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OB/GYN Scanning > Fetal Age & Measurements > Flashcards

Fetal Age & Measurements Flashcards

1
Q

Sonographic measurements of the fetus provide info about…

A
  1. fetal age
  2. EFW
  3. diagnose growth disturbances
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2
Q

This is the true measure of age, the number of days since conception.

A

conceptual age

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3
Q

This is the number of days since the first day of the last menstrual period.

A

menstrual age

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4
Q

Accurate knowledge of gestational age is important…

A

Telling normal from abnormal and timing of …

  1. CVS
  2. amnio
  3. elective induction
  4. cesarean
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5
Q

Dating by LMP may be inaccurate because of…

A
  1. variability of cycle length
  2. faulty memory
  3. oral contraceptives
  4. bleeding during early pregnancy
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6
Q

Determining gestational age from fundal height may be affected by…

A
  1. uterine fibroids
  2. multiple pregnancy
  3. maternal body habitus
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7
Q

From 5-6 weeks, there are two methods for assigning gestational age. They are?

A
  1. MSD

2. contents of the sac

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8
Q

This is the average internal diamter of the sac.

A

MSD

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9
Q

The sac is _mm at 5 weeks and _mm at 6 weeks.

A

2, 10

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10
Q

You should only use the MSD for dating if..

A

you don’t see an embyro.

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11
Q

If the difference between the MSD and the CRL is 5 mm or less there’s a high risk of…

A

spontaneous abortion.

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12
Q

The heartbeat should always be seen from __ weeks onward.

A

6.3

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13
Q

The term ‘embryo’ applies until the __ week.

A

10

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14
Q

CRL correlates closely with GA until around the __ week.

A

13

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15
Q

What are the main measurements in the 2nd and 3rd trimesters?

A
  1. BPD
  2. HC
  3. AC
  4. FL
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16
Q

If the AC is too short, look for signs of…

A

IUGR.

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17
Q

If the FL is too short, look for signs of…

A

skeletal dysplasia.

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18
Q

What are the three head measurements?

A
  1. BPD
  2. OFD
  3. HC
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19
Q

BPD measures from the ___ edge of the near side of the cranium to the ___ edge of the far side of the cranium.

A

outer, inner

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20
Q

What anatomic landmarks do you need to measure the BPD?

A
  1. symmetrically postioned thalami
  2. cavum septum pellucidum
  3. falx
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21
Q

Sonographically, this refers to the relationship between the fetal cranial sagittal suture and the central portion of the u/s beam.

A

angle of asynclitism

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22
Q

For an exact BPD, the angle of asynclitism should be…

A

90 degrees to the cranial sag suture

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23
Q

This is the length of the outer perimeter of the cranium, made at the same level as the BPD.

A

HC

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24
Q

T/F? HC should include scalp echoes when using the ellipse method.

A

FALSE, should not

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25
Q

This is the measure of the long axis of the fetal head, at the same level as the BPD.

A

OFP

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26
Q

The OFP should be measured from the ___ edge to the ___ edge.

A

outer, outer

27
Q

In this condition, the AP length of the fetal head is shortened.

A

brachycephaly

28
Q

In this condition, the AP length of the fetal head is lengthened.

A

dolicocephaly

29
Q

This is obtained by measuring the widest and longest dimension of the fetal skull.

A

cephalic index (CI)

30
Q

This should be used to evaluate the validity of the BPD, if the head is an unusual shape.

A

CI

31
Q

What’s the normal range for CI?

A

75%-81%

32
Q

This is the length of the outer perimeter of the fetal abdomen.

A

AC

33
Q

At what level is the AC measured?

A

With the stomach and LPV visible

34
Q

The AC should not be taken if the spine is at what position?

A

12 (or 6) o’clock

35
Q

T/F? When taking an AC, the fetal abdomen should be round, not elliptical.

A

true

36
Q

T/F? When taking an AC, the ellipse should not contain skin echoes.

A

FALSE, should

37
Q

T/F? Gestational diabetes causes the fetal abdomen to enlarge.

A

true

38
Q

This is a measurement of the ossified diaphysis of the femur.

A

FL

39
Q

T/F? The distal femoral epiphysis (spike) should NOT be included in the FL.

A

true

40
Q

T/F? Sonography is an accurate predictor of fetal weight, especially in the 3rd trimester.

A

FALSE, inaccurate

41
Q

This measurement is taken of the fetal orbits, to include the bridge of the nose.

A

binocular distance

42
Q

This is a condition of the eyes being too close together, frequently present with…

A

hypotelorism, holoprosencephaly.

43
Q

This is a condition of the eyes being too far apart, seen in cases of…

A

hypertelorism, cleft syndromes and frontal cephaloceles.

44
Q

This may be useful in assessing GA in growth restricted fetuses or if baby’s head in not in a good position.

A

transcerebellar distance

45
Q

Transcerebellar distance is equivalent to menstrual age from __ weeks.

A

14-20

46
Q

Normal fetal kidneys between week 32 - term usually measure…

A

4-4.5 cm

47
Q

An off-axis nasal bone length will produce an ___ measurement.

A

erroneous

48
Q

A nasal bone that is not visible or with a length of less then 2.5 mmm is called…

A

nasal hypoplasia

49
Q

A baby who is LGA has a weight above the…

A

90th percentile for gestation age.

50
Q

Macrosomia is most often defined on the basis of a weight above…

A

4000 g.

51
Q

Name some risk factors for LGA and macrosoma.

A
  1. maternal obesity
  2. diabetes
  3. previous LGA infant
  4. prolonged pregnancy
  5. excess pregnancy weight
  6. multiparity
  7. advanced maternal age
52
Q

This is a fetal growth disorder most commonly defined on the basis of weight below the 10th percentile for gestational age.

A

IUGR aka SGA

53
Q

Most cases of growth restriction are caused by…

A
  1. placental insufficiency
  2. maternal HTN
  3. collagen vascular disease
  4. poor nutrition or substance abuse
54
Q

Less common causes of growth restriction are…

A

trisomy 18 or intrauterine infection

55
Q

This fetal condition can be categorized as symmetrical or asymmetrical.

A

IUGR

56
Q

This is a system designed to detect fetal asphyxia.

A

BPP

57
Q

What are the BPP parameters?

A
  1. fetal breathing
  2. gross body movements
  3. fetal tone
  4. AFI
  5. NST
58
Q

In a BPP, fetal breathing should last at least…

A

30 seconds in a 30 minute period.

59
Q

In a BPP, how many gross body movements should be identified?

A

3 episodes

60
Q

In a BPP, how many fetal tone events should be identified?

A

1 episode

61
Q

In a BPP, the AFI should exceed…

A

5 cm

62
Q

In a BPP, the NST should show how many episodes of acceleration?

A

2 episodes

63
Q

What’s an equivocal BPP score?

A

6

64
Q

What’s a normal BPP score?

A

8-10

OB/GYN Scanning (14 decks)

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