first trimister ultrasound and overview of obstetrics imaging

1. Overview of Obstetric Imaging and The
First Trimester
Presented By:
Dr. Bharat Jain
VMKVMC

2. Introduction

Use of ultrasound Scans in pregnancy
introduced in late 1950s

Provision of good information about the foetus
and its environment

Determining early intervention or conservative
management

Safe, non-invasive, accurate and cost effective
investigation in foetus

Important role in care of pregnant woman

3. Indication for first-trimester ultrasound

To confirm the presence of an intrauterine pregnancy.

To evaluate a suspected ectopic pregnancy.

To define the cause of vaginal bleeding.

To evaluate pelvic pain.

To estimate gestational (menstrual) age.

To diagnose or evaluate multiple gestations.

To confirm cardiac activity.

4. 
As an adjunct to chorionic villus sampling, embryo transfer, and
localization, and removal of an intrauterine device.

To assess for certain fetal anomalies, such as anencephaly, in
high-risk patients.

To evaluate maternal pelvic masses or uterine abnormalities.

To measure nuchal translucency when part of a screening
program for fetal aneuploidy.

To evaluate a suspected hydatidiform mole.

5. 
Estimation of gestational (menstrual) age

Evaluation of fetal growth

Vaginal bleeding

Abdominal or pelvic pain

Cervical insufficiency

Determination of fetal presentation

Suspected multiple gestation

Adjunct to amniocentesis or other procedure

Significant discrepancy between uterine size and clinical dates

Pelvic mass

Suspected hydatidiform mole

Adjunct to cervical cerclage placement

Suspected ectopic pregnancy

Suspected fetal death

Suspected uterine abnormality
Indications for second and third trimester ultrasound

6. 
Evaluation of fetal well-being

Suspected amniotic fluid abnormalities

Suspected placental abruption

Adjunct to external cephalic version

Premature rupture of membranes and/or premature labor

Abnormal biochemical markers

Follow-up evaluation of a fetal anomaly

Follow-up evaluation of placental location for suspected placenta previa

History of previous congenital anomaly

Evaluation of fetal condition in late registrants for prenatal care

To assess for findings that may increase the risk for aneuploidy
screening for fetal anomalies

7. GUIDELINES FOR
FIRST-TRIMESTER ULTRASOUND

Gestational sac

Location of pregnancy: intrauterine vs extrauterine

Gestational age (as appropriate)

Mean sac diameter

Embryonic pole length

Crown-rump length

Yolk sac or embryo/fetus

Cardiac activity on M-mode ultrasound

Fetal number (amnionicity/chorionicity)

Maternal anatomy: uterus and adnexa

8. Normal first-trimester ultrasound images:
pregnancy location and adnexa.
A, Transabdominal sagittal sonogram shows an
intrauterine gestational sac.
B, Transverse image to the left of uterus shows
normal appearance for the ovary(arrow).
C, Transvaginal color Doppler image shows
normal hypervascular rim around corpus luteum.
A B
C

9. Normal first-trimester ultrasound images: mean sac diameter. Transvaginal
sagittal image shows sagittal measurement of sac diameter (calipers).
Measurements in three orthogonal planes are averaged to calculate the mean
sac diameter. Note yolk sac within the gestational sac.

10. First-trimester ultrasound images: embryo and fetus. A, Normal embryo at 6.5 weeks’ gestation. Note
embryonic pole (calipers) adjacent to yolk sac. B, Normal embryo at 8 weeks’ gestation. Note embryo (calipers) and adjacent yolk sac
(arrow). C, M-mode ultrasound from same embryo as in B. Note normal heart rate of 160 beats/min. D, Normal embryo at 9 weeks’
gestational age. Note embryo within amnion (arrow) and umbilical cord (arrowhead). E, Just lateral to image in D, note yolk sac (arrow-
head) is located outside the amnion (arrow). F, Sagittal ultrasound at 10.5 weeks’ gestation. G, Sagittal ultrasound at 11.5 weeks’ gestation.
H, Coronal view of face at 13 weeks’ gestation. I, Sagittal ultrasound of nuchal translucency (calipers) at 13 weeks’ gestation.
A B C
D E F
G H I

11. Multiple gestations. Be sure to examine the entire gestational sac to identify multiple gestations. A, Transabdominal image of
diamniotic dichorionic twins. Note the thick, dividing membrane. B, Transvaginal image of diamniotic monochorionic twins at 8
weeks’ gestational age (calipers denote crown rump length) with two thin membranes (arrows, amnion) still close to
embryonic poles.
Anencephaly. A, Sagittal ultrasound at 10 weeks’ gestation. B, Sagittal ultrasound in a different fetus at 12 weeks’ gestation.
Note the orbits (arrow) with absent ossified cranium above this level with angiomatous stroma.
A
B
B
A B

12. Omphalocele at 11 weeks’ gestational age. Sagittal view
of fetus (calipers) shows a large, abdominal wall defect
(arrow).

13. GENERAL SURVEY

Cardiac activity: document with M-mode

Presentation: cephalic, breech, transverse, variable

Fetal number: for multiples, amnionicity/
chorionicity, concordance with size, amniotic fluid

Maternal anatomy: uterus, adnexa, and cervix

Gestational age and fetal weight assessment
Biparietal diameter
Head circumference
Abdominal circumference
Femur length

Amniotic fluid
Estimate as normal
If abnormal, qualify if high or low

Placenta: position
GUIDELINES FOR SECOND-
AND THIRD-TRIMESTER ULTRASOUND

14. FETAL ANATOMIC SURVEYFETAL ANATOMIC SURVEY
Head, Face, and NeckHead, Face, and Neck
Cerebellum
Choroid plexus
Cisterna magna
Lateral cerebral ventricles
Midline falx
Cavum septi pellucidi
Upper lip
ChestChest
Four-chamber view
Outflow tracts “if technically feasible”
Abdomen
Stomach (presence, size, and situs)
Kidneys, bladder
Umbilical cord insertion site into fetal abdomen
Umbilical cord vessel number

15. Spine
Cervical, thoracic, lumbar, and sacral
Extremities
Legs and arms: presence or absence
Gender (Sex)
Medically indicated in low-risk pregnancies only for
evaluation of multiple gestations

16. Overview of uterus, cervix, and fetal position. A, Sagittal sonogram of uterus shows a normal-appearing cervix (C) and
an anterior placenta (P), with the placental tip far away from the internal cervical os; B, bladder. B, Transverse
sonogram of posterior placenta (P). C, Transabdominal image of normal-appearing cervix (arrow on internal os). Note
bladder (B) and fetal head (H). With the head as the presenting part, the fetus is in cephalic position. D, Transvaginal
sonogram of normal-appearing cervix (calipers).
A B
C D

17. Determination of situs. A, Scan plane, and B, transverse scan diagram. With fetus in cephalic
position and spine on the maternal right side, the left-sided stomach is “up” on the side closest to
the transducer. C, Scan plane, and D, with the fetus in breech position and spine on the maternal
right side, the left-sided stomach is “down” on the side farthest away from the transducer.

18. ADDITIONAL VIEWS FOR TARGETED
FETAL SONOGRAMS

Corpus callosum

Cerebellar vermis

Outflow tracts

Orbits

Extremities, including hands and feet

Profile/chin

Nuchal fold (at appropriate gestational age)

Individual long-bone measurements

Hands and feet

19. Second-trimester biometry. A, Biparietal diameter. Note the level of this ultrasound image at the thalamus and third
ventricle. The calipers are placed from the outer skull in the near field to the inner skull in the far field. B, Head
circumference. Note how circumference is measured around the outside of the skull. Arrow depicts cavum of the septum
pellucidum. C, Abdominal circumference. Note the curve of the portal vein and stomach on this transverse image, with
circumference drawn around the outside of the skin. D, Femur length. Note that the “upside” femur should be measured,
with the shaft of the bone as near to perpendicular to the scan plane as possible, excluding the distal femoral epiphysis.
A B
C D

20. Routine sonographic views of fetal head. In addition to the biparietal diameter and head circumference, required views
of the head include images of the cerebral ventricles, cerebellum, cavum of the septum pellucidum, and midline falx.
Additional views that can be obtained are angled views to demonstrate both sides of the choroid plexus, and views
through the anterior fontanelle or midline sutures to demonstrate the corpus callosum. A, Axial image shows cerebral
ventricles filled with choroid plexus. B, Angled axial view shows both ventricles with choroid plexus. C, Axial image
shows cerebellum (arrow) and cavum of the septum pellucidum (arrowhead). D, Transvaginal sagittal view of the
corpus callosum (arrows).
A B
C D

21. Views of fetal face. Required view of the face is of the nose and lips. Additional views include orbits and profile. A,
Coronal view of nose and lips. B, Coronal view of orbits. C, Sagittal view of facial profile. D, 3-D image of fetal face.
A B
C D

22. Views of fetal heart and outflow tracts. Required views
include demonstration of normal situs, with heart and
stomach on left side, four-chamber view of the heart,
documentation of normal heart rate, and outflow tracts “if
possible”. A, Axial image shows normal four-chamber view
of fetal heart. Note the normal axis of the heart, at about
60 degrees from midline. B, M-mode ultrasound. Note
normal heart rate (146 beats/min). C, Angled view shows
left ventricular outflow tract (arrow) with heart and
stomach(s) on the same side of the fetus. D and E, Right
ventricular outflow tract in oblique axial (D) and oblique
sagittal (E) views with ductus arteriosus (arrow) extending
posteriorly to aorta.
A B
C D
E

23. Views of fetal abdomen and pelvis. Note normal stomach
documented on abdominal circumference. Other required views are
cord insertion, kidneys, and bladder. Additional views document the
diaphragm and fetal gender. A, Cord insertion site in the anterior
abdominal wall. B and C, Transverse views of kidneys at 18 and 28
weeks’ gestation. A small amount of central renal pelvic dilation (2
mm in this fetus) is a normal finding. D, Transverse image of
bladder. Note umbilical arteries on either side of bladder. E, Sagittal
view shows liver, diaphragm (arrow), and lungs. Note how the liver
is of lower echogenicity than the lungs. F, Male genitalia. G, Female
genitalia.
A
B C
D E F
G

24. Views of fetal spine. Note transverse image of thoracic
spine on four-chamber view and transverse image of
lumbar spine between the kidneys . A, Transverse
image of cervical spine. B, Transverse view of
lumbosacral spine. Note how the posterior elements
point towards each other and the skin covers the distal
spine. C, Oblique sagittal image of cervical and
thoracic spine. D, Oblique sagittal view of entire spine.
E, Sagittal view focused on the distal spine. Note how
the spinal canal narrows and has a gentle upturn
distally.
A B
D
E
C

25. View of fetal extremities. Required
views include documentation of all four
extremities. Additional views include
measurements of all the long bones
and demonstration of the fingers and
toes. A and B, Lower extremities. C, D,
and E, Upper extremities. F, Hand.
Note four fingers with thumb partially
out of the field of view. G, Foot. H, 3-D
view of upper extremity.
A B
C
D
E F
G H

26. Views of umbilical cord. Required views include cord insertion site into the anterior abdominal wall (see Fig. A) and
documentation of number of vessels in the umbilical cord. Additional views include cord insertion site into the placenta
and Doppler examination of the cord. A, Transverse image of three-vessel umbilical cord. Note two arteries (arrows) that
are smaller than the single vein (arrowhead). B, Color Doppler longitudinal image of three-vessel cord. C, Cord insertion
site (arrow) into the placenta. D, Spectral Doppler image documents normal umbilical arterial systolic/diastolic ratio in
third-trimester fetus.
A B
C
D

27. BENEFITS OF ROUTINE SECOND- TRIMESTER
ULTRASOUND SCREENING

More accurate gestational age

Detection of major malformations before birth

Earlier detection of multiple pregnancy

Fewer low-birth-weight singleton births

Lower incidence of induction for postterm pregnancy
• Early detection of placenta previa
• Reassurance of a normal pregnancy

Identification of twin / multiple pregnancies

Fetal malformation: Diagnostic accuracy

3D&4D ultrasound

28. MRI in Pregnancy

When additional information regarding fetal anatomy
or pathology is needed, fast MRI increasingly being
used.

There is no biological risk from MRI

MRI provides excellent soft tissue contrast, multiple
planes for reconstruction and large field of view.

29. Normal fetal MRI: representative T2-weighted images. A, Sagittal view of fetal head with fetal body in coronal plane. B,
Sagittal view of fetal head. Note normal appearance of corpus callosum and soft palate, with fluid outlining the soft palate
above the tongue. C, Coronal view of the brain, chest, and abdomen. Note normal appearance to the lungs, diaphragm,
stomach, and kidneys. D, Axial view of brain with normal-appearing lateral ventricles. E, Oblique axial view of brain shows
normal cerebellar hemispheres and vermis. F, Axial view at level of globes. Note the dark lens in each globe. G, Axial
view at level of palate. Note that majority of the alveolar tooth-bearing ridge is well depicted. H, Axial view at level of
stomach and gallbladder. Note spinal cord outlined by fluid in thecal sac. I, Axial view at level of bladder.
A
B C
D E F
G
H I

30. GOALS OF FIRST TRIMESTER
SONOGRAPHY

Visualization and localization of the gestational sac

Early identification of embryonic demise and other forms
nonviable gestation

In multifetal pregnancies, number of embroyos and the
chorionicity-amnionicity

First trimester focuss on nuchal translucncy screening
combined with maternal age and maternal serum to
determine risk of chromozomal abnormalities

31. Schematic drawing of interrelationships among the hypothalamus, pituitary gland, ovaries, and endometrial lining. FSH,
Follicle-stimulating hormone; LH, luteinizing hormone. (From Moore KL, Persaud TVN, editors. The developing human:
clinically oriented embryology. 6th ed. Philadelphia, 1998, Saunders.)
Maternal physiology
and Embryology

32. Diagram of ovarian cycle, fertilization, and human development to the blastocyst stage.
(From Moore KL, Persaud TVN, editors. The developing human: clinically oriented embryology. 6th ed. Philadelphia,
1998, Saunders.)

33. Implantation of the blastocyst into endometrium. Entire conceptus is approximately 0.1 mm at this stage. A, Partially
implanted blastocyst at approximately 22 days. B, Almost completely implanted blastocyst at about 23 days.

34. Formation of secondary yolk sac. A, Approximately 26 days: formation of cavities within extraembryonic
mesoderm. These cavities will enlarge to form extraembryonic coelom. B, About 27 days, and C, 28 days: formation of
secondary yolksac with extrusion of primary yolk sac. Extraembryonic coelom will become chorionic cavity.

35. Gestational Sac

First reliable evidence of an IUP is visualsation of the
gestational sac within the thicken decidua (Yeh et al.)

Gestational sac should be eccentrically located within the
endometrium and should abut the endometrial-canal

Demonstrate an early IUP as a small intra decidual sac
between 4.5 and 5 weeks gestational age using TVS

The threshold level identifies the ealiest one can expect
to see a sac (4 weeks, 3 days), and the discriminatory
level identifies when one should always see the sac (5
weeks, 2 days)

Double decidual sign is based on visualisation of the
gestational sac as an ecogenic ring formed by the
decidua capsularis and chorion, forming 2 ecogenic rings

36. Intradecidual sac sign. A, Sagittal scan at 4 weeks, 4 days shows implantation site as a 2-mm focal thickening
of posterior endometrium (arrow). The chorionic fluid in the sac is just barely visible. The mass slightly
displaces the endometrial stripe and has a slightly echogenic rim. B, Color Doppler image shows prominent
terminal portion of a spiral artery (arrow) extending up to the sac.
A B

37. Intradecidual sac sign. A, Transabdominal scan at 32 days. The small sac is not visualized in this scan. B and C,
Transvaginal scans the same day showing the echogenic ring of the sac (black arrow) implanted just below the
endometrial interface ( arrowhead). D, Color Doppler flow of a feeding spiral artery adjacent to the sac with low-velocity
flow of 10 cm/sec.
A B
D
C

38. Double-decidual sign.
Diagram of anatomic basis showing three
layers of decidua and endometrial cavity.
Decidual layers. Sagittal
transvaginal sonogram at 7 weeks
shows the gestational sac
(arrowhead) and the maternal
decidua (arrow) as separate
echogenic bands.

39. Subchorionic hemorrhage. A, Transab-
dominal scan at 10 weeks. The sac and embryo
are seen as well as a fluid collection (arrow)
behind the chorion, a subchorionic hemorrhage.
(arrow) B, Transvaginal sagittal and 3-D scans
show the fluid collections (arrows); e, embryo; c,
chorion.
A
B

40. Echogenicity of fluids. Transvaginal
sonogram of a 12-week sac with the echo-free amniotic fluid (AC),
mildly echogenic chorionic fluid (CC), and more echogenic blood
in the subchorionic space (SCH).
AC
CC
SCH

41. 
It is the first structure to be seen normally within the
gestational sac

It os often seen when MSD is 10-15 mm and always be
visualised by an MSD of 20 mm

In TVS, it can be visualised by an MSD of 8 mm

Double decidual sign is not 100% specific for presence of
an IUP, yolk sac within the early gestational sac is
diagnostic of IUP

Yolk sac has a role in transfer of nutrients to the
developing embryo

Angiogenesis occurs in the wall of the yolk sac in the 5th
week
YOLK SAC

42. 
Vascular network in the wall of yolk sac joins the fetal
circulation via the paired vitelline arteriesand veins
through a stalk called vitelline duct

Dorsal part of the yolk sac is incoporated into the embryo
as a primitive gut

The yolk sac remains connected to the mid gut by the
vitelline duct

No. of yolk sacs present can be helpful in determing
amnionicity

In a monochorionic monoamniotic twin gestation, there
will be two embryos, one chorionic sac, one amniotic sac,
and one yolk sac

43. Early sac and embryo. A, Transverse transvaginal sonogram of the anteverted uterus (UT) demonstrates a small
gestational sac at 4 weeks, 3 days. B, Sonogram at 5 weeks, 6 days shows an enlarging gestational sac with the
appearance of a 2-mm yolk sac (arrow). C, Magnified view of the sac reveals a 2.5-mm embryo (calipers); CRL, crown-
rump length. D, M-mode ultrasound shows cardiac motion at a fetal heart rate (FHR) of 107 beats/min (arrow).
A
B
C D

44. Normal yolk sac. A, Nine weeks. B, Eight weeks.
Normal embryo at 8 weeks. Transvaginal
sonogram shows vitelline duct (arrow), yolk
sac (ys), and embryo (e).
Vitelline duct. Three-dimensional (3-D) ultrasound
image of an embryo at 8 weeks with the vitelline duct
(VD) connecting to the yolk sac (YS). There is also a
subchorionic hemorrhage.
A B
e
ys

45. Six-week monochorionic diamniotic (MCDA) twins. Two separate yolk sacs are seen within a single
gestational sac at 6 weeks on 2-D (A) and 3-D (B) images.
A B

46. Normal yolk sac and vitelline duct. Transvaginal scans of 9-week pregnancy focusing on the yolk sac (A)
and flow within the vitelline duct (B and C).
A B
C

47. Monochorionic and diamniotic
Twins with one intrauterine embryonic death and one alive.
Transvaginal sonogram at 10 weeks. On the left the arrow is
pointing to one of two adjacent sacs, one is the amnion and
the other the yolk sac. To the right is a single yolk sac
(calipers) with the live embryo not in the scan plane. Both
embryos went on to abort.

48. Embryo and Amnion

Double-bleb sign as the earliest demonstration of the
amnion

The two blebs represents the amnion and yolk sac and
can be identified as early as five and half weeks when the
crown rump length is 2mm

Amniotic fluid is initially colorless, kidneys begin to
function at about 11 weeks, it becomes pale yellow.

Fluid accumulates at about 5 ml per day at 12 weeks,
amniotic cavity expands to fill the chorionic cavity
completely by 14-16 weeks

Amnion as a separate membrane or sac within the
chorionic cavity before 14-16 weeks

49. Normal 9-week embryo/amnion.
Normal separation of amnion (arrow) and chorionic sacs at 9
weeks. Transvaginal sonography shows the embryo (calipers)
and the amnion (AM).
AM

50. Embryonic Cardiac activity

In normal pregnancies, the embryo can be identified in
gestational sac as small as 10 mm and should be
identified when MSD is 16-18 mm

The tubular heart begins to beat at 36-37 days of
gestational age

Absent cardiac activity may be normal in embryos of less
than 4-5 mm CRL

General cardiac activity can be visualised in normal
embryos of greater than 5 mm CRL

Normal embryonic cardiac activity is greater than 100
beats per minute

51. Normal 6-week embryo. A, Image shows 6-week embryo (calipers) adjacent to the yolk sac. B, M-mode ultra-
sound shows a heart rate of 141 beats/min.

52. Umbilical cord and Cord cyst

The umbilical cord is formed at the end of the 6th week
(CRL=4 mm) as the amnion expands and envolpes the
connecting stalk, yolk stalk and allantois.

Cord contains two umbilical arteries, a single umbilical
vein, allantois, yolk stalk all of which are imbedded in
Wharton's jelly.

Cysts are usually seen in the 8th week and disapperaed
by the 12th week.

Cyst are singular , closer to the fetus with the mean size
of 5.2 mm.

Cysts may originate from remnants of the allantois or yolk
stalk.

53. A B
C
Umbilical cord cyst. A, Live
embryo at 9 weeks’ menstrual
age with a cyst on the cord
(arrow) close to the embryonic
end. On subsequent
examination (not shown) the
cyst was no longer seen. B,
Color Doppler image of the
cord and cyst with flow in the
vessels of the cord and no flow
in the cyst. C, Another example
of a 9 week cord cyst (arrow) in
the midportion of the cord, with
good visualization of the whole
cord, embryo, and yolk sac.

54. Estimation of Gestational Age

Gestational Sac = 5 weeks

Gestational Sac+ yolk sac = 5.5 weeks

Gestational Sac + yolk sac +Embryo = 6 weeks

CRL>5 mm - fetal cardiac activity present

Measure CRL when embryo >7 mm

End of the first trimester measurement of BPD becomes
more accurate than the CRL

55. Early Pregnancy Failure

MSD of equal to or greater than 25 mm without an
embryo

Crown-Rump length of equal to or greater than 7 mm
without cardiac activity

Absence of embryo with heartbeat at 2 or more weeks
after an ultrasound that showed a gestational sac without
a yolk sac

Absence of embryo with heartbeat at 11 days or more
after an ultrasound that showed a gestational sac without
a yolk sac

56. Early pregnancy failure with large, empty sac. A, Transvaginal coronal, and B, transvaginal sagittal,
images of an empty gestational sac. Mean sac diameter (calipers) is 18 mm. No yolk sac is identified.
A B

57. Early pregnancy failure with irregular sac. A, Transvaginal sagittal and transverse views of an irregular empty
gestational sac in a 40-year-old woman with spotting at 11 weeks. Mean sac diameter (calipers) is 25 mm. No
yolk sac or embryo is present, the sac is irregular, and the trophoblast is thin. B, Power Doppler ultrasound
with a small area of vascularity at the implantation site (arrow).
A B

58. Aborting sac. A 23-year-old pregnant woman at 8 weeks’ gestation presented
with cramps and spotting. A, Transvaginal sagittal scan shows a gestational sac
in the lower uterine segment extending into the cervix. B, Sagittal scan of the sac
within the upper cervix. Note the small yolk sac and the adjacent small embryo.
No cardiac activity was detected.
A
B

59. Aborted gestation at 7 weeks, 3 days. A recently aborted but intact sac about 2.8 cm in diameter with an embryo. The
sac was scanned in a water bath so that the frondlike chorionic villi can be seen around the sac floating freely. A and
B, Embryo with 12-mm crown-rump length is attached to the wall by a short umbilical cord. No yolk sac was seen; it
likely regressed. C, 3-D view. D, Sac is floating in a water bath so that the white chorionic villi are seen extending
outward. The villi only cover a portion of the sac. The villi normally degenerate over the area of the sac not at the
implantation site. E, Magnified view of the villi, and F, a vessel within the sac (arrow).
A
B
C
D
E F

60. Collapsed amnion. Transvaginal power
Doppler ultrasound scan of a gestational sac in a 39-year-old
woman who presented with spotting at 9 1 2 weeks. The embryo
is small with a crown-rump length (calipers) of 7 mm, consistent
with 7 weeks. No cardiac activity is seen. The amniotic membrane
(arrow) is collapsed adjacent to the embryo.

61. Sonographic Predictors of Abnormal
Outcome

Embryonic Bradycardia

Mean sac Diameter and Crown-Rump length

Yolk sac size and shape

Low human Chorionic Gonadotropin

Subchorionic Hemorrhage
Amniotic sac abnormalities

62. Fetal bradycardia. A small embryo in a 10-week gestation with a
heart rate of 69 beats/min. This embryo died, and the
pregnancy aborted within 1 week. The embryo is seen within a
round amniotic sac on the left and lies beside a large yolk sac
on the right.

63. Twins: one normal, one with small sac.
A, Transverse transvaginal scan at 8
weeks shows two sacs (A, B), with the
left larger than the right sac. B, At 9
weeks the normal-sized embryo on the
maternal right is of appropriate size,
19.9 mm (calipers), with a normal-sized
gestational sac. The other twin did not
grow normally.

64. Small gestational sac and embryo.
Sagittal transvaginal scan of a 21-year-old woman at 9 weeks’ gestational age with
spotting. There is a small gestational sac that is no larger than the embryo (arrow). The
crown-rump length and mean sac diameter are about equal. No heartbeat was seen.

65. Large yolk sac. Transvaginal scan at 9 weeks shows gestational sac with a small embryo with
bradycardia (not shown) and a large yolk sac (calipers) with mean internal diameter of 5.9 mm. On
follow-up examination 7 days later (not shown), no cardiac activity was identified, indicating
embryonic demise and the yolk sac had become smaller and more echogenic

66. Intrauterine embryonic death with yolk sac
calcification. A, Transvaginal color Doppler
ultrasound scan of a pregnancy at 6 1 2 weeks’
menstrual age (CRL, 6.5 mm) shows an embryo with
no cardiac activity (no color), and a normal appearing
yolk sac (arrow). B, Repeat scan 5 days later shows
no change in the size of the embryo (calipers) and a
dense yolk sac (arrow) with faint distal shadowing. C,
In a different pregnancy, transvaginal sagittal scan
shows calcified yolk sac (ys). No cardiac activity was
identified in embryo with crown-rump length of 18
mm. a, Amnion; e, embryo.
A
B
C
YS e
a

67. Echogenic material within yolk sac. A, Single live embryo at 7 weeks’
gestational age with echogenic material within the yolk sac (ys) next to a
live embryo. B, One week later the yolk sac looks normal, and the
pregnancy continued uneventfully.
A
B

68. Moderate subchorionic bleed. Sagittal transvaginal scan of an 8-week
gestation with no spotting. The moderate subchorionic bleed (*) is seen
adjacent to the gestational sac. The live embryo was not in the field of
view. The bleed resolved and pregnancy continued uneventfully
*

69. Small subchorionic bleed. A, Sagittal
transvaginal scan of a 10-week
gestation with a small subchorionic
hemorrhage (*) elevating the posterior
placental edge in the lower uterine
segment. B, Transverse scan of the
small bleed. C, Sagittal transvaginal
color Doppler ultrasound showing no
flow in the subchorionic bleed.
A B
C
*
*
*

70. Retained Products of Conception

It can have spectrum of sonographic appearances like
empty uterus to a large echogenic mass of tissue filling
the endometrial canal.

Presence of focal increased vascularity is of great
importance in distinguishing between blood clots and
RPOC.

There can be a single vessel or a large group of vessels,
either superficially in the myometrium or extending deep
within it.

Beacuse of the high flow , can raise concern about
performing D&C.

71. Retained products of conception. A, Sagittal transvaginal scan of a 22-year-old woman who presented 5 weeks after a
suction dilation and curettage (D&C) therapeutic abortion with vaginal bleeding. The endometrial canal is distended with
a 1.8 × 2.5–cm echogenic mass (arrows). B, Color Doppler ultrasound shows an area of marked increase in vascularity
at the base of the mass at its attachment to the myometrium. C, Sagittal transvaginal scan of a 28-year-old woman who
had suction D&C for a therapeutic abortion 6 weeks previously with vaginal bleeding. The myometrium in the body
anteriorly was heterogeneous with increased echogenicity. D, Color spectral Doppler ultrasound shows increased
vascularity with velocities of 1.3 m/sec.
A
B
D
C

72. Ectopic Pregnancy

It is the implemetation of the GS anywhere outside the
endometrial cavity.

A pseudosac is an intra utrine fluid collection surrounded
by a single decidual layer as opposed to the two
concentric rings of the doule decidual sign.

Live embryo in the ednexa is specific for the diagnosis of
ectopic pregnancy.

Tubal ring sign (the second most common sonographic
finding), which is the presence of a hyperchoic ring
around the gestational sac.

Ectopic pregnancy most commonly occurs in the
ampullary or isthmic portions of the fallopian tube.

About 26% of ectopic pregnancy have normal pelvic
sonograms on TVS ultrasound.

73. Ruptured ectopic pregnancy with hemoperitoneum. A 35-year-old woman presented at 6 weeks’ gestation with right lower
quadrant pain. A, Sagittal transvaginal scan shows echogenic material within the endometrial cavity but no gestational sac.
Blood clot is (*) seen around the uterus. B, Coronal transvaginal scan of the uterus (U) and a complex right adnexal mass
with a sac at its posterior aspect (arrow). C, Coronal color Doppler sonogram with no vascularity seen. D, Sagittal scan of
the left upper abdomen showing free fluid (*).
A B
C D
*
*

74. Pseudogestational sac. A, Coronal transvaginal scan of a 33-year-old woman (G2P1) at 8 weeks with pelvic
pain. There is a rounded intrauterine sac filled with low-level echoes. No yolk sac or embryo is seen. There is
a single echogenic ring around the fluid (arrow). This is a fluid-filled endometrial canal, a decidual cast, or
pseudogestational sac. B, Sagittal transvaginal scan shows a large pseudogestational sac with echogenic
debris. Note the acute angle at the lower end, uncommon in a gestational sac.

75. Live ectopic pregnancy. A 33-year-old woman presented with left lower quadrant pain at 9 weeks’ gestation. A,
Coronal transvaginal scan shows the empty endometrial cavity on the right and a gestational sac and embryo on
the left. B, M-mode image demonstrates a live embryo with cardiac activity at a rate of 173 beats/min. C, The
embryonic crown-rump length is 19 mm. D, In a different patient, coronal transvaginal scan of the right ovary with
a corpus luteum cyst (c) and a gestational sac with a single live embryo immediately adjacent (arrow).
A B
C D c
RO

76. Isthmic ectopic pregnancy. A 35-year-old woman (G3P1A1) presented with no pain but was at risk for an ectopic
pregnancy. A, Coronal transvaginal scan shows an empty uterus and a tubal ring (arrow) immediately adjacent to
the uterus. B, Magnified view of the ring shows a gestational sac with a yolk sac, confirming an ectopic pregnancy.
C, Color flow Doppler ultrasound shows increased vascularity around the sac with high-velocity flow. D, At
laparoscopy, ectopic site can be seen bulging the isthmic portion of the tube (arrow). It was successfully removed
by salpingostomy.
A
C
B
D

77. Ectopic pregnancy seen as echogenic mass. A 33-year-old woman presented at 7 weeks’ gestation with right lower
quadrant pain. A, Transvaginal scan shows an empty uterus. B, Free fluid (ff ) in the cul-de-sac. C, In right adnexa
there was a 1.4 × 1.6–cm echogenic mass (arrow) adjacent to a normal ovary (ro). The mass was focally tender to
palpation with the vaginal probe. D, Power Doppler ultrasound shows minimal internal vascularity.
A
C
D
B
FF
ro

78. Ectopic pregnancy seen as mixed- echogenicity mass. A 30-year-old woman presented with
left lower quadrant pain at 7 weeks’ gestation and β-hCG of 500 mIU/mL and falling over a 3-
day period. A, In the left adnexa, medial to the left ovary, there was a 2-cm mass (arrow) with
mixed echogenicity, and B, only minimal peripheral vascularity. A left ectopic pregnancy was
confirmed and based on a falling β-hCG was treated expectantly and resolved without
complication.
A
B

79. Interstitial ectopic pregnancy. An 18-year-old woman presented with mild pelvic discomfort with a bulging left cornua. A,
Sagittal transvaginal sac just to the left of midline. The empty endometrial canal is seen in the body of the uterus with
the thin echogenic “interstitial line” (arrow) leading to the interstitial ectopic pregnancy. B, Postoperative specimen of the
wedge resection and removal of the left cornua. C, Coronal transvaginal scan of the expanded left cornua with a thin
myometrial mantle (white arrow), the gestational sac, and the small embryo (black arrow). D, Bisected specimen shows
the sac and the white embryo (arrow) that corresponds to the sonogram in C.
A
C
B
D

80. Cesarean scar implantation. A 33-year- old
woman presented at 10 weeks’ gestation. A,
Transabdominal scan shows a sac (arrow) in
the lower uterine segment. B, Transvaginal
scan shows a sac in the lower segment with
an embryo. C, Magnified view with color
Doppler ultrasound shows flow in a beating
heart and peritrophoblastic flow anteriorly.
Notice how close the echogenic trophoblast
is to the anterior serosal surface of the
uterus and to the bladder wall.
A B
C

81. Heterotopic pregnancy. A 30-year-old woman presented at 6 weeks with pelvic pain and a positive pregnancy test. A, Sagittal
scan shows a retroverted uterus with a normally positioned 6-week gestational sac with yolk sac. B, In the left adnexa,
adjacent to the left ovary (LO), there is a tubal ring (arrow) that proved to be an ectopic sac at laparoscopy.
A B

82. Ectopic pregnancy with hematoma after
methotrexate injection. A, Transvaginal coronal
scan through the uterine fundus shows an early
isthmic ectopic pregnancy in the right adnexa. B,
Three days after intramuscular methotrexate, the
patient returned with increasing pelvic pain.
Transverse scan of the fundus and right adnexa
now shows an echogenic mass (arrowheads)
surrounding the irregular gestational sac (arrow).
C, Sagittal power Doppler ultrasound through the
uterus shows vascularity in the myo- metrium but
not in the hematoma superior to it (short arrows).
A B
C

83. Evaluation of the Embryo

Normal Embryologic Development Mimicking
Pathology
* Intracranial Cystic Structures in First Trimester
* Physiologic Anterior Abdominal wall Herniation

Normal appearing abnormal Embryos
* Anencephaly
* Renalagenesis
* Discrepancy between dates and embryo size

84. Normal embryonic intracranial anatomy. A and B, Sagittal, and coronal images of 9-week embryo (CRL, 19
mm) clearly show the cystic rhombencephalon.
A B

85. Normal lateral ventricles. Transverse scan of a 13-week fetus with choroid
plexus filling most of the lateral ventricles.

86. Physiologic midgut herniation. A, Ten-week embryo has the typical echogenic bowel herniated into the base
of the umbilical cord (arrow). B, 3-D view of an 11-week embryo also shows midgut herniation (arrow).
A
B

87. Anencephaly. Coronal scan of anencephalic fetus at 11 weeks’ gestational age shows a large, irregular
cranial end inferiorly with no visible echogenic calvarium.

88. FIRST TRIMESTER MASSES

Ovarian Masses
* Most common mass seen in first trimester of pregnancy
is the corpus luteum cyst.
* Other cystic masses may present in the first trimester of
pregnancy because of displacement by the enlarge
uterus.
* Torsion, Rupture and Dystocia have all been described
as complication of ovarian cystic masses.
* Dermoid cysts may ne present the characeristic
appearance of a cystic mass with focal calcification and
fluid- fluid level.

89. Hemorrhagic corpus luteum cyst (arrow) at 6 weeks. A, The filamentous bands within the cyst are consistent
with hemorrhage. There is also a paraovarian cyst (p), which is echolucent. B, Hemorrhaging corpus luteum
with a small amount of adjacent free fluid. C, The vascularity is a typical ring of fire with flow in the wall around
the cyst. D, Pathologic specimen of an ovary with a corpus luteum cyst (arrow).
A B
C
D

90. Mucinous cystadenoma of low malignant potential. A, Sagittal scan with the bladder anterior and the cystic
mass posterior compressing the lower segment of the gravid uterus. B, Transvaginal scan shows low-level
echoes within the mass and some debris at the lower end. C, Color Doppler ultrasound shows no flow in the
debris. D, The fluid was aspirated before delivery and was old blood. The mass recurred and was removed at
cesarean delivery.
A
B
C D

91. 
Uterine Masses
* Uterine fibroids are a common palvic mass often
identified during pregnancy and often associated with
localised pain and tenderness.
* Fibroids may distort the uterine contour whereas focal
myometrial contractions usually buldge into the
amniotic cavity.
* Fibroids are associated with almost twice the
spontaneous loss rate in early singleton pregnancies with
documentated cardiac activity.

92. CONCLUSION

First trimester sonography plays an important role in
establishing the location of a pregnancy and determining
if the pregnancy is potentially viable.

Knowledge of the landmarks with respect to the
appearance of the gestational sac , yolk sac and embryo
are important in the appropriate triage of patients.

93. THANK YOU!