Class 12: OB 2nd & 3rd Trimester Flashcards
1
Q
the gestational period in the human usually lasts ___ days, ___ weeks, ___ months
A
280 days, 40 weeks, 9 months
2
Q
weeks of first trimester? significance of first trimester?
A
weeks 1-12; period of organogenesis
3
Q
weeks of 2nd trimester? significance of 2nd tri?
A
weeks 13-26; period of organ development & differentiation
4
Q
weeks of 3rd trimester? significance of 3rd tri?
A
weeks 27-40; fetal growth & weight gain
5
Q
what is embryonic age?
A
embryologists consider the day of conception as the first day of pregnancy
6
Q
what is another name for gestational age?
A
menstrual age
7
Q
what is gestational/menstrual age?
A
the first day of LMP as the 1st day of pregnancy
8
Q
gestational age is ___ weeks more than embryonic age
A
2 weeks
9
Q
3 structures seen in 1st trimester
A
- gestational sac
- yolk sac
- fetal pole with FHM
10
Q
when can the gestational sac be seen by?
A
5 weeks from LMP (TV)
11
Q
when can the yolk sac be seen by?
A
5.5 weeks from LMP (TV)
12
Q
when can the fetal pole be seen by?
A
6 weeks from LMP (TV)
13
Q
when do the amnion & chorion merge by?
A
16-17 weeks
14
Q
the placenta can be seen as crescent echogenic area by ___ weeks
A
7-8 weeks
15
Q
placenta can be clearly visualized by ___ week
A
12th week
16
Q
placenta borders can be identified by ___ week
A
20th week
17
Q
how much does the fetal pole grow each day in 1st trimester?
A
1 mm/day
18
Q
when is the fetus most susceptible to injury?
A
1st tri
19
Q
amniotic fluid volume increases until ___ weeks
A
36-38 weeks
20
Q
US appearance of amniotic fluid in 1st & 2nd tri?
A
anechoic
21
Q
US appearance of amniotic fluid in 3rd tri?
A
may contain small echogenic particles (vernix)
22
Q
5 functions of amniotic fluid
A
- cushions fetus
- allows movement
- prevents adherence of amnion to embryo
- allows symmetrical growth
- maintains constant temp
23
Q
when is most of the amniotic fluid made by the mother?
A
prior to 20 weeks
24
Q
the amount of amniotic fluid is ___ related to ___ function
A
directly; kidney
25
normal lung development depends on the exchange of ___ within the lungs
amniotic fluid
26
severe oligohydramnios may lead to ____ hypoplasia
pulmonary hypoplasia
27
oligohydramnios is idiopathic 60% of the time. T/F?
false -- there is usually a cause
28
what are the most common causes of oligohydramnios (3)
1. PROM
2. IUGR/FGR
3. abnormalities in fetal genituourinary tract (blockage, no renals, no renal function)
29
polyhydramnios is idiopathic 60% of the time. T/F?
true
30
when may the sonographer see amniotic membrane floating in amniotic cavity?
after 16 weeks
31
what can floating amniotic membranes cause?
amniotic band syndrome
32
what is amniotic band syndrome?
bands/tears from amnion may entangle fetal structures and cause defects
33
what is another name for uterine contractions?
braxton hicks contractions
34
what are braxton hicks contractions?
smooth contractions of the myometrium
35
when can braxton hicks contractions occur?
throughout pregnancy
36
how long do uterine contractions occur?
about 30-45 minutes
37
U/S appearance of contractions?
homogenous
38
what is cervical incompetence?
cervical dilation prior to term
39
what is an abnormal endocervical canal length?
< 2.5 cm
40
what is a cerclage?
loop placed in cervix to hold it closed
41
what condition is considered normal in 2nd or 3rd trimester with the maternal kidneys?
some degree of hydronephrosis
42
which kidney is maternal hydronephrosis more common in?
right kidney
43
what does EDC stand for?
estimated date of confinement (due date)
44
how is EDC calculated?
by the 1st day of LMP
45
what 4 measurements are used for dating fetus in US?
BPD, HC, AC, FL
46
what week do the 3 primary brain vesicles start developing? what are these vesicles called?
~ week 6
prosencephalon
mesencephalon
rhombencephalon
47
what cystic structure can be seen in the posterior aspect of the fetus around 6-8 weeks?
rhombencephalon
48
what do the lateral ventricles look like around 11-12 weeks?
butterfly appearance
49
the choroid plexus can be seen at the ____ of the lateral ventricles
roof
50
function of the choroid plexus?
makes CSF
51
what week can the fetal head by well appreciated by?
12th week
52
by what week does the appearance of each brain structure remain relatively the same?
18th week of gestation
53
which plane do we check the contour of the skull bones?
long axis
54
the 4 levels to assess when checking brain development
1. most superior level with IHF
2. forebrain -- lateral ventricles
3. midbrain -- thalamus, CSP, 3rd ventricle
4. hindbrain -- cerebellum, 4th ventricle, nuchal fold
55
another name for interhemispheric fissure
falx cerebri
56
what is the IHF/falx cerebri?
membrane that separates the brain into 2 hemispheres
57
the IHF ensures the separation of the ___ occured
cerebrum
58
the lateral ventricles shouldn't exceed ___ mm or ___ cm
10 mm/1cm
59
which part of the brain is the lateral ventricle a part of?
forebrain
60
where is the widest diameter of the skull?
midbrain
61
3 midbrain landmarks?
1. CSP
2. 3rd ventricles
3. thalami
62
which direction does the apex of the thalami face?
occipital bone
63
where is the CSP located?
midbrain in front of the thalamus
64
where do you take the measurements for BPD & HC?
midbrain at the level of the thalamus, CSP & 3rd ventricle
65
landmarks of the hindbrain?
cerebellum, 4th ventricle, nuchal fold
66
the cerebellum is at the back of the cerebral ___ within the ___ fossa
peduncles; posterior
67
what connects the cerebellar hemispheres?
vermis
68
what is the space in the posterior fossa that is filled with CSF?
cisterna magna
69
a normal cisterna magna may exclude almost all spinal defects. T/F?
true
70
what is the normal measurement of the cisterna magna?
cisterna magna shouldn't exceed 10 mm/1 cm
71
what is the nuchal fold?
skin fold
72
U/S appearance of occipital bone?
echogenic
73
where are the orbits seen seen in comparison to the cerebellar plane?
inferior to cerebellar plane
74
5 routine measurements for dating the fetus?
1. BPD
2. HC
3. AC
4. FL
5. AFI
75
6 nonroutine measurements for dating the fetus?
1. lateral ventricles
2. cisterna magna
3. cerebellum
4. orbits
5. nuchal fold
6. nuchal translucency
76
what does the BPD assess?
gestational age
77
what weeks is the BPD most accurate?
weeks 14-20
78
How to place calipers for the measurements for BPD?
outer to inner
79
landmarks for the BPD?
midbrain: thalamus, CSP, 3rd ventricle
80
what does the HC assess?
gestational age
81
is the HC or BPD more accurate? why?
HC bc it isn't affected by head shape
82
where do you take the measurements for HC?
outer to outer with ellipse or caliper button
83
what are the 2 variations in head shape?
1. brachycephaly
2. dolichocephaly
84
what is brachycephaly?
a more rounded head shape
85
what is dolichocephaly?
more elongated head shape
86
why was the cephalic index (CI) created?
it helps determine a normal fetal head size regardless of variations in fetal head shape
87
formula for CI?
CI = BPD/OFD x 100
88
what is a normal cephalic index range?
75-85%
89
what is considered brachycephaly in regards to the CI?
over 85-90%
90
what is considered dolichocephaly in regards to the CI?
< 70%
91
the cerebellum measurement can be used up to ___ weeks of gestation
24 weeks
92
the cerebellum measurement correlates with fetal ___ from ____ weeks of gestational age
fetal age from 16-24 weeks
93
for the cerebellum measurement, the imaging plane is ___ & ___ to the BPD level
parallel & inferior
94
U/S appearance of cerebellar hemispheres?
2 hypoechoic hemispheres
95
U/S appearance of vermis?
hyperechoic
96
the ___brain is anterior to vermis
midbrain
97
normal measurement of nuchal fold at the level of the cerebellum shouldn't exceed ___
6 mm
98
a nuchal fold measuring 6 mm or more may indicate ___
down's syndrome
99
the lateral ventricles can be clearly identified by which week of gestation?
16th week
100
how do you measure the OFD?
from midpoint of frontal to midpoint of occipital
101
how do you measure the cisterna magna?
from outer of vermis to the inner of occipital bone (ONLY CM)
102
both the NT & nuchal fold rule out ___ abnormalities
chromosomal
103
which trimester is the NT measured in?
1st trimester
104
which plane is NT measured?
sagittal/long axis
105
if the NT is equal to or greater than ___, it can indicate ___ abnromality
3 mm; chromosomal abnormalities
106
which trimester is the nuchal fold measured in?
2nd tri
107
what plane is the nuchal fold measured in?
transverse or cross-section
108
the nuchal fold is measured at the level of the ____
cerebellum
109
how do you measure the nuchal fold?
from outer occipital bone to the outer skin
110
normal measurement for nuchal fold?
less than 6 mm
111
if the nuchal fold measures 6mm or greater, this can indicate what 4 conditions?
1. chromosomal abnl
2. fetal demise
3. skeletal dysplasia
4. fetal hydrops
112
2 measurements for the orbits
1. OOD/binocular distance
2. IOD/interocular distance
113
what does the OOD measure?
gestational age
114
when do you measure OOD?
when unable to get BPD or HC
115
what does IOD rule out?
hyper/hypotelorism
116
best plane to image cleft lip?
sagittal
117
most common fetal neck mass?
cystic hygroma
118
the vertebrae can be well visualized by ___ weeks of gestation
16
119
what is the preferred plane to image the spine? SAG or COR?
SAG
120
how does the spine look on U/S in TRV?
3 highly echogenic ossification centers
121
U/S appearance of the fetal spine in SAG?
railroad sign -- 2 curvilinear lines extending from cervical spine to sacrum
122
U/S appearance of fetal spine in COR?
3 parallel lines that can be imaged from cervical spine to lumbar sacral region
123
define fetal presentation
the fetal part closest to the cervix
124
3 types of fetal presentation
1. cephalic
2. breech
3. other
125
define fetal lie
the long axis orientation of the fetus
126
3 types of fetal lie
1. longitudinal
2. transverse
3. oblique
127
U/S appearance of fetal lungs?
solid masses between fetal heart and ribs
128
U/S appearance of fetal lungs in early fetal life compared to liver?
lungs are iso/hypoechoic to liver
129
U/S appearance of fetal lungs later in fetal life compared to liver
hyperechoic to liver
130
lung maturity is determined by ____
amniocentesis
131
what ratio is checked with amniocentesis to determine lung maturity?
lecithin-sphingomyelin ratio
132
an LS ratio of ___ indicates mature lungs
2+
133
what is the fetal heart rate after the 1st tri?
120-160 BPM
134
what is the most important view for the fetal heart?
4 chamber view
135
what percentage of all abnormalities can be ruled out with the 4th chamber view?
65%
136
the fetal diaphragm can be seen in ___ of fetuses by ___ weeks
1/2 of fetuses by 20 weeks
137
the fetal kidneys are seen by ___ weeks
15-16 weeks
138
the fetal stomach should be documented by ___ weeks
20 weeks
139
U/S appearance of fetal kidneys in early vs later gestation
kidneys are hypoechoic in early gestation & look similar to adult kidneys in later gestation
140
which measurement does fetal weight rely on the most?
AC
141
what is the standard measurement for dating the fetus after 12-15 weeks?
AC
142
landmarks for AC?
stomach
ossification centers of spine
portal sinus
143
how to measure AC?
outer to outer using ellipse
144
how many vessels are in the umbilical cord?
3 -- 1 umbilical vein & 2 spiral arteries
145
which vessel brings oxygen & nutrient rich blood to the fetus?
umbilical vein
146
what do the umbilical arteries do?
carry nutrient poor & O2 poor blood away from fetus to the placenta
147
which trimester is the fetal bowel seen?
3rd tri
148
the fetal urinary bladder can be seen by ___ weeks
20 weeks
149
seeing the UB ensures the ____ of at least ___
presence; 1 kidney
150
how to measure femur length?
measure only diaphysis of bone
151
when is femur length more accurate in dating?
late pregnancy
152
fetal genitalia can be best identified after ___ weeks
20
