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OBGYN 1 > C5.0: 1st Trimester Normal > Flashcards

C5.0: 1st Trimester Normal Flashcards

1
Q

When is the conceptus called an embryo vs fetus?

A

Embryo: from conception to week 10 LMP
Fetus: After week 10

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2
Q

By which time are all structures formed and only need to develop?

A

After week 10

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3
Q

Reasons to do an US in the 1st trim.?

A 
Confirm preg.
Confirm location of preg
Confirm that the size of the embryo matches with the LMP dating
Confirm # of preg.
Confirm viability of preg
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4
Q

what is the only way to confirm the viability of the preg?

A

Demonstrate the fetal heart beat with M mode (not doppler)

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5
Q

How do we confirm that the size of the embryo agree with the dating of LMP?

A

CRL measurement

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6
Q

A preg under how many weeks should have an EV?

A

Under 7 weeks

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7
Q

how long does the ovum live for?

A

12-24 hours

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8
Q

What is a normal sperm count and what is considered sterile? Approx. how long do sperm live?

A

100 million per ml is normal
20 million or less per ml is sterile
Live for approx. 24 hrs and up to 72 hrs

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9
Q

By what process are sperm and eggs produces?

A

Meiosis

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10
Q

How many sperm are produced by meiosis, and how many eggs?

A

4 sperm

1 egg

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11
Q

When does the 2nd meiotic division of the ovum occur?

A

After fertilization

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12
Q

How many autosomes are contributed by each parent?

And how many sex chromosome?

A

22 auto from each

1 sex chromo from each

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13
Q

Which sex chromosome does the mom always give?

A

X

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14
Q

when specifically does the Corona Radiata nourish the egg?

A

Before implantation

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15
Q

What happens to the sperm during fertilization?

A

It penetrates the zone pellucida and it drops its tail and the head enlarges to become the male pronucleus

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16
Q

What happens to the egg immediately after fertilization?

A

It undergoes its second meiotic division to become the female pronucleus

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17
Q

What occurs after the 2 pronuclei are formed?

A

They fuse and the chromosomes mix

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18
Q

What is a zygote? And whats another term for it?

A

The union of sperm and egg

Also called conceptus

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19
Q

What is a Morula?

A

A cluster of cells that undergo cell division but the morula doesnt get any larger…. the cells just become smaller with each division

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20
Q

When does a morula become a blastocyst? and when does the blastocyst enter the uterus?

A

When fluid penetrates the zone pellucida and enters the morula forming a fluid filled cavity
5-7 days after fertilization

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21
Q

When is implantation complete?

A

~day 11-12 post ovulation

~day 9-10 post fertilization

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22
Q

Where does the blastocyst usually implant?

A

On the posterior fundal wall

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23
Q

What is cleavage?

A

Rapid cell division without a change in size of the zygote

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24
Q

After the first cleavage division, what are the two daughter cells called?

A

Blastomeres

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25
Q

At what number of cells is the zygote called a morula?

A

12-16 blastomeres

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26
Q

What are the 2 types of cells in the blastocyst?

A

1) Trophoblast (outer layer)

2) Embryoblast (inner layer)

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27
Q

What does the trophoblast form and what is its function?

A

Placenta and chorion

Function is to gain access to maternal circulation

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28
Q

What does the embryoblast form?

A

The embryo, yolk sac and amnion

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29
Q

What must happen to the zone pellucida before implantation?

A

It must disappear

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30
Q

The trophoblast separates into which 2 layers?

A

1) Syncytiotrophoblast

2) Cytotrophoblast

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31
Q

Function of the Syncytiotrophoblast

A

Produces hCG

Erodes the endometrial stroma so the blastocyst can sink in and forms lacunae in the stroma

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32
Q

What do the lacunae eventually become?

A

The intervillous spaces of the placenta

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33
Q

What does the cytotrophoblast produce?

A

Primary chorionic villi which project into the lacunae

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34
Q

what are the 2 types of primary chorionic villi?

A

Chorion Frondosum

Smooth chorion/Chorion Laeve

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35
Q

Chorion Frondosum

A

the villi directly at the implantation site… form the early placenta

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36
Q

Smooth chorion/Chorion Laeve

A

all remaining villi around the gestational sac

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37
Q

Which two samples can be analyzed for chromosomal abnormalities?

A

Amniotic fluid

Chorionic villi

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38
Q

What is the decidua reaction?

A

When the decidua cells of the endometrium increase in size to prepare for implantation (caused by hCG and progesterone)

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39
Q

What causes a pseudo-sac to form in the uterus?

A

An ectopic pregnancy because it triggers the same decidua reaction of the endometrium as an intrauterine preg.

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40
Q

With a pregnancy in a bicornuate uterus, what happens to the non pregnancy horn?

A

The decidua reaction will occur in the non preg horn (pseudo-sac formed) and it will make it look like a twin preg

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41
Q

What is the acronym to remember the decidua layers of the uterus? And what are the layers?

A

BCP (birth control didnt work in this instance)

1) Decidua basalis
2) decidua capsularis
3) decidua parietalis (or vera)

42
Q

what is the location of each of the decidua layers?

A

Basalis: the area underlying the conceptus (will becomes the maternal side of the placenta)

Capsularis: part that covers the gestational sac

parietalis: all remaning decidua

43
Q

What is the double decidual sign?

A

When you can see the layers of the perietalis and the capsularis on US….. rules out a pseudogestational sac before the embryo can be seen

44
Q

Which layers of a decidua fuse?

A

The vera/parietalis and the capsularis

45
Q

what can occur when these layers fuse?

A

Blood can accumulate in the potential space between these two layers and mimic a twin preg.

46
Q

Which yolk sac do we see on US?

A

2ndary yolk sac

47
Q

What is the amnionic cavity and when does it form?

A

a small space between the inner cell mass and the trophoblast
forms by day 9

48
Q

Once the amniotic cavity is formed, what is the blastocyst cavity called?

A

The primitive yolk sac

49
Q

whats the double bleb sign and when is it seen?

A

Represents the early amnion and yolk sac

Seen around 5.5 weeks on EV ONLY

50
Q

When do the amnion and chorion fuse?

A

week 16

51
Q

When does the embryoblast/inner cell mass become the bilaminar disk?

A

4 weeks LMP

52
Q

2 layers of the bilaminar disc

A

1) epiblast

2) hypoblast

53
Q

What does the epiblast form?

A

gives rises to almost all cells in the embryo and forms the amniotic membrane

54
Q

What does the hypoblast form?

A

helps form the primitive ectoderm

55
Q

What is gastrulation and when does it occur?

A

The formation of the three layers of the trilaminar disk

5 weeks LMP

56
Q

What are the layers of the trilaminar disk and in what order do they differentiate?

A

Endoderm (inner): 1st
Mesoderm (middle): 3rd
Ectoderm (outer): 2nd

57
Q

What do each of the layers of the trilaminar disk form?

A

endoderm: Lining of the GI and respiratory tract
mesoderm: forms muscles, bone, urogenital tract
Ectoderm: hair, skin, teeth, nails and CNS

58
Q

What is neurulation and when does neurulation occur?

A

The formation of the neural plate, neural folds and neural tube
begins at week 3 after conception or 5 weeks LMP

59
Q

When and how does the neural tube close?

A

~40 days LMP, it starts to close in the middle and then progresses outwards

60
Q

Ancephaly and spinal bifida occur when which areas of the neural tube dont close?

A

Ancephaly: Cephalic end doesnt close

Spinal Bifida: Caudal end doesnt close

61
Q

what parts of the fetus make up the yolk sac?

A

the head and tail which fold in to make up part of the sac

62
Q

when is the yolk sac seen on US?

A

from 5 weeks until week 10 or 12

63
Q

Function of the yolk sac

A

Provide nutrients before circulation
Begins the development of hematopoiesis
Forms the digestive tract
Forms the sex glands

64
Q

What is the allantois and what does it form?

A

a pouch of the yolk sac

forms the umbilical vessels and the bladder

65
Q

how much does the gestational sac and the embryo grow each day?

A

~1.1mm for gest. sac

~1-2 mm up until 8 weeks

66
Q

whats the upper limit of normal for the yolk sac before 10 weeks?

A

6mm (measured inner to inner well)

67
Q

what is the mean sac diameter of the gest. sac for 6, 7 and 8 weeks?

A

6: 15 mm
7: 20 mm
8: 30 mm

(L+ W+D/3)

68
Q

when do you measure the gestation sac?

A

when you dont see an embryo

69
Q

What are the gest. sac measurements with EV scanning for weeks 4 and 5? and the yolk sac meas. for 5. weeks?

A

4: 2-3 mm
5: Gest: 5-6mm
Yolk: 2-3 mm

70
Q

What is the CRL at 6 and 7 weeks with EV scanning?

A

6: 3-4 mm
7: 12-14 mm

71
Q

what are the two types of pregnancy tests and which is qualitative/quantitative?

A

Urine (qualitative)

Blood (quantitative)

72
Q

When can a urine test detect pregnancy and what are some draw backs of this test?

A

at 4 weeks LMP
problems:
must meet threshold to be positive
negative result doesnt exclude pregnancy

73
Q

how does a blood test detect preg.?

A

tests the beta sub unit of hCG

74
Q

at what date LMP will a blood test detect a pregnancy?

A

23 days

75
Q

when does hCG plateau?

A

8 weeks

76
Q

what are the different units for Beta hCG?

A

1st international reference preparation (FIRP)
2nd international standard (OLDEST) (SIS)
3rd international standard (TIS same values as FIRP)

77
Q

when should an ectopic pregnancy be considered (with reference to hCG)?

A

if theres no IUP and hCG is at or greater than the discriminatory zone

78
Q

whats the discriminatory zone?

A

500-1000 mlU/ml 2nd IS
or
1000-2000 mlU/ml IRP

FOR EV SACNNING ONLY

79
Q

when should fetal heart motion be detected?

A

if CRL of embryo is >5 mm by EV

day 23

80
Q

B hCG levels double how often?

A

every 2 days until 8 weeks gestation

81
Q

how does ectopic preg. effect B hCG level?

A

the B hCG levels may not quite double every 2 days…. it could be slightly less, or the same as a normal preg.

82
Q

what do high levels of B hCG indicate?

A 
twins
hydatitiform moles (more genetic material that norm)
tumor of the chorion, ovary, or the fetus
83
Q

what do low levels of B hCG indicate?

A

ectopic preg
fetal death
inaccurate dating (can also cause high levels of hCG)

84
Q

what is pseudocyesis?

A

when a women thinks and feels like she’s pregnant

85
Q

whats the 1sr trim. OB protocal

A
  • ‘female pelvis’
  • MSD if no embryo… if embryo, measure CRL 3 times (look in trans to find longest length)
  • measure and document yolk sac
  • m mode heart rate
86
Q

what is the vitelline vessel?

A

it connects the yolk sac to the embryo

87
Q

when do you do both an CRL and a BPD measurement?

A

if the fetus is 12-14 weeks

88
Q

Is the yolk sac located in the amniotic cavity?

A

No

89
Q

Can the amnion be visualized on US if there’s no embryo seen?

A

Yes

90
Q

What is rhombencephalon?

A

the hindbrain of the embryo…. seen only in the 1st trimester.
A cystic structure in the posterior fossa

91
Q

In week 8 the midgut herniated into the umbilical cord causing a protrusion of the fetal abdomen, what is this called?

A

Physiological midgut herniation

92
Q

How long does it take the egg to reach the ampulla portion of the Fallopian tube?

A

24-36 hrs

92
Q

What forms the fetal part of the placenta?

A

Chorion

93
Q

What’s another name for the bilaminar disk

A

Embryonic disk

94
Q

The CRL measurement is very accurate for dating of the preganancy up to how many weeks?

A

12

95
Q

Crown rump measurements are accruate to +/- how many days?

A

3

97
Q

The yolk sac can often be seen on an EV ultrasound when the MSD is how many mm?

A

8

97
Q

The yolk sac is often seen by a transabdominal ultrasound when the MSD measures how many mm?

A

20

98
Q

The embryo can often be seen on an EV ultrasound when the MSD measures how many MM?

A

16

99
Q

Does the embryonic pole develop in close proximity to the chorion frondosum?

A

Yes

101
Q

The embryo is readily visualized on a transabdominal ultrasound when the MSD measures how many mm?

A

25

102
Q

after how many wks can a fetal heart beat definitely be detected on EV

A

after 6

OBGYN 1 (24 decks)

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