First trimester ultrasound

ultrasound course 2015

1. FIRST TRIMESTER ULTRASOUND

2. TVS advantages
Shorter probe-target distance
Allows use of higher frequency probes
Better image resolution
Avoids problem of under/over distended
bladder
Earlier dx of fetal viability / ectopic
pregnancy
Very useful in retroverted uterus or
obese patients

3. TVS disadvantages

Cost
 Limited depth of penetration
 Lacks global picture
 Difficulty in evaluation of large masses
 ? Relatively invasive

4. Bladder
Uterus
TAS
TVS
LONGITUDINAL VIEW

5. TRANSVERSE VIEW

TAS TVS

6. INDICATION
•First Trimester Ultrasound Screening
–Should be selective and restricted to
specific indications

7. Confirmation of pregnancy viability
Established accurate gestational age
Determine the number of fetuses
Assess chorionicity and amniocity fetuses
Imaging as an adjunct to chorionic villus sampling,
embryo transfer, and localization and removal of
an intrauterine device

8. Common Indications
•Amenorrhoea
•Pelvic pain
•Vaginal bleeding
•Unknown last normal menstrual dates
•Subjective feeling of pregnancy
•Uterus greater or smaller than dates on clinical
evaluation
•Pregnancy test positive or increased hCG values
•Nuchal translucency measurement

9. ?Last Menstrual Period
The LMP is unreliable (and therefore Naegele’s
formula cannot be used) if the:
● date of the LMP is not accurately known
● menstrual cycle is not 28 days long
● menstrual cycle is irregular
● woman has only stopped taking the combined
oral contraceptive pill (‘the pill’) within the last
3 months
● woman has bled in early pregnancy
● woman is breast feeding or has been pregnant in
the preceding 3–6 months.

10. Pregnancy Development in Early TM
Gestational
weeks
Ultrasound Features
TVS TAS
4 4-5 gestational sac
Round shape, internal cystic echo
Two layers wall -
5 6-7 Embryo - fetal pole and yolk sac
5-6 7-8 Fetal heart beats, fetal head,body
and extremities are observed
8-9 9-10 Placenta and ventricles are seen

11. Intrauterine GS

12. IUGS vs Pseudosac
pseudosac
IUGS

13. Still CONFUSED???

17. problem
Should see on TVS Time of visualization
Findings Gestation week or
measurement
Beta HCG level
Gestation sac

5 menstrual weeks
Yolk sac

when MSD is >7mm
Embryonic pole 5 weeks

2000 mIU/mL
Fetal heart
activity
when CRL is >5 mm

18. Estimation of Gestational Age

19. Estimation of gestational age

20. CROWN RUMP LENGTH

21. Crown Rump Length (CRL)
•This measurement can be made between 7 to
13 weeks and gives very accurate estimation
of the gestational age.
•Dating with the CRL can be within 3-4 days of
the last menstrual period

24. MULTIPLE PREGNANCY

25. T sign Lambda sign

28. Failing Pregnancy/ Failure

29. Diagnostic Signs of Early Pregnancy Failure
in the First Trimester

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 with a yolk sac

30. TVS TAS
GS > 25 mm without yolk
sac
EMBRYO > 7 mm > 9 mm

31. Transvaginal ultrasound
Embryonic demise
Blighted ovum
Transabdominal ultrasound
Embryo >5mm
No cardiac activity
Embryo >9mm
No cardiac activity
Gestational sac > 8 mm
No yolk sac
Gestational sac > 20mm
No yolk sac
Gestational sac > 16 mm
No embryo
Gestational sac > 25 mm
No embryo
Blighted ovum Embryonic demise

32. Early Trimester Pregnancy
Development

33. Thickened endometrium

34. 4 – 5 weeks
TAS TVS

35. 5 – 6 weeks

38. 6 – 7 weeks

39. 7 – 8 weeks

40. 7 – 8 weeks

41. 9 weeks

42. 10 weeks

43. Nuchal Translucency

45. NUCHAL TRANSLUCENCY (NT)

•11 to 14 wks
•=/> 3 mm
•Abnormal NT may indicates:
–1. chromosamal abnormality
•Trisomy 21 or 18 or 13
•Turners Syndrome
–Cardiac abnormality
–Prediction of TTTS (4 fold increase in risk)

46. First Trimester Fetal Defect
•Acrania/Anencephaly
•Holoprosencephaly
•Encephalocele
•Dandy-walker Syndrome
•Univentricular heart
•Gastrochisis
•Exomphalos
•Multidysplastic kidneys

48. Should First Trimester US be routine?
•Determination of EDD
•Optimise the time for fetal anomaly scan
•Enhance performance of serum screening test
•H/O ectopic pregnancy/miscarriage
•Intrauterine / ongoing pregnancy
•Diagnosed early unanticipated miscarriage
•Better informed when to deliver which
complication arise in second or third trimester
•Minimise false positive IOL for postmaturity
•Multiple pregnancy and chorioamniocity can
be determined

49. Ectopic pregnancy

50. •35 - 50% with TAS
•95% with TVS
•Gestational sac with viable embryo in
fallopian tube (12%)
•complex mass high sensitivity (98%)

Adnexal Mass

51. •Not seen in 20% of ectopics
•May be seen in normal patients

Fluid in POD

52. consider
•patient not pregnant
•early pregnancy
•ectopic pregnancy
•Use beta hCG
•Must see IUGS with TVS if hCG levels of
2000 IU and above
•KIV repeat hCG every 2 days if very early

Failure to visualize intrauterine GS

53. GUIDELINES FOR DATING PREGNANCY
STAGE OF
DEVELOPMENT
GESTATIO-NAL
AGE (WEEKS)
LEVEL OF B-HCG
Gestational sac 5 weeks 1,000-2,000
mIU/L
Gestational sac with
yolk sac
5.5 weeks 7,200 mIU/L
Gestational sac with
yolk sac & embryo
6 weeks 10,800 mIU/L

58. Molar pregnancy

59. Complete Mole

60. Snowstorm Appearance

61. Theca Lutein Cyst in Molar Pregnancy

64. Biometric Measurements of the Basic Obstetric
Ultrasound Examination
Mean sac diameter if no embryo is seen
Crown-Rump
Length
up to 13 6/7 weeks
gestation
Biparietal Diameter >13 6/7 weeks gestation
Head
Circumference
>13 6/7 weeks gestation
Abdominal
Circumference
>13 6/7 weeks gestation
Femur Length >13 6/7 weeks gestation

66. THANK YOU