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OB Ultrasound > Fetal Biometrics and Fetal Lie > Flashcards

Fetal Biometrics and Fetal Lie Flashcards

1
Q

The very first thing that should be evaluated in a second/third trimester US is the ___.

A

cervix

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2
Q

Does the patient ever need to have a full bladder?

A

No.

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3
Q

If the patient has a full bladder, what might the radiologist misdiagnose?

A

Placenta previa. The lower uterine segment gets pressed together and can appear as an extensively long cervix.

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4
Q

If the fetal head lies close to the cervix and causes shadowing, what can be done to reposition baby to get better images of the cervix?

A

Trendelenberg mother. (head lowered) Gravity will assist the baby away from the cervix. If this needs to be done, do it LAST! It can make mom sick.

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5
Q

Normal length of a closed cervix is:

A

2.8 to 5 cm

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6
Q

The cervix has an echogenic ___ ___ in it, Measure this and you will have a true cervical length.

A

mucous plug

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7
Q

Whatever fetal structure is ___ to the cervix determines the presentation of the baby.

A

adjacent

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8
Q

There are three fetal presentations. Name and describe them.

A

Breech- fetal bottom presents.
Cephalic- fetal head presents
Transverse- fetal back or abdomen presents. (Must also note where the head is in this case, maternal right or left.)

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9
Q

AFI will be measured in ___ quadrants and the normal range is _____ cm of amniotic fluid.

A

four, 5-25cm

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10
Q

Largest single vertical pocket can also be measured with a normal range of ___ cm of amniotic fluid.

A

2-10

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11
Q

When evaluating the placenta you must note the ____, and if it is close to the cervix, ____ the distance between the placental edge and cervix.

A

location; measure

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12
Q

If you have an ANTERIOR placenta that is low lying or previa, with history of a Csection, ____ ____ can occur.

A

placental invasion

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13
Q

When you see an anterior placenta, you should ask the patient if they have ever had a ___ ___.

A

Cesarean section

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14
Q

Dating the pregnancy can be done using these four biometric measurements. This is the most accurate method for dating second/third trimester pregnancies.

A

Head circumference
Biparietal diameter
Abdominal circumference
Femur length

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15
Q

What are the four structures to be measured in the fetal head?

A

ventricular size, cerebellar size, cisterna magna, and nuchal fold

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16
Q

Nuchal fold is only measured in fetuses under ___ weeks. The normal value is less than ___mm.

A

24; 6

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17
Q

Name the two structures generally imaged on the fetal face.

A

lips and nares

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18
Q

The heart image should demonstrate all ___ chambers and septum. The heart rate should only be measured in ___. It is also a good idea to document the diaphragm in a ___ plane.

A

4; M mode; sagittal

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19
Q

The fetal abdomen must be imaged in a ___ plane to demonstrate the stomach in the __ __ __ , as well as the ___ insertion.

A

transverse; left upper quadrant; cord

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20
Q

There are two ways to prove a 3 vessel cord. Explain them.

A

1) a transverse view of the cord itself which will appear as a Mickey Mouse- The face is the umbilical vein and the two ears are the umbilical arteries.
2) an image of the urinary bladder in transverse with color flow demonstrating the two umbilical arteries on either side of it; by definition if the baby is alive it also has the umbilical vein.

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21
Q

A transverse image of the kidneys and bladder must be obtained, and the bladder should fill at least once within ___ minutes.

A

30

22
Q

Should you ever mark “boy” or “girl” on films for the patient?

A

NO- potential lawsuit

23
Q

What is the accuracy rate of dating a pregnancy in the first trimester? Second trimester? Third trimester?

A

1 2 3 Rule… First trimester within 1 week
Second trimester within 2 weeks
Third trimester within 3 weeks

24
Q

What is the most accurate measurement of gestational age in a first trimester pregnancy?

A

CRL crown rump length

25
Q

What is the Angle of Asynclitism?

A

For an exact BPD, the angle of the transducer (sound beam) should be exactly 90 degrees to the fetal cranial sagittal suture.

26
Q

The BPD should be measured from ___ surface of the skull closest to the transducer to the ___ margin of the opposite skull table.

A

outer; inner

27
Q

The fetal head should be imaged in a __ plane. Intracranial landmarks include the ___ and ___anteriorly, the __ __ in the atrium of each lateral ventricle, and the ___ ___ in the midline.

A
  • -transverse
  • -falx, CSP (cavum septum pellucidum)
  • -choroid plexus
  • -thalamic nuclei (paired walnuts)
28
Q

The fetal head circumference is measured by an __ ___on the US machine.

A

ellipse toggle

29
Q

The cephalic index determines the head shape and is determined by dividing the __ __ by the occipital frontal diameter. The is part of the software package.

A

biparietal diameter

30
Q

Normal range for a cephalic index is ____.

A

.72-.86 OR 70%-86%

31
Q

___ is when the cephalic index is less than .72 or 72%. ___ is when the cephalic index is greater than .86 or 86%

A

Dolicocephally (long head)

Brachycephally (short head)

32
Q

Abdominal circumference (AC) is best imaged and measured at the level of the __ and __ __ __. The spine should be seen ___. This measurement is made outer to outer with the ellipse toggle and includes __ and ___.

A

stomach, left portal vein
posteriorly
fat and skin

33
Q

If the abdominal circumference falls more than two standard deviations below the mean for gestational age, you should look for other signs of ___.

A

IUGR

34
Q

The least reliable biometric measurement is the __ __.

A

abdominal circumference; due to the physiologisc variation in babies, especially after 25 weeks

35
Q

Always measure the femur ___ to the transducer, The ___ femur can be distorted due to artifactual bowing.

A

nearest; farthest

36
Q

When measuring the femur, do not include the ____ on either end.

A

epiphysis

37
Q

If the femur length falls below two standard deviations, other signs of __ __ must be excluded.

A

skeletal dysplasia

38
Q

What is Nageles Rule?

A

This is a non US way to determine due date. The formula is:

Due Date= LMP - 3 months + 7 days

39
Q

The ___ measurement is roughly equal in weeks to the age of the fetus up to 24 weeks. then all bets are off.

A

cerebellar

40
Q

Is US accurate in predicting baby weight?

A

No. It is more for evaluating fetal growth.

41
Q

What is a BPP and what is it used for?

A

Biophysical profile.

Used to detect fetal asphyxiation or suffocation

42
Q

What four parameters are tested in a BPP and how is it scored?

A

Within 30 minutes fetal breathing (develops at 24 weeks), gross body movements (develops at 19 weeks), fetal tone (develops at 14 weeks), and AFI are all surveyed. They are each given either a zero (not seen) or a two (seen) for a total possible score of 8.

43
Q

If a fetus is asphyxiating what will be the first BPP parameter to disappear? What is the last?

A

Fetal breathing stops first, fetal tone will go last.

44
Q

A non stress test measures heart rate ___ and should show at least two episodes of accelerated fetal heart rate of greater than __ bpm for __ seconds over a 30 minute period. This is the most advanced non-US parameter.

A

reactivity; 15; 15

45
Q

Fetal lie can be defined as:

A

where the baby’s long axis is in relation to the mother’s long axis. It can be longitudinal, transverse, or oblique.

46
Q

The most common presentation of a fetus is:

A

cephalic- head presenting

47
Q

In twins, which baby will ALWAYS be labeled as Baby A throughout an entire pregnancy?

A

Baby A will always be the one closest to the cervix

48
Q

What are the four degrees of cephalic presentation?

A

1) vertex-(most common 95%) parietal bones presenting
2) sinciput-deflected vertex
3) brow-eyebrows present
4) face- face presents

49
Q

Define breech and what are the four types.

A

Breech is any presentation where the fetal head is in the uterine fundus and the lower extremities or bottom presents.

1) footling-feet presenting
2) Frank-hips flexed, knees extended (baby kissing knees)
3) complete- hips flexed, knees flexed (fetal position)
4) shoulder- shoulder presenting

50
Q

Be the baby ya’ll.

A

I just threw it in here to see if you’re paying attention :)

OB Ultrasound (24 decks)

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