OBS imaging Flashcards

1
Q

What is the most accurate way of dating a pregnancy?

A

CRL between 7 -12 weeks

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2
Q

What is the accuracy of CRL to predict the date of delivery?

A

+/- 5 days

+/- 3-8 days in another guideline

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3
Q

Why is accurate dating of pregnancies important (4)?

A

Decreases # of IOL

Helps in scheduling CS

Assessment of fetal growth

Better accuracy of aneuploidy screen

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4
Q

Of parameters for EFW in the second trimester, which is the most accurate?

Which has the most variation?

A

Most accurate: Head circumference

Most variation: Abdo circumference

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5
Q

What is the incidence of ectopic pregnancies ?

What is the % of fetal death related to ectopic pregnancies?

A

Incidence 1%

Maternal death 4%

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6
Q

At how many weeks can midgut herniation be considered abnormal

A

12 weeks

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7
Q

What is the highest value normal value of NT at 11-14 weeks?

What size should be the CRL to use the NT?

A

3.5 mm

45 - 84 mm

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8
Q

What is increased NT related to?

A

Trisomy 13, 18, 21

Chromosomal or developmental abnormalities

Genetic syndroms

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9
Q

What are the parameters of the algorithm to predict maternal PET?

A

Maternal clinical factors

MAP

Bilateral uterine artery pulsatility index

PAPPA

Placental growth factor

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10
Q

What are US findings suggestive of early pregnancy loss (4)?

A

Bradycardia (< 85 bpm) > 7 weeks

Small sac relative to the embryo (GS - CRL < 5 mm)

Enlarged or abnormal yolk sac (> 5-6 mm)

Subchorionic hematoma

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11
Q

What is the single most useful test to differentiate a viable from a non-viable pregnancy?

A

Progesterone level

< 20 nmol

Sensitivity 75 %, specificity 98% for failed pregnancy

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12
Q

What is the single most useful test to differentiate an IUP from an ectopic?

A

US

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13
Q

What are the US criteria to diagnose an arrested pregnancy?

A

CRL >/= 7 mm and no FHR

Empty GS with GSD >/= 25 mm

No cardiac activity 2 weeks after an US showing a GS without a yolk sac

No cardiac activity 11 days after an US showing a GS with a yolk sac

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14
Q

What is the first test to do in a patient with suspected ectopic?

A

serum beta hCG!

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15
Q

What is the time frame of the gestational period?

A

8 weeks after conception

10 weeks after LMP

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16
Q

What is the incidence of heterotopic pregnancies in spontaneous and ART pregnancies?

A

Spontaneous: 1/7000 - 1/30 000

ART: up to 1%

17
Q

What are the minimum requirements to diagnose an IUP on US?

A

Intra uterine GS + (embryo or yolk sac)

18
Q

What is the most common location of ectopic pregnancies?

A

1 - Ampulla (70%)

2- Isthmic (12%)

3- Fimbria (11%)

4- Ovarian (3%)

5- Interstitial / cornual (2-3%)

6- Abdominal (1%)

7- Cervical (<1%)

19
Q

What is the minimal rise in beta-hCG in viable pregnancies?

A

55% in 48h

(1.4 - 2.1) in 48h

20
Q

When does beta hCG first become positive?

A

21 -22 days after LMP

8 days after ovulation

= Start of implantation

21
Q

What is the time frame of the gestational period?

A

8 weeks after conception

10 weeks after LMP

22
Q

When does the amnio fuse to the chorion?

A

12 - 16 weeks of gestation

23
Q

Describe the variations in FHR between 5-10 wks

A

5.5 - 6.5 weeks < 100 bpm

7-10 wks - up to 180 bpm

24
Q

How long does sperm survive?

A

5-7 days

25
Q

When can you first hear FHR by doptone?

A

11 -12 weeks

26
Q

When should the CRL be used (in mm) to date a pregnancy?

A

Between 10 - 84 mm

10 mm = 7 weeks

27
Q

Between how many weeks gestation are CRL and BPD equivalent?

A

12 - 14 weeks

28
Q

What is the definition of dolichocephaly

A

Head longer than expected

29
Q

What is the definition of brachycephaly

A

Skull shorter than expected

30
Q

What is achodroplasia?

A

Prevents ossification of long bones.

Dwarfism

Scoliosis

Macrocephaly

31
Q

What parameter of biometry correlates better with GA?

A

HC

32
Q

Which biometry parameter has the most variation?

A

AC

33
Q

What are some advantages of doing a dating US

A
  • Improve MMS accuracy
  • Identification of gross anomalies
  • Identification of twin gestations
  • NT
  • DEcrease post date inductions