Indications of first timester early USG Method of reporting Findings of early pregnancy failure

1. OBSTETRIC USG

2. Indications for First-Trimester Ultrasound
• Confirmation of the presence of an IUP
• Suspected ectopic
• Vaginal bleeding / Pelvic pain
• Estimation of gestational age
• Diagnosis or evaluation of multiple gestations
• Confirmation of cardiac activity

3. • Adjunct to chorionic villus sampling, embryo transfer, and
localization, and removal of an intrauterine device
• Assessment for certain fetal anomalies, such as anencephaly,
in high-risk patients
• Measurement of nuchal translucency when part of a
screening program for fetal aneuploidy
• Suspected ectopic pregnancy
• Suspected hydatidiform mole
• Maternal pelvic masses and/or uterine abnormalities

4. FIRST TRIMESTER USG

5. General Survey Guidelines for First-Trimester
Ultrasound
• Gestational sac Location of pregnancy: intrauterine vs.
extrauterine
• Gestational age (as appropriate) - Mean sac diameter/
Embryonic pole length or crown rump length
• Yolk sac
• Cardiac activity on M-mode ultrasound
• Embryo/fetal number (amnionicity/chorionicity)
• Maternal anatomy: uterus and adnexa

6. • A definitive diagnosis of intrauterine pregnancy can be made when an
intrauterine gestational sac containing a yolk sac or embryo with
cardiac activity is visualized.
• A small, eccentric intrauterine fluid collection with an echogenic rim
can be seen before the yolk sac and embryo are detectable in a very
early intrauterine pregnancy

7. GESTATIONAL SAC
• The first reliable gray-scale evidence of an IUP is visualization of a
small (1-2 mm fluid collection surrounded by an echogenic rim)
gestational sac within the thickened decidua.
• - Intradecidual sign, seen at about 4.5 weeks’ gestation
• Double-decidual sign - method for distinguishing between an early
IUP and an endometrial fluid collection of other origin, such as the
pseudosac of an ectopic pregnancy.
• A well-defined double-decidual sign is an accurate predictor of the
presence of an IUP

8. Intradecicual sign
• Intradecidual g sac located
eccentrically within the
endometrium.
• Sac has echogenic rim

9. Double decidual sign
• Sagittal TVS at 5 weeks 6
days shows the decidua
capsularis around the
gestational sac and the
maternal decidua vera as
separate echogenic bands.

10. • The gestational (or chorionic) sac
is filled with extracoelomic or
chorionic sac fluid, which is
normally weakly reflective and
more echogenic than the
amniotic fluid

11. Measurements in three
orthogonal planes are averaged
to calculate the mean sac
diameter. Note yolk sac within
the gestational sac.
Mean sac diameter

12. • The crown-rump length is a more accurate indicator of gestational age
than is the mean gestational sac diameter.
• The mean gestational sac diameter may be recorded when an embryo
is not identified.

13. Serum B-HCG
• Complementary role with ultrasound in the evaluation of early
pregnancy
• The serum β-hCG test yields positive results at approx 23 days of
gestational age before a normal intrauterine gestational sac may be
imaged with TVS
• The threshold level identifies the earliest one can expect to see a sac,
and the discriminatory level identifies when one should always see
the sac

14. Yolk Sac
• The secondary yolk sac is the first
structure to be seen normally
within the gestational sac(primary
yolk sac regress at 4 wks)
• TVS- MSD 8mm
• TAS- MSD 10-15mm
• Identification of a yolk sac within
the early gestational sac is
diagnostic of IUP- can differentiate
from pesudosac.

15. • YS seen separate from embryo- 9wks

16. Functions of YS
• Transfer of nutrients(3-4 wks)
• Angiogenesis(wall of YS in 5th week)- joins embryonic
circulation via vitelline arteries and veins through vitelline
duct
• Hematopoesis- in vascularised extra embryonic mesoderm
covering the YS(5th week)
• Dorsal part of YS- primitive gut

17. • TVS shows vitelline duct

18. • No.of YS= No.of Amnion. – So, no.of YS determine
Amnionicity in multifetal pregnancy
• MCMA- 2 embryo, one chorionic sac(g sac), one amniotic sac
• MCDA- 2 embryo, one chorionic sac, 2 amniotic sac

20. Embryo and Amnion
• Amnion becomes visible when the embryo has a CRL of 2
mm at 6 weeks.
• The cavity becomes almost spherical by about 7 weeks
• Initially- colourless(fetal dermal transudate), later when
kidneys develop- 11 wks- pale yellow
• Rapid increase in fluid- 9 wks
• 5 mL per day at 12 weeks.

21. • Amniotic cavity expands to fill the chorionic cavity completely
by week 16.
• If fail to juxtapose- Unfused amnion
• Iatrogenic or spontaneous rupture of the amniotic membrane
in the first trimester is a rare occurrence and even more rarely
results in the amniotic band sequence.

22. Abnormal Amnion
• Empty Amnion- with
no embryo at 9 wks

23. • Expanded amnion- abnormally
large amnion at 7wks

24. Embryonic cardiac activity
• Embryo can be identified in gestational sacs as small as 10 mm and
should always be identified when the MSD =/>25 mm
• Using TVS, cardiac activity is typically seen by the time an embryo is 2
mm in size, and is almost always seen by 5-mm CRL.
• For strict diagnosis of nonviable pregnancy the threshold is set at
7 mm CRL

25. • Embryonic cardiac activity is greater than 100 bpm when the embryo
is less than 6.3 weeks and 120 bpm at or beyond 6.3 week
• If <100bpm – should follow up

27. Umbilical cord
• Formed at the end of the sixth week (CRL = 4.0 mm) as the amnion
expands and envelops the connecting stalk, the yolk stalk, and the
allantois
• Two umbilical arteries,
• single umbilical vein,
• Allantois,
• Yolk stalk (also called the omphalomesenteric duct or vitelline
duct), all of which are embedded in Wharton jelly.

28. • UA- Superior vesical artery & Medial Umbilical Ligament
• UV- ligamentum Teres
• Allantois- Bladder development- becomes Urachus & Median Umbilicl
ligament
• Yolk stalk- connect primitive gut to YS- contain vitelline art and veins

29. • UC cysts- 8Th week- 12th wk
• Singular, closer to fetus/
embryo than to placenta;
mean size 5.2mm

30. Estimation OF Gestational Age

31. G Sac Size
• Menstrual age in days = MSD (in mm)+ 30.55
• The MSD increases in size at a rate of 1.1 mm per day.
• If MSD is very small, about 2 mm, gestational age is 4 to 4 1 /2 weeks,
and MSD of about 5 mm is 5 weeks

32. Crown-Rump Length
• Once the embryonic pole is visualized (just before 6 weeks),
measurement of the CRL of the embryo is considered the most
accurate method to date the pregnancy

33. ASSESSMENT OF PREGNANCY NUMBER

34. • The number determined on an early first trimester scan may
subsequently increase or decrease, owing to the “vanishing” and
“appearing” twin phenomena

35. Vanishing Twin
• 1) pregnancies that began as twins, with one of the
gestations failing to progress beyond an early stage
• (2) singleton pregnancies with a second fluid collection
• Loss of one twin can occur at any time during pregnancy but
is most common during the early first trimester
• Likelihood of loss of one twin is greatest if the twins are
monochorionic or the woman has symptoms of vaginal
bleeding at the time of the initial scan

36. Vanishing twin

37. Appearing twin
• Prior to 6 weeks, when the embryo may not be visible, the
assessment of number is more prone to error. At that stage, it is done
by counting gestational sacs and yolk sacs.
• When more than one gestation implants in the uterus, one or more of
them might not be visible at the time of the initial scan because of its
small size or location.

38. Appearing twin

39. • Monochorionic twins scanned prior to visualization of yolk
sacs (i.e., before about 5.5 weeks) will always be mistaken for
a singleton gestation, as will monochorionic monoamniotic
twins scanned prior to visualization of embryos (i.e., before
about 6.0 weeks), because monoamniotic twin gestations
typically have only a single yolk sac

40. EARLY PREGNANCY FAILURE

41. CAUSES • Chromosomal anomaly
• Luteal phase defect
Advanced maternal age (>35) and low serum β-hCG (<1200 mIU/ml)-
associated with increase risk of failure

42. Diagnostic findings of Early Pregnancy Failure
• CRL of 7mm without Heartbeat
• MSD of 25mm without Embryo
Combination of vaginal bleeding and absent cardiac
activity in embryos of CRL less than 5 mm on TVS is
associated with a very poor prognosis

43. Findings Suspicious for pregnancy failure:
(1) an initial scan shows a gestational sac without yolk sac or
embryo, and there is no visible embryo with a heartbeat on
a subsequent scan 7 to 13 days later, and
(2) an initial scan shows a gestational sac with yolk sac but no
embryo, and there is still no visible embryo with a heartbeat
on a subsequent scan 7 to 10 days later.

44. Empty Amnion Sign
• The normal order of visibility of structures within the early
gestational sac is yolk sac, then embryo, then amnion.
• It can be normal to see an embryo and no amnion but not to see an
amnion and no embryo.
• The latter combination has been termed the empty amnion sign.
• This sign is present when the gestational sac contains two adjacent
circular structures, representing the yolk sac and amnion, but no
embryo

46. Expanded amnion

47. Enlarged YS
• >7mm

48. Worrisome findings
CRL >7mm and no heart
beat
Embryo 2-6 mm without cardiac activity is a
worrisome finding. Follow-up is needed to assess
for cardiac activity in 1 week to ensure 100%
specificity in diagnosis of miscarriage.
Gestational sac with MSD 16-
24 mm and no embryo
Embryo is typically seen by the time the MSD is 16
mm. Follow-up in 10-14 days is needed to ensure
100% specificity in diagnosis of miscarriage.
FINDINGS Comments

49. Gestational sac appearance Irregular, Low position, weak Decidual
Reaction
Small MSD in relation to CRL MSD-CRL <5. Also termed Early
Oligamnios
Abnormal Amnion Empty/ Expanded Amnion
Yolk sac >7mm/ Calcified YS Calcified – echogenic material- 36 hrs
after fetal demise

50. Embryonic Bradycardia <100bpm
Large Sub Chorionic H’ge Elevation of the placental margin
or marginal sinus rupture

51. Irregular G sac, positioned low in uterus

52. Calcified YS

53. • Chorionic bump and small
marginal SCH