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
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
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
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
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 ovumEmbryonic demise
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
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
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