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54 Cards in this Set

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US is the method of choice for what 4 things?
1. dating the pregnancy
2. monitoring fetal growth.
3. assessing fetal well-being
4. evaluating fetal anomaly & maternal pelvic organs
During what pt of preg do you use transvaginal sonography?
1st trimester pregnancy to see fetal anatomic structures deep in pelvis.
Define 1st trimester
conception-end of 13th menstrual week.
what is the embryonic period?
0-10 wks. (inc risk of maldeveloment and chromosome abnormalities)
when can you detect serum beta HCG?
w/in 2 weeks of conception (as early as 23 menstrual days)
when can you see early gestational sac by transvaginal sonogram?
3.5-4.5 menstrual weeks. tiny structure implanted in echogenic decidua (the intradecidual sign)
when can you see nl gestational sac?
5 menstrual weeks by transabdominal approach.
___ is connected to the midgut of embryo by a thin stalk & is the earliest site of blood cell formation in embryo, floating freely in fluid b/w amnitic and chorionic membranes, earliest structure visualized in gestational sac, is definite evidence of early pregnancy
yolk sac
in gestational sac of 20 mm mean sac diameter by transabdominal or 8 mm diameter transvaginal,you should always been able to visualize what?
yolk sac
in 1st trimester, how do you estimate gestational age?
measure mean diameter of gestational sac (mean sac diameter) OR CRL of embryo or fetus.
The gestational age you get from MSD and CRL have what type of confidence interval?
95% confidence interval of plus or minus 6 days.
How fast does a nl gestational sac grow?
1.2mm/day MSD
Will the decidual rxn be present in intrauterine or ectopic pregnancies?
YES
How do you measure CRL?
from top of head to bottom of torso.
When the MSD exceeds ____ mm, you should see the embryo.
16 mm.
What is definitive evidence of fetal demise on US?
Absence of cardiac activity in fetus or embryo lg enough to be visualized by transabdominal US. Confirm by transvaginal US, which may demonstrate cardiac activity even in embryos as small as 1.5 mm CRL.
A tubal ring sign in the adnexa of a transverse transvaginal image is highly indicative of what?
ectopic pregnancy
What& of implanted zygotes are menstrually aborted?
40%
What % of surviving embryos will threaten to abort during 1st trimester?
25-35%
How is BPD measured?
axial image of fetal head @ level of third ventricle and thalamus. Measure from outer table of near cranium to inner table of far cranium.
Define spontaneous abortion.
Termination of pregnancy before 20 weeks gestational age by natural causes.
What % of all known pregnnacies end up in spontaneous abortions.
10-15%
What % of spontaneous abortions have chromosomal abnormlaities?
60%
are spontaneous abortions usually imaged?
no! unless it continues to bleed--look for retained POC
what is an anembryonic pregnancy?
gestational sac w/o embryo demonstrated by US thats compatible w/ very early intrauterine pregnancy or nonviable intrauterine pregnancy (anembryonic pregnancy) (blighted ovum)
Define intrauterine growth retardation (IUGR).
fetal weight below 10% for gestational age. aka intrauterine growth restriction;rates of 3-5% of healthy mothers & 25% or higher for some high-risk groups, such as hypertensive mothers
Can we age fetuses by abdominal circumference?
no, b/c they can have a growth disturbance
fetuses w/impaired intrauterine growth have inc risk of what?
intrauterine demise & perinatal mortality rate 4-8x greater than nl-sized fetuses.
growth impairment occurs during which trimesters?
2nd and 3rd. It tends to be asymmetric--fetal abdomen is disproportionately small relative to head and femur (90%)
What is the most common EXTRINSIC cause of intrauterine growth retardation?
maternal HTN.
What measurement is the single best masurement to assess fetal growth?
AC measurement.
What are the 3 sonographic criteria for IUGR?
-elevated ration of femoral length to abdominal circumference (AC);
-elevated ration of head circumference (HC) to AC;
-unexplained oligohydraminos.
On an umbilical doppler, what are some signs of worsening IUGR?
decreasing diastolic flow, absent diastolic flow and reversed diastolic flow during a cardiac cycle
_______ is first apparent on US at abour 8 weeks as a focal thickening at periphery of gestational sac. Its disc-shaped and evident by 12 wks and by 18 wks its finely granular and homogenous, w/ smooth covering chorionic memrbane along its fetal surface.
Placenta
What is a common finding in bleeding pregnant pt before 20 wks gestational age. Pts may be asymptomatic if hematoma remains confine or they may present w/ caginal bleeding if hematoma leaks thru cervix.
Subchorionic hemorrhage.
What is placenta previa?
when pt or all of placenta covers internal cervical os. At term 0.3% to 0.6% of live births. Suggested by US in as many as 45% of pregnancies examined in 1st and 2nd trimesters.
What is a 'sentinel bleed'?
painless uterine bleeding at 27-32 weeks, may be provoked w/ intercouse, contractions.
What is placental abruption?
Premature separation of normally positioned placenta from myometrium. Separation is assoc w/hemorrhage from maternal vessels @ base of placenta. in 1% of preg. & implicated in 20% of perinatal deaths.
What are the risk factors for placental abruption?
maternal HTN, cocaine abuse, smoking ,previous abruption
As pregnancy advanced, ______ becomes the major source of amniotic fluid.
fetal urine
Turnover of amniotic fluid occurs how often?
every 3 hours
at what rate does the fetus swallow amniotic fluid?
at 450 mL/24 hours
define polyhydraminos. How do you diagnose?
excessive amt of amniotic fluid, >2L of fluid at delivery. subjective diagnosis by visual inspection of US. See large pockets of fluid relative to size of fetus and age of pregnancy. 2nd clue is failure of fetal abdomen to be in contact w/ anterior and posterior uterine walls after 24 wks GA
What % of polyhydraminos cases are idiopathic?related to maternal disease? related to fetal anomalies?
60%, 15-20%, 20-25%; assoc anomalies are anencephaly, encephalocele, GI obstructions, abdominal wall defects, achondroplasia, hydrops (isoimmunization). Its assoc w/ preterm labor, premature rupture of membranes, & substantial maternal discomfort.
what is a major complications of severe oligohydraminos?
fetal lung immaturity
Describe the appearance of oligohyraminos.
fluid pockets are small or absent, fetal surface features such as face are difficult to visualize.
What are some causes of oligohydraminos.
premature rupture of memrbanes, IUGR, renal anomalies (lack of urine output), fetal death, eclampsia, postdate pregancies.
Measurement of the largest fluid pocket in vertical direction of less than ___ cm is indicative of severe oligohydraminos.
1 cm.
Twins occurs in 1 out of every _____ births.
90
Why is twin morbidity and mortality inc?
inc prematurity, polyhydraminos, inc incidence of congenital anomalies, discordant growth, cord accidents.
what is twin to twin transfusion syndrome?
result of intrauterine blood transfusion from one twin to another twin. happens in monochorionic, monozygotic twins. 15% of monochorionic multiple pregnancies. Donor twin is smaller, anemic at birth (pallor, poor peripheral perfusion). Recipient twin is larger and plethoric at birth (more than 20% larger, plethoric, ruddy, jaundice)
when does AFP reach max value?
30-32 weeks gestation. Check for open neural tube.
What is the most common neural tube defect?
anencephaly. no cranial vault & cerebral hemispheres above level of orbit.
what is fetal hydrops and what do you seen in US?
pathologic accumulation of fluid in body cavities and tissues; US: ascites, pleural and pericardial effusions, subcutaneous edema.