Key Terms: Test2 Flashcards
Indications for 1st trimester exams
confirm presence of an intrauterine pregnancy, evaluate a suspected ectopic pregnancy, define the cause of vaginal bleeding, evaluate pelvic pain, estimate gestational(menstrual) age, diagnose or evaluate multiple pregnancy, confirm cardiac activity, an adjunct to chorionic villous sampling, embryo transfer, assess for certain fetal anomalies, evaluate maternal pelvic or adnexal mass, screen for fetal aneuploidy, evaluate suspected hydatidiform mole
indications for 2nd and 3rd trimesters
evaluation of gestational age, fetal growth, vaginal bleeding, cervical insufficiency, abdominal and pelvic pain, determination of fetal presentation, eval of suspected multiple gestation, adjunct to amniocentesis, significant discrepancy between uterine size and clinical dates, eval of pelvic mass, exam of suspected hydatidiform mole, adjunct to cervical cerclage placement, eval suspected ectopic preg, fetal death, uterine abnormality, fetal well-being
types of OB exams
1st trimester exam
1st trimester nuchal translucency
standard obstetric exam
repeat obstetric exam
limited obstetric exam
specialty obstetric exam
patient history
information obtained before exam
nageles rule
EDD = LNMP - 3mo + 7days
LMP = EDD - 3mo + 7 days
(EDD-estimated date of delivery)
(LNMP-last normal menstrual period)
maternal risk factors
latex allergies
supine hypotension
taking any meds
pain, bleeding, decreased fetal movement
congenital anomalies-maternal age, 1st or 2nd maternal serum biochem values, maternal disease, pregnant uterine cavity too big or too small, previous child born with chromosomal disorder, exposure to known teratogenic drug or infectious agent known to cause birth defects
fetal anatomy
head, face, and neck: cerebellum, choroid plexus, cisterna magna, lateral cerebral ventricles, midline falx, cavum septi pellucidi, upper lip
chest: four chamber view of the fetal heart
abdomen: stomach(presence, size, and situs), kidneys, bladder, umbilical cord, number of vessels
spine: cervical thoracic, lumbar, and sacral spine
extremities: presence or absence of arms and/or legs
gender: medically indicated in low-risk pregnancy, only for eval of multiple gestations
morality and ethics in OB sonography
morality-the protection of cherished values that relate to how persons interact and live in peace (concerns right and wrong conduct-what we ought not to do, the good and bad character-the kinds of persons we should become and the virtues we should cultivate in doing so)
ethics-the study of what is good and bad of moral duty and obligation; systematic reflection on and analysis of morality
nonmaleficence
refraining from harming oneself or others
appliation of the principle of nonmaleficence requires the sonographer to obtain appropriate education and clinical skills to ensure competence in performing each required examination
conceptual age
(embryonic age)
age of embryo stated as time from date of conception
embryologists state time in conceptual age, with conception as the first day of pregnancy
menstrual age
(gestational age)
length of pregnancy defined in the U.S. as the number of weeks from first day of last menstrual period (LNMP)
clinicians and sonographers use gestational age to date the pregnancy
zygote stage from conception through implantation
mature ovum-released at day 14
fertilization-occurs 1-2 days after ovulation
zygote-fertilized conceptus, 12 days after conception
morula-16 cell (zygote forms 16 cell morula)
blastocyst-further cell proliferation brings the morula to this stage, enters uterus 4-5 days after ovulation
implantation-completed within 12 days post fertilization
time of iimplantation until end of 10th wk-embryo
after 10wks-fetus
maternal serum biochemistry
at 9-10wks, hCG levels plateau and decline
increased levels-screening marker for Down’s during 1st and 2nd trimesters
component of risk assessment(1st trimester), triple screen and quad test (2nd trimester)
PAPP-A-low levels may be a marker for Down’s during 1st trimester
decidua basalis
uterine decidual surface on the maternal side of the placenta
the part of the decidua that unites with the chorion to form the placenta
decidua capsularis
uterine decidua on the surface of the implantation site
the part of the decidua that surrounds the chorionic sac
double decidual sac sign
interface between the decidua capsularis and the echogenic, highly vascular endometrium
highly vascular surface on th opposite side of the endometrial cavity
features of a normal gestational sac
round or oval shape
fundal position in uterus
eccentrically placed position in middle portion of uterus
smooth contours
decidual wall thickness > 3mm
embryo should be seen with MSD> 18mm
gestational sac grows at rate of 1mm/day
yolk sac
earliest intragestational sac anatomy seen
normally seen from 5wks of gestation
functions of secondary, or sonographic, yolk sac in embryonic development-provide nutrients to developing embryo, hematopoiesis, development of embryonic endoderm, which forms primitive gut
typically reabsorbs by 12wks
embryo
beginning of 5th wk, bilaminar embryonic disk undergoes gastrulation and converts into trilaminar (three germ layer) embryonic disk
early embryo not often identified until heart motion detected at approx 5 1/2wks
embryo seen between yolk sac and immediate gestational sac
embryonic folding continues-creating yolk stalk, which later forms into umbilical cord
beginning of 6th wk, trilaminar embryonic disk folds into C-shaped embryo
rhomboencephalon
1 of 3 primary vesicles are seen within the fetal brain(prosencephalon, mesencephalon, rhomboencephalon)
rhomboencephalon- divides into two segments: cephalic portion-mesencephalon, caudal component- myelencephalon
once it divides with its corresponding flexure, the cystic rhomboid fossa forms
hCG levels in 1st trimester
direct relationship exists in early pregnancy between sonographic findings and quantitative serum hCG levels
gestational sac size and hCG levels increase proportionately until 10wks
ectopic pregnancy hCG levels are lower than normal
hCG levels fall before spontaneous expulsion of nonviable gestations
limb development
limb buds embryologically recognizable during 6th wk of gestation, as is embryonic tail, which is not unlike that of a tadpole
upper limbs form first, then lower limbs
hands and feet develop later in 1st trimester (completely formed by end of 10th wk)
sonographically, limb buds may be seen from 7th wk on
limbs not routinely detected til calcification of long bones begins at 10wks
fingers and toes have been identified using transvaginal sonography at 10wks
skeletal ossification
calcification of clavicle begins at approx 8wks
followed by ossification of mandible, palate, vertebral column, neural arches
frontal cranial bones begin to calcify at 9wks, followed by long bones
palate fusion occurs late in 1st trimester
sonographically, embryonic face cannot typically be seen with diagnostic detail
by 9th wk, maxilla and mandible noted as brightly echogenic structures
further bony palate development may be visualized from 10th wk
physiologic herniation of bowel
anterior abdominal wall developed by 6wks gestation from fusion of four ectomesodermal body folds
primitive gut formed simultaneously as dorsal yolk sac incorporated into the embryo
midgut, derived from primitive gut, develops
forms majority of small bowel, cecum, ascending colon, proximal transverse colon
midgut herniates into base of umbilical cord until approx 11th wk when it begins to descend back into abdomen
gestational sac size
mean gestational sac size correlates closely with menstrual age during early pregnancy, size remains accurate through 1st 8wks
gestational sac size (mean sac diameter) determined by average sum of length, width, and height of gestational sac
MSD = length(mm) + width(mm) + height(mm)/3
MSD(mm) + 30 = menstrual age (days)
menstrual age (days)/7 = menstrual age (weeks)
crown rump length (CRL)
determination of 1st trimester gestational dates by direct measurement of embryo using CRL 1st reported in 1975
produced gestational dating standard deviations of +/- 5-7 days, by far the most accurate dating parameters within obstetric biometry
CRL measurements can be obtained as early as 5 1/2wks using transvaginal sonography
visualization of embryonic heart motion is marker signifying beginning of CRL measurements
CRLs considered most accurate method for dating through 12wks gestation
after 12 wks, fetus begins to curl, making measurement of length more difficult
