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OB > Normal 1st Trimester > Flashcards

Normal 1st Trimester Flashcards

1
Q

Prenatal definition

A

from conception to birth

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2
Q

menstrual age

A

aka gestational age

length of pregnancy determined by first day of last menstrual period

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3
Q

embryonic age

A

aka conceptual age
age at conception
gestational age adds two week to conceptual age

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4
Q

embryo

A

implantation until 8 (10 gestation) weeks

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5
Q

fetus

A

after 8 (10) weeks

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6
Q

infant

A

between birth and one year of age

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7
Q

previable

A

infant delivered prior to 24 weeks

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8
Q

preterm

A

infant delivered between 24-37 weeks

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9
Q

term

A

infant delivered between 37-42 weeks

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10
Q

posterm

A

infant delivered after 42 weeks

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11
Q

Pregnancy is divided into…

A

trimesters:
1st until 12 weeks (14 gestational)
2nd from 12(14) to 24(26)
3rd from 24 to delivery

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12
Q

What is the difference between menstrual age and embryonic age?

A

Menstrual age is the length of pregnancy determined by the first day of the last menstrual period. Embryonic age is the age of the fetus at conception; it is two weeks less than the menstrual age.

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13
Q

Describe the early progression of pregnancy.

A 
Day 1: zygote divides into two cells
Day 2: zygotes divides into four cells
Day 3?: zygote becomes a 16 cell morula
Day 4-5: blastocyst enters uterus
Day ~7: implantation begins 
Day 12: implantation is completed
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14
Q

What is a morula?

A

ball of cells

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15
Q

What is a blastocyst made up of?

A

made up of trophoblast (secretes hCG) and inner cell mass(ICM)

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16
Q

What does the trophoblast develop into?

A

the placenta

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17
Q

What does the ICM develop into?

A

the embryo and portion of placenta

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18
Q

What causes the endometrium to have a decidua reaction?

A

the trophoblastic cells secrete hCG that is absorbed within the tubes and stimulates maternal pregnancy responses;
hCG causes the uterine endometrium to convert to decidua

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19
Q

What two layers make up the trophoblast?

A

the outer layer is syncytiotrophoblast and the inner layer is the cytotrophoblast

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20
Q

What does the syncytiotrophoblast do?

A

invades endometrium and breaks down glands and blood vessels. The nutrients from the glands will provide nourishment for the embryo.

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21
Q

Fertilization…

A

formation of zygote (46 chromosomes)

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22
Q

Following implantation, what happens to the ICM?

A

it matures into the embryonic disk, future embryo, and the primary yolk sac

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23
Q

What is a decidua?

A

a glycogen-rich mucosa that nourishes the early pregnancy

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24
Q

What are the locations of each decidua?

A

decidua basalis: under blastocyst (occurs between blastocyst and myometrium)
decidua capsularis: above blastocyst (occuring over blastocyst closest to endometrial cavity)
decidua parietalis: reaction except for areas beneath and above implanted

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25
Q

What does the decidua reaction look like sonographically?

A

echogenic

can see double decidual sac sign

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26
Q

What is the decidual sac sign?

A

echogenic decidua capsularis, hypoechoic uterine cavity, and echogenic decidua parietalis
Sign of intrauterine pregnancy , typically fundal location noted

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27
Q

When is the secondary yolk sac formed and how?

A

23 gestational days; primary yolk sac is pinched off by extraembryonic coelm and forms secondary yolk sac, which is between the amniotic and chorionic cavities

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28
Q

Which yoke sac is seen sonographically?

A

secondary yolk sac

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29
Q

zygote

A

first 12 days after conception

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30
Q

What is gastrulation?

A

development of germ layers

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31
Q

What are the germ layers?

A

ectoderm, mesoderm, and endoderm

all give rise to future human tissues

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32
Q

When does organogenesis take place?

A

between day 14 and 60 (2/3 - 8 weeks)

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33
Q

When does gastrulation take place?

A

during the 5th gestational week

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34
Q

What happens during gastrulation?

A

single layered blastula is reorganized into a trilaminar gastrula (three germ layers)

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35
Q

By the endo of the 10th week, what does the CRL of the fetus measure?

A

35mm; embryo develops C-shaped structure and human-like appearance

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36
Q

When is the fetal anatomy fully developed?

A

in late first trimester

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37
Q

When can an intrauterine pregnancy be visualized sonographically and what can be seen?

A

during the 5th gestational week;

1-2mm gestational sac with echogenic ring having sonolucent center (chorionic cavity)

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38
Q

Sonographically describe the gestational sac.

A

round/oval, fundal/middle portion of uterus/eccentrically placed position in middle portion of uterus, smooth, echogenic, 3mm or more in wall thickness;
secondary yolk sac present when MSD >10mm, embryo present when MSD >18mm;
grows 1mm per day

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39
Q

When should the amniotic cavity/membrane, chorionic cavity, yolk sac, and embryo be visualized?

A

between 5.5 and 6th gestational week

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40
Q

What does the number of yolk sacs indicate?

A

the number of amnions

41
Q

When is the yolk sac routinely visualized?

A

between 5 and 5.5 gestational week

42
Q

What are the functions of the secondary yolk sac?

A

to provide nutrients to developing embryo, hematopoiesis, development of embryonic endoderm (forms primitive gut)

43
Q

When does the secondary yolk sac detach from the yolk stalk?

A

~8 weeks gestation, due to amniotic cavity expansion

44
Q

What predicts a viable pregnancy?

A

visualization of the yolk sac;

>90% of cases

45
Q

The yolk sac diameter should not exceed…

A

6mm; enlarged yolk sac is not a good sign

46
Q

In twin pregnancies, one yolk sac signifies…

A

monochorionic, monoamniotic pregnancy

47
Q

In twin pregnancies, two yolk sacs signify…

A

diamniotic, monochorionic or

diamniotic, dichorionic pregnancy

48
Q

When is the secondary yolk sac no longer visualized?

A

by 12th week

49
Q

When is heart motion detected in the embryo?

A

at 5.5 weeks

when CRL is 3mm

50
Q

When must the embryonic heartbeat be seen?

A

when the CRL is greater than 4mm

51
Q

When is the amniotic membrane visualized?

A

after 5.5 weeks

52
Q

Describe the chorionic cavity.

A

fluid is more dense than amniotic cavity. Waste products are disposed here and can have echogenic materials

53
Q

What can a sonographer do to appreciate the difference in the chorionic and amniotic cavity?

A

increase the gain

54
Q

When does chorioamniotic fusion take place?

A

12 weeks

55
Q

How is the yolk stalk created?

A

when constriction/narrowing between the embryo and yolk sac takes place (due to formation of embryonic head, caudal portions, and lateral folds)

56
Q

When is the embryonic period?

A

time between 4 and 10 weeks of gestation

57
Q

When can the developing spine be visualized?

A

at 6 weeks of gestation; parallel echogenic lines with a sonolucent center

58
Q

When does the neural tube close?

A

around the 6th gestational week (4th embryologic week)

59
Q

By 8 weeks gestation, what primary vesicles are seen within the fetal brain?

A

prosencephalon (telencephalon and diencephalon), mesencephalon, and the rhombencephalon
they appear as three anechoic portions in the embryo head

60
Q

What does each vesicle give rise to?

A

telencephalon: cerebrum and retina of eyes
diencephalon: thalamus, hypothalamus, epithalamus
mesencephalon: midbrain
rhombencephalon: brain stem (medulla oblongata, pons), cerebellum

61
Q

What two segments does the rhombencephalon divide into?

A

metencephalon (cephalic) and myelencephalon (caudal)

62
Q

What can be seen in the embryonic cranium at 8-10 weeks gestation?

A

cystic rhomboid fossa, posterior aspect of embryonic cranium

63
Q

What can be seen at 9 weeks gestation in the embryonic cranium?

A

cerebral hemispheres, midline falx, echogenic choroid plexus tissue in lateral ventricles

64
Q

What can be seen at 10 weeks gestation in the embryonic cranium?

A

choroid plexus (echogenic in anechoic ventricles) and lateral ventricles occupy entire cranial vault, fourth ventricle

65
Q

If the yolk sac is seen, what age should the embryo be?

A

less than 12 weeks gestation

66
Q

When are limb buds recognizable via sonography?

A

during 7th gestational week, but not identified until calcification of long bones at 10 weeks
upper limbs form first, followed by lower limbs
develop proximal to distal

67
Q

When are the hands and feet completely formed?

A

by end of 10 gestational week

fingers form earlier than toes

68
Q

What begins calcification at 8 weeks gestation?

A

clavicle; followed by mandible, palate, vertebral column, neural arches

69
Q

When do frontal cranial bones begin calcify?

A

at 9 weeks, followed by long bones

70
Q

By what week does the maxilla and mandible appear as brightly echogenic structures?

A

week 9

71
Q

When is the anterior abdominal wall developed?

A

by 6th gestational week

72
Q

Describe the herniation of bowel.

A

as amniotic expansion occurs, midgut elongates faster than embryo growing, causing midgut to herniate into base of umbilical cord

73
Q

When does the midgut descend into the fetal abdomen?

A

at 11th week

74
Q

After __ week of gestation, echogenic umbilical cord mass no longer visualized and echogenic bowel seen within fetal abdomen.

A

12

75
Q

What is the first organ to function within the embryo?

A

the heart

76
Q

When does the heart start beating?

A

at 35 days (5-5.5 weeks)

77
Q

When has the heart obtained adult configuration?

A

end of 8th week gestation

78
Q

When should (ALWAYS) embryonic heart be seen by?

A

by 46 menstrual days or when CRL >4mm

79
Q

What are the normal fetal heart rates?

A

6 weeks: 90-115 bpm
9 weeks: 140-160 bpm
remainder of 1st and 2nd tri: 140 bpm

80
Q

What is the most accurate measurement for sonographic gestational dating?

A

CRL (until fetus starts to curl at 12 weeks)

81
Q

How do you calculated the mean sac diameter?

A

length x width x height /3

82
Q

How do you calculate the menstrual age in days with the MSD?

A

MSD+30

83
Q

How do you calculate the menstrual age in weeks with the menstrual age in days?

A

menstrual age (days) / 7

84
Q

How early can the CRL be obtained?

A

5.5 weeks using transvaginal US

85
Q

What is used to assess 1st trimester risk?

A

amniocentesis, triple screen, chorionic villi sampling, nuchal translucency measurement

86
Q

Overall, twin gestations have __ to __ times greater mortality rate than do singletons

A

7 to 10

risk increasing when twins are monozygotic (sharing placenta)

87
Q

Multiple gestation is a ___ risk pregnancy; highest and lowest in what populations?

A

high
lowest in asian population
highest in African population

88
Q

When the cell splits between days 1 and 3, what develops?

A

identical twins; dichorionic/diamniotic

with two different placentas

89
Q

When the cell splits between days 4 and 8, what develops?

A

monochorionic/diamniotic

90
Q

When the cell splits between days 8 and 13, what develops?

A 
monochorionic/monoamniotic
momo twins (sharing placenta)
91
Q

There are twins of different genders, how many chorion and amnions?

A

dichorionic

dizygotic - different placentas

92
Q

What does the twin peak sign indicate?

A

dichorionic/diamniotic; two placentas

93
Q

How does the twin peak sign look sonographically?

A

echogenic placental villi; four layers between embryos (amnion, chorion, chorion, amnion)

94
Q

What does the t sign indicate?

A

monochorionic; single placenta

95
Q

How does the t sign look sonographically?

A

one chorion and two amnion

echogenic amnionic membrane between fetus

96
Q

For monochorionic/diamniotic twins, when does the cell split?

A

between days 4 and 8

97
Q

For dichorionic/diamniotic twins, when does the cell split?

A

between days 1 and 3

98
Q

For momo twins, when does the cell split?

A

between days 8 and 13

99
Q

The number of chorions indicates the number of what?

A

placentas

OB (10 decks)

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