Revista Română de Anatomie funcțională și clinică, macro- și microscopică și de AntropologieVol. XIV Nr. 2 2015 CLINICAL ANATOMY [625431]

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Revista Română de Anatomie funcțională și clinică, macro- și microscopică și de AntropologieVol. XIV – Nr. 2 – 2015 CLINICAL ANATOMY
ULTRASONOGRAPHIC EMBRIOLOGY . NORMAL PREGNANCY .
FIRST TRIMESTER
Angela Ilie, Mihaela A. Banu, R. Cergan, Ioana R. Rusu
University of Medicine and Pharmacy “Carol Davila” Bucharest
2nd Preclinical Department
Morphological Sciences
ULTRASONOGRAPHIC EMBRIOLOGY . NORMAL PREGNANCY . FIRST TRIMESTER (Ab-
stract): By means of ultrasonography one can visualise and monitor elements of embryo develope –
ment from a very early gestational age (4 weeks and 6 days- the moment when the gestational sack
can be visualised) all the way to the term of delivery. The first trimester can be split in three
periods: preembrionary, embrionary and fetal. During the early stages one seeks to fulfill the
following goals:- diagnosing pregnancy, locating the pregnancy and looking into its viability, so
that at a later date (weeks 1 1-14) one can make a detailed analysis of the anatomy of the fetus.One
can make a connection between the elements of embriological developement and the imagistic
expression (by means of ultrasonography) of the moment each element appears. Keywords :
ULTRASONOGRAPHY , PREEMBRYONIC, EMBRYONIC, FETAL, CONNECTION
In ultrasonography the term gestational age
(GA) is used. GA means the time from the last
known menstruation, time which can be pre –
cisely determined. For a 28-day cycle, ovulation
takes place in the fourteenth day (D14) and thus
frome the moment of fecundation one can measure
the conceptional age. Gestational age, measured
in days since amenorrhea, will be conceptional
age plus 14 days, and as such, one will analyse
weeks 1-13+6 days in order to monitor the status
of the pregnancy during the first trimester.
As far as embryological developement goes,
one will monitor the following: week 1 (nida –
tion), week 2 (bilaminar disc), weeks 3-8 (em –
bryonic period), week 9-delivery term (fetal
period). Trimester I= W1- W12
By means of ultrasonography, one is to mon –
itor the following: preembryonic period – from
the moment of fecundation (D14) to week 5
(D35), embryonic period (weeks 5-10), fetal
period (from week 10 to term).Trimester I=
W1-W14
PURPOSE OF STUDY
• Connection between the elements of em-
bryological developement and the imagistic expression (by means of ultrasonography) of
the moment each element appears.
• Diagnosing pregnancy (visualisation of the
gestational sack and its position, the number
of embryos, signs of embryonic viability).
• Pinpointing the location of the pregnancy
(intrauterine or extrauterine).
• Determining the gestational age (biometrical
measurements: gestational sack diameter
-GSD, crown-rump length -CRL, transverse
abdominal diameter -TAD, head circumfer –
ence -HC, abdominal circumference -AC).
• Monitoring the evolution of the pregnancy.
MATERIAL AND METHODS
The following project is based on the moni –
toring by means of ultrasonography of a number
of 30 pregnant women during their first trimes –
ter of pregancy. The pregnancies are of differ –
ent ages and examinations I have monitored the
connection between the age of pregnancy, the
embryological developement elements and their
ecographical image. The technique utilised is
transvaginal and/or transabdominal examina –
tion.
1) Preembryonic period (D14-D35= W5)

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Angela Ilie et al.Up until W4-W5 there are no clear ultra –
sonographical signs that can diagnose preg –
nancy. The signs are indirect, by noticing the
following: growth of the uterus and its globu –
lar shape, decidualization of the endometrium
(14-24mm) – fig.1 (at a later date pregnancy
was confirmed and she is now participating in
this study as a subject).One can add to these
signs the presence of a corpus luteum gravidi –
tatis (fig. 2) on one of the ovaries (up until a
clear pregnancy diagnosis is given, one can
suspect an ovary cyst but as far as the corpus
luteum is concerned, it is usually located at the
center of the ovary). The corpus luteum pro –
duces progesterone and it keeps doing so until
the placenta is formed.
During W4-W5 one can diagnose pregnancy
by identifying the anecogenous gestational sack
(GSD) ,with a diameter of 0,8-1cm (fig. 3, fig.
4) surrounded by an ecogenous ring– by means
of transvaginal examination (W4-W5, diameter of 1-2mm) and by means of transabdominal
examination (>W5, diameter >2mm).
The position of the gestational sack represents
the place of implantation and partially occupies
the uterine cavity, the rest of it being padded
by decidualized endometrium. After 5 weeks
of amenorrhea, GSD has a hiperecogenous ring
that sets it apart from the surrounding tissue,
ring made out of the trophoblast, and it resem –
bles the decidualized endometrium (fig. 3,4).
2) Embryonic period (W5-W10)
After W5 the gestational sack grows and it
will fully occupy the uterine cavity. If the sack
is not round further measurements are made
(transverse diameter, longitudinal diameter,
antero-posterior diameter).
Around week 5-6, the embryonic echo is
hard to visualise and it is located next to the
secondary umbilical vesicle (UV) = vitelline
vesicle (VV) = Y olk sack (YS) – fig. 6. The
vitelline vesicle is a round, anecogenous forma –
Fig. 1. Decidualization of the endometrium
Fig. 2. Corpus luteum graviditatis
Fig. 3‑4 . The anecogenous gestational sack (GSD), surrounded by an ecogenous ring

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Ultrasonographic Embriology. Normal pregnancy. First Trimestertion surrounded by an ecogenous ring, with a
diameter of 3-5 mm, originally situated at the
center, outside the amnios. The YS is visible
up until the twelfth week of amenorrhea .
The embryo is clearly visible at the sixth week
of amenorrhea, the cardiovasculary system being
the first to start operating (embryonic heart bpm,
HR, FHR).
For subject IA, with a pregnancy of an ul –
trasonographically-determined gestational age
(GA- LMP) of 5 weeks. 6 days the following
were measured: CRL- 0,34cm, GSD- 1,55cm,
HR- 1 1 1bpm, YS 3,9mm.
Weeks 7-8. By means of ultrasonography,
one measures and visualises the following:
• The embryo and its active embryonic move-
ment (AME)
• CRL (fig.10)
• GSD (fig. 11)
• HR (130b/min during W7 si 160b/min dur-
ing W8, 180b/min during W8-W9)
• During W6-10 -from conception (W8-12
since last menstruation) the growth of the liver takes place, which determines the ap –
parition of the physiological hernia, the in –
testinal ansae lacking sufficient space in the
abdominal cavity and thus herniating in the
proximal area of the UC)- fig. 17
• UV positionned centrally
• membranes that sepparate the amniotic and
chorionic cavities (extraembryonic coelome).
Amniotic cavity + amniotic fluid
• The hiperecogenous contour of the gesta-
tional sack starts sketching the choriom fro –
dosum at the embryonic pole and the cho –
riom laeve at the abembryonic pole
Week 9-10. Ecography shows the following:
a) embryo on which one observes and meas –
ures the following:
• CRL- at 8weeks. 6 days it is approxi –
mately 20mm, at 9weeks. 6 days it is
approximately 30mm (fig. 13)
• The cephalic pole is highlighted and at
the end of W10 at head level one can see
the following: lateral ventricles with
choroid plexuse s, falx cerebri, the thala –
Fig. 5. W5D3, the embryo cannot be seen yet. Fig. 6. Vitelline vesicle seen at W5D3

316
Angela Ilie et al.mus. At th e back of the head one can see
a cystic formation that is the rhomben –
cephalon, the future ventricle IV (fig.16)
• The spine becomes visible
• In the abdominal area one visualises:
the liver which occupies most of the ab –
dominal cavity and the physiological her –
nia (fig. 17)
• Limb buds
• HR- 180b/min during W9, starts decreas –
ing afterwards
• Nuchal translucency= Nuchal fold (fig.
22)
•AME globale
b) GSD
c) UV which is pushed towards the periphery
(between amnios and chorion), and then gets
included in the future placenta (fig. 14).
d) From W9 onwards the chorion frodosum is
clearly differentiated and takes a granulous
aspect in W10 (fig. 15).
e) The membranes ind ividualising the amni -otic and chorionic cavities. By W10 the am –
nion (amniotic membrane) fuses with the
chorionic cavity and thus the amniotic cav –
ity is born.
3) Fetal period (W10- W14).
Weeks 10-12. Ecography shows:
a) The embryo on which one monitors:
• CRL (fig. 18)
• the cranium: osseous contour, lateral
ventricles, choroid plexuses (butterfly
appearance-fig. 27), falx cerebri, the
thalamus, nasal bone- fig.22 (its absence
is a risk of Down syndrome), orbits;
BPD (biparietal diameter), HC (head cir –
cumference)
• The heart – four chambers aspect, HR
140b/min (frequency was reduced by the
fetal vagal function)
• The spine
• Nuchal translucency (fig. 26)
• Limbs with three segments each; FL
(femur length) (fig. 25)
Fig. 7. CRL (5W 6D) Fig. 8. Hart rate (1 1 1bpm)
Fig. 9. Vitelline vesicle (UV)

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Ultrasonographic Embriology. Normal pregnancy. First Trimester
Fig. 10‑12. In the case of this subject the date of the last menstruation is unknown and as a result the
age of the pregnancy as well as the most likely date of birth will be based solely on ultrasonographic
measurements. (Fig. 10-12), Fig. 12 HR 182bpm
Fig. 13. CRL 8W 6 D Fig. 14. UV which is pushed towards the
periphery (between amnios and chorion)
Fig. 15. From W9 onwards the chorion frodosum
is clearly differentiated and takes a granulous
aspect in W10.

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Angela Ilie et al.
Fig. 16. CRL 9W 6 D Fig. 17. The umbilical physiological hernia
Fig. 18. CRL 1 1W5D Fig. 19. HR 160bpm (12W)
• The abdomen: the physiological hernia
disappeara (the intestinal ansae are now
back in the abdominal cavity), the liver,
the stomach, the kidneys and the urinary
bladder; DTA (transverse abdominal di –
ameter), CA (abdominal circumference)
• Quick and slow AMF
b) Placenta: Location, maturity degree, thick –
ness
c) Umbilical cord (can be seen even in week 9
with high resolution ecography)d) amniotic fluid
Ultrasonographically, trimester I ends with
W14 (GA-LMP), and between W12-14 the same
parameters are monitored as in W12, with the
difference that CRL is no longer so precise in
calculating the gestational age due to the fact
that the fetus starts curving.
By ecographical means one can measure the
length of the cervix (fig. 28) and also takes into
account the internal cervical orifice and the chance
of abortion should it prove to be shortened.

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Ultrasonographic Embriology. Normal pregnancy. First Trimester
Fig. 20. CRL 12W Fig. 21. Nuchal fold 2,3mm
Fig. 22. Nasal bone Fig. 23. HR 160bpm
Fig. 24. CRL 12W 4D Fig. 25. FL 12S 5Z
CONCLUSIONS
1) Out of the 30 examinated pregnant women
(30 embryos) resulted a connection between
the embryonic developement elements and
the imagistic expression of the moment each element appeared.
2) The normal evolution of the pregnancy is
monitored by means of ultrasonography.
3) The determination of the gestational age and
the most likely date of birth as accurately as

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Angela Ilie et al.
Fig. 26. Nuchal fold 2,1mm Fig. 27. BPD 13W3 D
Fig. 28. The length of the cervix 3,6 cm (12W 6D)
possible, based on ecographic measurements
(even if the date of the last menstruation is
unknown, for those with irregular cycles)
4) The obtained data can be used to calculate
the risk of apparition of several aneuploidies (nasal bone, nuchal translucency). The mea-
surements are part of the procedure for sev –
eral first trimester tests (the double test is
performed between 1 1-13 weeks+ 6 days
and uses the NT).
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