Test 2 Flashcards
what is the AIUM statement?
fetal ultrasound should be preformed only when there is a valid medical reason, and the lowest possible ultrasonic exposure settings should be used to hain the necessary diagnostic info
what is the principle of prudent scanning?
ALARA
what do bioeffecrs depend on?
intensity of the beam, the duration of exposure, as well as frequency
where is thermal bioeffects?
ultrasound travels through tissue, energy is absorbed by the tissue components and coverted to heat
increased heat is considered a potential ________
teratogen
what does thermal bio effects do?
- affects the rate of chemical reactions
- alters the equilibrium between chemical reactions
what is a non thermal bio effect?
caviation
gas bubbles
what is caviation?
the expansion and contraction or collapse of gas bubbles during the oscillatory cycle
what does damage tissues containing gas do?
- potentially pertains to the neonate
- lung, inestine
what is thermal index?
a thermal index of one (TI 1) indicates conditions under which the rise in temperature would likely by 1C
what is the threshold in thermal index before any evidence of development effect occurs?
1.5 to 2C
what is considered potentially hazardous in thermal index?
diagnostic exposure that elevates embryonic and fetal in situ temperature above 41C for 5 minutes should be considered potentially hazardous
Routine grey scale ultrasound in the 1st trimester is __________ to have adverse effects.
unlikely
what is the rise in temperature with modern ultrasound systems?
usually less than 1C
what may cause a rise in temperature of more than 1.5C in the first trimester?
Doppler US for fetal heart rate when used for more than 30 seconds
what does teratogenic mean?
able to disturb the growth and development of an embryp or fetus
what can produce teratogenic effects?
elevated maternal temperature whether from illness or exposure to heat
for all OB sonograms obtained before 8 weeks what should the TI setting be set to?
soft tissue (TI’s)
for all OB tests preformed after 8 weeks what should the TI setting be set to?
bone (TIb)
what should the power not be set to ever for an OB study?
never be near 100%
what is mechanical index?
describes the potential for mechanical bio-effects (caviation, gas bubbles) to occur
what can mechanical index be used to estimate?
for the degree of bio-effects a given set of ultrasound parameters will induce
a higher mechanicnal index means a higher ___________
bio effect
what MI should US scanners not exceed?
1.9
what are fetal sonographic examinations?
- first trimester
- standard second or third trimester
- limited examination
- specialized examination (level 2, targeted exam)
describe specialized examination?
- detailed anatomic examination
- preformed when an anomaly is suspected
- indicated by fam history
- biochemical abnormalities
- indicated by the results of a standard examination
what does a standard OB sonogram in the 1st trimester include?
- evaluation of the presence, size, location, and number of gest. sacs
- the gestational sac is examined for the presence of a yolk sac and embryo
- measure embryo/fetus and cardiac activity
what should be examined in first trimester imaging?
- uterus
- cervix
- adnexa
- cul-de-sac
what does a standard OB sonogram in the 2nd or 3rd trimester include an evaulation of?
- fetal presentation
- amniotic fluid volume
- cardiac activity
- placental position
- fetal biometry
- fetal number
- anatomic survey
what should be examined in the 2nd/3rd trimester when technically feasible?
maternal cervix and adnexa
what does lower freq provide?
more penetraton
what does higher freq provide?
better resolution
what do transvaginal transducers allow for?
superior resolution while still allowing adequate penetration
how often should instrumentation used for diagnostic testing be maintained in good operating condition and undergo routine calibration?
at least once a year (annually)
what routine inspection and testing must be done in all existing equipment?
testing for electrical safety
who must request for the examination?
must be originated by a physician or other appropriately licensed health care provider or under the providers direction
what should thier be a permanent record of?
ultrasound examination and its interpretation
what images must be obtained?
all appropriate areas, both normal and abnormal
what should images be labeled with?
- patient ID
- facility ID
- exam date
- side (right or left)
what should be obtained in the patients medical record?
an official interpretation (final report) of the ultrasound findings
retention of the US examination should be consistent with both what?
clinical needs and with relevant legal and local health care facility requirements
what are some causes of uncertain LMP?
- poor menstrual history
- amenorrhea
- prolonged or short cycle-not every 28 days
- DUB
- recent miscarriage
with advances in prenatal testing, pregnancy is now known to have a duration of how long?
280 days from the first day of the LMP, also referred to as 9 calendar or 10 lunar months
in clinical practice, the term gestational age is often used interchangeably with what?
menstrual age
what is needed to manage the pregnancy optimally?
the knowledge of an acurate gestational age
what is the biometry measurments of the 1st trimester?
- gestational sac (mean sac diameter)
- crown rump length
what are the additional measurments in the 1st trimester?
- yolk sac (2-6mm)
- nuchal translucency (<3mm between 11 and 14 weeks)
what is the 1st sonographic evidence of an intrauterine pregnancy?
gestational sac
what is a gestational sac?
anechoic fluid collection surrounded by an echgenic ring in the fundal region of the endometrial cavity
what is a vital structure of a normal pregnancy and what is it made of?
echogenic ring=chorionic and decidua capsularis
what does absence of the echogenic ring prompt?
suspicion of a pseudogestational sac associated with ectopic pregnancy
how is the mean sac diameter (MSD) calculated?
measurement of gestational sac in all 3 dimentions
-made at the interface between the echogenic border and the fluid
what is the gestational sac surrounded by?
decidualised endometrium
with transvaginal technique how will a pregnancy 4 weeks and 1 or 2 days from LMP be visualized?
2-3 mm fluid collection within the uterus
what should MSD correlate with?
suspected gestational age
how fast does gestational sac grow?
approx 1mm per day
evidence of developing intrauterine pregnancy should be seen transvaginally with a serum beta-hCG level greater than what?
1000-2000 mIU/mL
what standard is used in the beta-hCG?
international reference preparation
describe alpha fetaprotein (AFP)?
- produced by the fetus
- found in the amniotic fluid and maternal serum
- normal values vary with gestational age
what may cause high values of AFP?
- underestimated gest. age
- fetus older than expected
- multiple gestations
- open neural tube defect
- abdominal wall defect
- cystic hygroma
- renal anomalies
- fetal demise
what may cause low levels of AFP?
- overestimated gestational age
- fetus younger than expected
- chromosomal abnormalities
- trophoblastic disease
- long-standing fetal demise
- chronic maternal hypertension
- diabetis
with TVS, gestational sac measuring _____ should demonstrate a yolk sac
< 8mm
yolk sac measuring 8mm should be consistent with what?
5-5.5 week gestation
what does the yolk sac do?
supplies nutrition for the developing embryo through the vitelline duct
how can the yolk sac be seen?
yolk sac and embryo can be seen seperated by the echogenic amnion but connected by the vitelline duct
what should the size of the yolk sac be in the first trimester?
2-6 mm
what is an abmornally sized yolk sac indicative of?
pending loss or fetal abnormality
how should the yolk sac be measured?
with placement of calipers along the inner borders of the echogenic ring (AP)
what does the yolk sac assist in?
locating the developing embryo and possible cardac acitivity
what is associated with a poor prognosis with the yolk sac?
- size
- shape
- echogenicity of the yolk sac
how long is the embryonic period?
week 6 through week 10 of pregnancy
what rate does the embryo grow?
1mm per day
how does the embryo appear?
flat, disc like structure
when may the heart beat be found in the embryo?
5.5 weeks or when the CRL measures 5mm
when should the embryo be visualized in a gestational sac with transabdominal?
gestational sac measures 25mm
what is the normal embryonic heart rate?
120-180 beats per minute
what should be done when the embryonic heart rate is 100 beats or less?
it should be compared with the maternal heart rate to ensure that maternal uterine vessels are not being samples and inaccurately represented as embryonic cardiac activity
when does the embryo begin to assume a C-shaped appearance?
by about 8 weeks
if there is more than one first trimester scan with a mean sac diameter or crown-rump length measurment what should be used to determine gestational age?
the earliest ultrasound with a crown rump length equivalent to atleast 7 weeks (or 10mm) should be used to determine gestatinal age
when is the distinction between the head and torso of the fetus easily recognized?
around 11-12 weeks
how is an accurate CRL measurement taken?
placement of the calipers at the top of the fetal head (crown) to the bottom of the torso (rump)
when do we avoid using CRL measurment?
when the embryo is flexed
what measurement is used as a early screening tool for possible fetal aneuploidy?
nuchal translucency
what is an increased NT thickness associated with?
- genetic syndromes
- structural anomalies
- adverse outcome
what must be assessed before the NT measurment is used?
gestatinal age with CRL
what CRL can a NT be evaluated?
CRL no less than 45 mm and no more than 84mm
what gestional ages are CRL 45mm and 84mm?
11 and 13+6 weeks
when is the NT considered thickened?
3mm or more
what plane is used when measureing NT?
sagital plane
what is the sonographers role in early pregnancy?
viability
when can diagnosis of embryonic dealth be made?
if CRL measures 5mm and cardiac activity is not seen
what may lead to pregnancy loss in 1st trimester?
subchorionic hemorrhage
what are subchorionic hemorrhages?
low pressure hemorrhages that occur most commonly in the 1st trimester of pregnancy
how do subchorionic hemorrhages result?
result from implantation of the fertlized ovum into the uterus
what distinguishes subchorionic hemorrhage from abruption placentae?
hemorrhage is seen between the uterine wall and the membranes and are not associated with the placenta
what may subchorionic hemorrhage lead to?
may spontaneously regress or may leas to spontaneous abortion
where does hemorrhage have a better prognosis?
better in the lower segment than at the uterine fundus
what patients with subchorionic hemorrhage have a higher incidence of pregnancy loss?
patients who present with bleeding
what can help differentiate a hematoma from a neoplasm?
hematoma will have a lack of vascularity
what is a threatened abortion?
characterized by bleeding without cervical dilation
what is a missed abortion?
characterized as embryonic death without expulsion of the products of conception
what is a complete abortion?
when there is expulsion of the products of conception
when does SAB (abortion) rate decrease dramatically?
when the pregnancy reaches 12 weeks
what is considered embryoinic bradycardia less than 7 weeks?
<85 beats per minute
what is considered embryonic bradycardia over 7 weeks gestation?
<100 beats per minute
when should the embryo be seen with TAS?
MSD 25mm
when should the embryo be seen with TVS?
MSD 16mm
when should the yolk sac be seen with TVS?
MSD 8mm
when should the yolk sac be seen with TAS?
MSD 20mm
what is the leading cause of maternal death in the first trimester?
ectopic pregnancy
what are risk factors for an ectopic pregnancy?
- PID
- tubal surgery
- maternal congenital anomalies
- late primiparity
- defective zygote
- fertility treatments
- intrauterine device (IUD)
where is the most common location of an ectopic pregnancy?
ampulla region of fallopian tube (75%-80%)
what are locations for an ectopic pregnancy?
- cervix
- ovary
- uterine cornua
- broad ligament
- abdomen
what is a heterotopic pregnancy?
intrauterine pregnancy and ectopic pregnancy
what are the signs and symptoms of an ectopic pregnancy?
- intrauterine pseudodac or decidual reaction
- postive pregnancy test
- poor correlation with B-hCG
- bleeding and severe pain
- cul-de-sac fluid
- adnexal ring sign
- complex adnexal mass with or without live pregnancy
- significant amount of hemoperitoneum
what can a trophoblastic be?
- benign
- malignant
- malignant/metastatic
what are the types of trophoblastic diseases?
- complete hydatiform mole
- hydadiform mole with coexistent fetus
- partial mole
- invasive mole
- choriocarcinoma
what are the risk factors for trophoblastic disease?
- maternal age
- previous history of a molar pregnancy
what is a major sign of gestational trophoblastic disease?
hyperemesis
what are symptoms of molar pregnancy?
- vaginal bleeding
- hyperrmesis
- preeclampsia
- thyrotoxicosis
- respiratory distress
what is elevated with molar pregnancy?
elevated B-hCG
what is low in molar pregnancy?
AFP levels are low in a hydatiform mole
what does organs look like with a molar pregnancy?
uterus is greater in size than the expected gestatinal age + bilateral ovarian enlargment owing to theca-lutein cysts
what is considered a complete hydatioform mole?
paternal origin and devoid of maternal chromosomes which results in a 46 XX karyotype without fetal development
what is considered a partial hydadiform mole?
triploidy with a 69 XXX of which 23 chromosomes are of the maternal contribution and 46 chromosomes are of the paternal contribution
what gives a snowstorm appearance?
hydropic chorionic villi
what is an invasive hydatiform mole?
when the hydropic villi of a partial or complete mole invade the uterine myometrium and sometimes uterine wall
what is a choriocarcinoma?
a malignant tumour that arises from the trophoblastic epithelium
where may a choriocarcinoma metastasize?
lung skin intestines liver spleen heart brain
what presents clinically with a choriocarcinoma?
- vaginal bleeding
- enlarged uterus and ovaries
- elevated B-hCG
when may a choriocarcinoma occur?
develop after a molar pregnancy but can also occur after a normal pregnancy, SAB, or ectopic pregnancy
why is there an increase of incidence of multiple gestations?
throughout the years there has been a widespread of reproductive technology and an aging maternal population
what is another name for chorionicity?
placentation
what is dichorionic?
two chorions produce 2 placentation sites
is dichorionic or monochorionc more common?
dichorionic
what presents the least risk for twins?
dichorionic
what is monochorionic?
the development of one chorion results in a shared placental site, which places the pregnancy at higher risk
is monoamniotic or diamniotic at higher risk?
monochorionic because of risk of cord accidents
what is zygosity?
refers to the number of zygotes produced at the time of fertilization
when does dizygotic twins occur?
when 2 seperate ova are fertilized by 2 seperate sperm cells
when does monozygotic twims occur?
when one ovum is fertilized by a single sperm
the later the cleavage occurs the ___________
more that is shared
when does conjoined twins occur?
13 days after conception
what are clinical signs of multiple gestation?
- large for dates
- hyperemesis
- hypertension
- increased human chorionic gonadotropin
- increased alpha feta protein
what is the most common complication with multiple gestations?
premature labour
because of increasd uterine volume
twin pregnancies are ____ more likely than singleton pregnancies to be complicated by premature labour
5X
triplet gestations are ______ higher than singelton pregnancies to be complicated by premature labour
10X
what is considered a significant finding associated with premature delivery?
cervical length of less than 2.5 cm or the presence of funneling
a fetal weight less than what is suggestive of IUGR?
10th percentile
what are other signs of IUGR?
- oligohydramnios
- high resistance umbilical artery pulsed doppler waveform
what may IUGR be the result of?
result of twin-twin transfusion
The incidence of a major fetal anomaly in a multiple gestation is _____ compared with ______ in a singleton pregnancy
4%
2%
what malformation is the most common in multiple gestations, especially monozygotic twins?
central nervous system
twins and especially triplets are at an increased risk of what?
cerbral palsy
what are common maternal complications?
pregnancy-induced hypertension and pree-clampsia are
what are the features of eclampsia?
- hypertension
- edema
- proteinuria
- convulsions
what is hypertension associated with?
IUGR and placental abruption
what do we assess with placental sites?
- the number and location of the placentas
- membrane thickness
- the appearance of the membrane attachment
what should be done when the 2 cord insertion sites can be seen in the same plane?
one should look for the presence of an interfetal membrane
if no membrane exists between the cord insertion sites what are the twins most likely?
monochorionic, monoamniotic
what does the intertwin membrane seperating monochorionic twins consist of?
2 layers of amnion
what does the monochorionic intertwin membrane measure?
1mm
what does the membrane seperating the monochorionic, diamniotic form?
a T shape
what does the membrane seperating the dichorionic, diamniotic twins look like?
twin peak or a lambda sign
what is often the first sign of complcations of multigestational pregnancies?
a difference in growth (discordant growth)
when is the growth of twins considered discordant?
if the difference in their birth weights is greater than 20% of the larger twins weight
what is the main factor contributing to increased mortality rates of monoamniotic twins?
cord entanglement
what do we look at in cord entaglement?
evaluate for increased arterial and venous velocities and for evidence of high resistance in the umbilical artery
what is the most common method of evaluating AVF in a multiple gestation?
the single pocket method and subjective evaluation
what is considered polyhydramnois?
MVP that exceeds 8cm or
AFI exceeding 18-20
what may be a feature of a recipient twin in a gestation with twin-twin transfusion?
excess fluid
what suggests oligohydramnois?
MVP less than 2cm or
AFI less than 5cm
what can olighydramnois, a complication associated with donor twin in gestations with twin-twin transfusion, be caused by?
IUGR
what does oligohydramnois cause wth the amniotic membrane?
stuck to the uterine wall
50% of patients with 3 or more gestational sacs are at risk for spontaneoud reduction before when?
12 weeks of gestation
the risk of co-twin death for monochorionic twins was _________ than for dichorionic twins
5 times higher
what is vanishing twin?
twin gestations diagnosed in the 1st trimester, one twin dies, leaving behind an empty sac and it may be completely reabsorbed
what is fetal papyraceus?
refers to a twin fetus that has died early in development and has been pressed flat against the uterine wall by the living fetus
what does pagus mean?
joined (conjoined twins)
what are conjoined twins?
monozygotic twins that are physically united at birth as a result of incomplete division of the embryonic disk
what is craniopagus?
twins who are joined at the head
what is thoracopagus?
twins are joined at the thorax
what is omphalopagus?
twins are joined at the anterior mid trunk
when is conjoined twins suspected?
when monoamniotic twins do not move away from each other and is confirmed when fusion of the fetal parts is identified
what is twin-twin transfusion caused by?
unbalances shunting of blood from one twin to the other
where are vascular connections found?
in virtually all monochorionic twins
what is the bloodflow in twin-twin transfusion?
the donor twin pumps blood from its arterial system into the venous system of the recipient twin
what is the blood flow in twin-twin transfusion for the donor twin?
donor twin recieves less bloos and is usually growth restricted, hypovolemic, and anemic
what is the blood flow in twin-twin transfusion for the recipient twin?
recipient twin recieves too much blood, and although it may be normal in size, it is often macrosomic and hypervolemic
what can the extra blood flow and work placed on the recipient twins heart result in?
fetal hydrops or heart failure
what does TRAP syndrome stand for?
Twin Reversed Arterial Perfusion Sequence
what is TRAP syndrome?
rare condition that complicates approximately 1% of monochorionic pregnancies
how does TRAP occur?
occurs because of paired artery-artery or vein-vein anastomosis within the shared placenta
which twin in TRAP has normal circulation?
the pump twin or normal twin
what does the recipient twin in TRAP lack?
a functional heart, allowing perfusion of the normal twin to pump blood into the acardiac twin
what is the blood flow to the acardiac twin like?
umbilical arteries and into the internal iliac arteries is retrograde
what results in abnormal devlopment especially in the upper body in TRAP syndomre?
limited amounts of oxygen and nutrients are delivered to torso and lower extremities
what is common in TRAP syndrome?
clubbing of the feet or absent toes
