2. Types of USG in O& G
Transabdominal USG for obstetric purposes 3-5 MHz
Trans vaginal USG for obstetric puposes 5-7.5 MHz
Transabdominal Transvaginal
Bladder should be full for transabdominal
scan as it creates good echo
Bladder should be empty
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3. Timing of USG
First scan 7 weeks of gestation • Confirm pregnancy
• Exclude cardiac or molar
pregnancies
• Cardiac pulsation
• Measure CRL
Second scan (anomaly scan) 18-20 weeks • Look for congenital anomalies
Third scan 32 weeks or later • To assess fetal growth & fetal size
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4. Diagnosis & confirmation of pregnancy by
USG
Gestational sac 4^1/2 weeks of gestation
Yolksac 5 weeks
Cardiac activity 6 weeks
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5. Site of pregnancy
• Trans vaginal USG IOC for unruptured ectopic pregnancies
• Absence of gestational sac in uterus
• Fluid in POD
• Extraovarial complex adnexal mass most sensitive & specific
• Pseudosac in uterus
• Tubal ring or echogenic ring doughnut sign
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8. Double decidual sign
• Normal USG appearance of
IU gestational sac
• Seen as 2 concentric
echogenic rings separated by
hyperechoic space
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12. Fallopian tube in ectopic pregnancy
• d/t hypervascularity
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13. Tubal ring or echogenic ring
• Non ovarian hypoechoic ring ring like mass
• Surrounded by fluid
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14. Bagel sign in ectopic pregnancy
• Ultra sonographic sign of ectopic pregnancy
• Gestational sac in the adnexa with hyperechoic ring
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15. Vaginal bleeding in early pregnancy
Viability can be assessed by cardiac activity
• Visible heart beat by pulsed Doppler @ around 6 weeks
• Clearly depicted by 7 weeks
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16. Molar pregnancies
• Best diagnosed by USG
• Snow storm appearance
• Complete mole appears like
echogenic with numwerous
anechoic cyst like spaces
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17. Snow storm appearance
• In hydatidiform mole
• Snow storm appearance in chest
• Mets from thyroid
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18. Bunch of grapes sign in molar pregnancy
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19. Diagnosis of fetal malformation
• Anomaly scan done @18-20 weeks
• Earliest anomaly which can be detected is anencephaly
• Detected@ 10-11 weeks
Signs in spina bifida
Lemon sign Compression or flattening of the
posterior cerebellar surface
making a crescentic appearance
Banana sign Concave deformity of the frontal
bones
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24. Gestational age assessment
1st trimester Crown Rump length (CRL)
2nd trimester Corrected biparietal diameter (cBPD) or head
circumference (HC)
3rd trimester Head circumference and femur length
• Crown rump length is the best
• Transcerebellar diameter (TCD) is an accurate predictor
of gestational age when measured between 14 and 28
weeks.
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25. Fetal growth assessment
• Best indicator of fetal growth - Abdominal circumference
• best USG parameter to detect IUGR is Abdominal circumference
• best USG parameter to detect Macrosomia is Abdominal circumference
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26. Butterfly sign
• Normal feature
• Normal appearance of choroid plexus on axial
imaging of fetal brain
• Absence of butterfly sign holoprosencephaly
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27. TVS
• It is more informative in first trimester.
• In TVS images are of enhanced quality (5–7.5 MHz transducer).
• Full bladder is not required.
• It is superior to transabdominal USG in placenta previa.
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28. • Use of transvaginal probe can detect the following events by one
week earlier then transabdominal.
• 1. Gestational ring - 5th week
• 2. Fetal poles - 6th week
• 3. Yolk sac - 6th week
• 4. Cardiac pulsation - 7th week
• 5. Embryonic movement - 8th week
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29. T sign in monochorionic monoamniotic
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34. Signs of IUD
Spalding sign Overlapping of sutural bines
Roberts sign Air in great vessels
Ball sign Crumpled up spine of fetus
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42. Umbilical A Doppler
Systolic / diastolic ratio
< 2.5 Normal
>3.0 IUGR Decreased absent or reversal of
diastolic flow impending fetal
demise
>3.5 in last trimester Terminate pregnancy
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