birth with respect to predicting the
development of infant respiratory distress syndrome
(IRDS) in the neonate after birth. Although gold-standard
measures of fetal lung immaturity were the chemical,
biological and physical properties of amniotic fluid [1],
the fluid was obtained by invasive technique through
amniocentesis. Moreover, lamellar body count was eva-
luated and found to be an easy, rapid and cost-effective
as a predictive measure fetal lung maturity [2]. Fetal lung
maturity was indirectly assessed by ultrasonic fetal lung
morphology [3], fetal respiratory movement or fetal na-
sal respiratory flow imaging by Doppler ultrasound [4],
ripening of the placental image [5], Doppler blood flow
wave forms [6] or the intrauterine amniotic fluid choline
by magnetic resonance spectroscopy [7]. Noninvasive
direct assessment of fetal lung maturity was studied by
the ultrasonic fetal lung frequency component [8], B-
mode image texture [9] and special mean gray level [10],
where the ultrasonic methods should rely on a special
computer system or the mean gray level was so unstable
to the device gain and the depth of the subjects th at every
measurement needed test piece calibration. Ultrasono-
graphy has contributed by the use of chest circumference
and area [11] or by comparison with other fetal measure-
ments [12]. Attempts have also been made to correlate
the ultrasonic appearances of the placenta with fetal lung
maturity. In all of these studies, however, the sensitivity
and positive predictive value were poor, although the
non-invasive nature of this approach and rapidity of eva-
luation were attractive [13]. Estimates of direct fetal lung
volume have been made using 3-D ultrasound [14], but
these methods may be affected by liquor volume and do
not provide any additional physiological information
relating to potential function. In an attempt to establish
further non-invasive method for evaluation of fetal lung
maturity, the present study was designed to evaluate the
validity of measuring fetal thalamic echogenicity by ul-
trasound as a marker of fetal lung maturity.
2.1. Patients and Study Design
The present prospective longitudinal study involved 142
*Corresponding a uthor.
F. A. Rasheed et al. / Open Journal of Obstetrics and Gynecology 2 (2012) 270-275 271
pregnant women (age 31.0 ± 5.2 years) from 36 to 42
weeks of gestation (38.8 ± 2.6 weeks) who were admit-
ted for elective cesarean section for many indications
(Table 1) in Al-Elwiya Maternity Teaching Hospital/
Baghdad during the period from April 2010 to March
2011; after being fully familiarized with study protocol
and techniques; the protocol was in compliance with the
principles of the 1996 amendment the Declaration of
Helsinki, and the study was approved by both the Minis-
try of Health ethical committee and institutional review
board of Al-Kindy College of Medicine; the protocol
was compatible with the safety guidelines published by
the National Radiological Protection Board [15] and in-
formed written consent was obtained from each woman
prior to evaluation.
The inclusion criteria include women with single vi-
able pregnancy, uncomplicated pregnancy (hypertension
or diabetes), normal amount of liquor approved by ultra-
sound and Rh positive mothers. All included women
were examined by linear ultrasound with convex trans-
ducer frequency of 3.5 MHz (Braun, UK) at the Radio-
logy Department at the same day of their elective cesar-
ean section. During ultrasound examination we look for
the biparietal diameter (transthalamic plane) which was
measured in millimeters, and the state of echogenicity of
the thalamus was recorded as echogenic or echolucent in
comparison with the brain tissue between the thalamus
and the parietal bone which is echogenic through out
pregnancy; if the echogenicity of the thalamus appears
like brain tissue, it is considered echogenic, while if it
appears without echoes inside the thalamus it is echolu-
cent. The amniotic fluid particles (vernix) and the pla-
cental changes were also measured as a part of fetal
wellbeing assessment. All cases with complicated preg-
nancy, multiple pregnancy and pregnancy with known
fetal malformations, or those with oligohydramnios or
polyhydramnios were excluded.
2.2. Statistical Analysis
Statistical analysis was performed using the Statistical
Package for Social Sciences version 17.0 (SPSS Inc.,
Table 1. Indications of elective cesarean section.
Previous 1CS 38%
Previous 2 CS and more 23%
Primigravida 20%
Malpresentation 13%
For tubal ligation 3%
Postdate 3%
Chicago, IL, USA). The results of the study were ana-
lyzed statistically using descriptive statistics to describe
the observed frequencies with their percentages (Cross
tabulations). The validity of the US indicators compared
with fetal lung maturity were analyzed fo r validity of the
screening test through calculating sensitivity and speci-
ficity; the sensitivity is de fined as the probability of test-
ing positive if the disease is truly present and is calcu-
lated by: Sensitivity = (True positive by the test)/(True
positive + false negative) × 100%, while specificity is
defined as the probability of screening negative if the
disease is truly absent and is calculated by: Specificity =
(True negative by the test)/(True negative + false positive)
× 100% [16].
The changes in thalamic echogenicity in different gesta-
tional stages are demonstrated in Figures 1-4, which
represent the outcome in 64 cases (45.1%) of the evaluated
Figure 1. Ultrasonograph shows echolucent fetal thalamus (T)
at 36 weeks of gestation (white arrows).
Figure 2. Ultrasonograph shows echolucent fetal thalamus (T)
at 36 weeks of gestation (white arrows).
Copyright © 2012 SciRes. OPEN ACCESS
F. A. Rasheed et al. / Open Journal of Obstetrics and Gynecology 2 (2012) 270-275
Copyright © 2012 SciRes.
Table 2 showed that for the 4 ultrasonic criteria meas-
ured during the present study, the specificity and the
positive predictive values are higher for the thalamic
density. However, the pr esence of vernix in the amniotic
fluid showed more sensitivity (86.66 %) versus 63.33% in
the thalamic density. Meanwhile, Table 3 showed that
the four ultrasound parameters of lung maturity were in-
creased with gestational age, and the presence of vernix
in the amniotic fluid shows the highest and more predic-
tive percent compared to the others (73.9%), while the
feature of echogenic thalamus demonstrate relatively
lowest value (45.1%), though it appears comparable to
that of grade 2 and 3 placental calcification feature.
Concerning the neonatal outcome of the present study,
Table 4 showed that neonatal morbidity mostly occu rs at
early stages of the gestational age (less than 39 weeks)
and represents 35/52 of total admission to the Neonatal
Intensive Care Unit (NICU), and the admission was
19/52 for less than 24 hour and 5/52 for more than 48
hours. The present study did not report any neonatal
death up to discharge of ne w bo r n babi es fr o m the NICU.
Figure 3. Ultrasonograph shows echogenic thalamus (T) at 38
weeks of gestation (white arrows).
It would be convenient to predict fetal lung immaturity
before an elective birth noninvasively to allow thera-
peutic protection against possible respiratory distress
syndrome (RDS) in the neonate, or in some cases, to esti-
mate the effect of adrenal steroid treatment of a preterm
fetus by repeated tests that can be freely performed by
noninvasive techniques. Prenatal diagnosis permits deli-
very by planned caesarean section sufficiently early to
Figure 4. Ultrasonograph shows echogenic thalamus (T) at 38
weeks + 3 days of gestation (white arrows).
Table 2. Comparison between the sensitivity and the specificity of the four ultrasound parameters in our study as a sign of fetal lung
Ultrasound parameters Sensitivity (%)Specificity (%) Positive predictive value (%) Negative predictive value (%)
Echogenic thalamus 63.33 86.53 89.6 57.69
Placental calcification grade 2 and 3 51.11 71.15 75.40 45.67
Biparietal diameter above 9.2 cm 62.22 42.30 65.11 39.28
Presence of amnio t ic fl u id ve rnix 86.66 48.07 74.28 67.56
Table 3. The predicted percent US outcome in the four ultrasound parameters of fetal lung maturity ranked according to gestational
Gestational age
Ultrasound parameters 36 week 37 week 38 week 39 week 40 week 41 - 42 week Total
Number of cases 12 31 45 38 13 3 142
Echogenic thalamus 2 (16.7) 14 (45.2%)14 (31.1%)21 (55.3%)10 (76.9%) 3 (100%) 64 (45.1%)
Placental calcification grade 2 and 3 3 (25% ) 13 (41.4%)16 (35.6%)19 (50%) 8 (61.5%) 2 (66.7%) 61 (43%)
Biparietal diameter above 9.2 cm 1 (8.3%) 8 (25.8%)30 (66.7%)33 (86.8%)11 (84.6%) 3 (100%) 86 (60.6%)
Presence of amniotic fluid vernix 4 (33.3%) 22 (71%) 31 (68.9%)34 (89.5%)11 (84.6%) 3 (100%) 105 (73.9%)
F. A. Rasheed et al. / Open Journal of Obstetrics and Gynecology 2 (2012) 270-275 273
Table 4. Neonatal outcome according to evaluation of thalamic echogenicity.
Gestational age
Neonatal outcome 36 week37 week38 week39 week40 week 41 - 42 weekTotal
Number of cases 12 31 45 38 13 3 142
Good neonatal outcome
(not needed to be admitted to the NICU) 5 (41.6%)18 (58.1%)30 (66.7%)24 (63.2%)10 (76.9%) 3 (100%) 90 (63.4%)
Total admission to the NICU 7 (58.3%)13 (41.9%)15 (33.3%)14 (36.8%)3 (23.1%) 0 52 (36.6%)
Admission to the NICU less than 24 hrs 1 (8.3%)8 (25.8%)10 (22.2%)9 (23.7%)3 (23.1%) 0 31 (21.8%)
Admission to the NI CU from 24 to 48 hrs 4 (33.3%)4 (12.9%)3 (6.7%)5 (13.2%)0 0 16 (1 1.3%)
Admission to the NICU more than 48 hrs 2 (16.7%)1 (3.2%)2 (4.4%)0 0 0 5 (3.5%)
TTN or RDS 3 (25%) 10 (32.3%)13 (28.9%)14 (36.8%)3 (23.1%) 0 43 (30.3%)
RDS 4 (33.3%)3 (9.6%)2 (4.4%)0 0 0 9 (6.3%)
Treated hypoglycemia 1 (8.3%)1 (3.2%)2 (4.4%)0 0 0 4 (2.8%)
Neonatal mortality 0 0 0 0 0 0 0
NICU: Neonatal Intensive Car e Unit; TTN: Transient Tachypnea of the Newborn; RDS: Respir atory Distress Syndrome.
avoid the possible complications. A review of 155 cases
found that prenatal diagnosis results in a 95% reduction
in late fetal and neonatal mortality [17]. Such observa-
tions have inspired several clinical groups [17-20] and
parents to recommend routine identification of umbi-
lical cord insertion at 20 weeks of gestation and tar-
geted screening for vasa praevia in women identified as
at high risk for the condition. Many studies of ultra-
sound prediction of fetal lung maturity were used to
compare ultra-sound parameters with tests of amnio-
centesis to assess that sign with lung maturity [10].
Amnio centesis is not ava ilable in our prac tice, so in the
present study we compare the ultrasound parameters
with the neonatal outcomes (APGAR score, the need
for admission to the NICU and any sign of respiratory
distress). From clinical practice it has been noticed that
thalamic density increased with gestational age, so the
present study; for the best of our knowledge, was car-
ried out to assess this sign and try to adopt it as an
indicator for lung maturity; this subject was presented
for the first time and not previously reported elsewhere.
In the present study, through non-invasive technique,
we try to evaluate fetal thalamic echogenicity by ultra-
sound as a new indicator for lung maturity and compare
it with other previously known signs of fetal lung
maturity such as biparietal diameter, amniotic fluid
vernix and placental changes. The data showed that the
thalamus is echogenic in 64 cases (45%) and echolucent
in 78 cases (55%) and the echogenicity increases with
the increase in the gestational age; this result seems
comparable to a previously reported data that correlate
thalamic echogenicity with gestational age by the same
author [21]. The presence of echogenic thalamus as a
sign of fetal lung maturity by ultrasound was found to
be of high specificity in detecting fetal lung maturity
and demonstrates high positive predictive value com-
pared to other ultrasound parameters utilized in the
present study; however, the sensitivity and negative
predic tive value w ere reported to be lower compared to
the signs of vernix in the amniotic fluid. Although the
utilized technique is simple and can be easily performed
in all obstetrics units, the echo reflection is not meas-
urable and depends on the experience of the examiner,
which represents a major difficulty in interpretation of
It has been reported that both grade II and III placenta
predicted fetal lung maturity in 100% of cases [22],
suggesting that placental grading could replace estima-
tion of the L/S ratio and thereby avoid amniocentesis and
its complications. However, subsequent workers in this
field have cast doubt on the reliability of placental grad-
ing as a predictor of fetal lung maturity [23,24], and the
subject has became controversial for a many reasons
including presence of complications like hypertension,
diabetes mellitus or Rh iso-immune disease. Accordingly,
the search for novel signs and markers for prediction of
lung maturity became an interested discipline in the
obstetrics field. The present study confirmed the previ-
ously reported data that grades II and III placentas were
highly associated with fetal lung maturity [25]. Mean-
while, the finding of fetal lung maturation in 83.3% of
infants in grade III group justifies using this group to
indicate fetal lung maturity before repeat caesarean
section in woman with reasonable certainty to reach 38
weeks of gestation and has no complicating diseases.
However, because only 18% of our patients had a grade
Copyright © 2012 SciRes. OPEN ACCESS
F. A. Rasheed et al. / Open Journal of Obstetrics and Gynecology 2 (2012) 270-275
III placenta, those with grade II placenta satisfying the
provisos mentioned above should be managed in the
same way as those in grade III on the basis of our find-
ings, and even with this group 75.4% of fetuses had
achieved lung maturity, such finding seems compatible
with that reported previously [22]. Hadlock et al. (1985)
utilized amniocentesis for determination of fetal lung
maturity and ultrasonographic (US) evaluation of the
biparietal diameter (BPD) and placental grade were per-
formed simultaneously and concluded that the ability of
the sonograph ic parameters to predict fetal lung maturity
was closely related to menstrual age and the best use of
US for predicting fetal lung maturity is in establishing
menstrual age early in pregnancy [26]; the results ob-
tained in the present study support the previously men-
tioned idea. Concerning evaluation of the presence of
FFPs in the amniotic fluid, Gross et al. (1985) correlate
this ultrasound finding with fetal lung maturity and
suggest that presence of FFPs on real-time ultrasound
could be used to confirm fetal lung maturity [27]. The
data presented in this study support the previously men-
tioned one an d more than on e u ltr asound mar k er s may be
better correlated for prediction of fetal lung maturity.
Moreover, the present study demonstrates that a BPD
greater than or equal to 92 mm predicted 56 of 90
(62.22%) cases with mature lung, while the presence of
FFPs predicted 78 of 90 (86.66%); when utilized toge-
ther, a BPD equal to or greater than 92mm and/or the
presence of FFPs predicted 83 of 90 (92.22%) of cases
with mature fetal lung, and such finding complies with
data reported by others, where BPD greater than or equal
to 92 mm and the presence of free-floating particles are
independent, and considered as complimentary predic-
tors of fetal lung maturity [28]. Subjective approach
during measurement of echogenicity and lack of a me-
thod to measure the gain of echoes are the limitations of
the present study, in hope th at we can overco me in future
studies. In conclusion, evaluation of echogenic thalamus
by ultrasound at the lev el of the BPD is of value, and can
be considered as a new marker of fetal lung maturity;
however, further studies are required to strengthen such
The authors would like to thank University of Baghdad for support;
also they gratefully acknowledge the ultrasonography staff of Al-
Elwiya Maternity Teaching Hospital for technical assistance.
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