OB imaging Flashcards

1
Q

What is the difference between transabdominal & transvaginal ultrasounds?

A

Transvaginal
- more sensitive
- empty bladder
- used only before 12 weeks

Transabdominal
- full bladder
- affected by maternal BMI
- used in all trimesters

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2
Q

What are the indications for ultrasound in the first trimester?

A

1- diagnosis of pregnancy, location, viability, # of fetuses
2- dating scan: crown rump length 45-84mm
3- nuchal translucency
4- vaginal bleeding or acute abdominal pain

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3
Q

What are the indications for ultrasound in the second trimester?

A

1- anomaly scan
2- growth scan
3- measurement of cervical length

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4
Q

What are the indications for ultrasound in the third trimester?

A

1- growth
2- fetal wellbeing assessment: amniotic fluid volume & doppler ultrasound
3- placental localization (esp cases of antepartum hemorrhage)
4- presentation of delivery

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5
Q

When should gestational age be determined?

A

MAXIMUM by 20 weeks

from 14 weeks & more use HC, BPD, & FL for dating

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6
Q

What is the best time for detection of anomalies?

A

18-21+6 days
detection rate 40-90% at 20 weeks

  • depends on type of anomaly, position of fetus, & maternal BMI
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7
Q

When should cervical length be measured?

A

second trimester at 16 weeks transvaginally
- ladies with previous history of preterm labor
- history of mid trimester loss

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8
Q

What is a low lying placenta?

A

less than 2cm between placental edge & cervical os
- transvaginal evaluation
- recheck it at 32 weeks

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9
Q

How is the amniotic fluid volume measured?

A
  • deepest vertical pole: normally 2 - 8 cm
  • amniotic fluid index: normally 10 - 25cm
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10
Q

What is seen using the doppler ultrasound?

A
  • middle cerebral artery -> increased in fetal anemia
  • uterine artery doppler -> in fetal growth restriction
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