OB Midterm Review.txt

• 1) confirmation of pregnancy
• 2) presence of yolk sac
• 3) position of gestational sac (not ectopic, etc.)
• 4) presence of fetal heart rate
• 5) number of embryos
• 6) estimation of gestational age
• positive pregnancy test
• missed menstrual period
• Development, growth and well-being of the fetus.
• Must image the following:
• Sag UT w/meas.
• Trv UT w/meas.
• both ovaries in Sag & Trv
• gestational sac in Sag & Trv
• yolk sac
• crown rump length-longest image possible
• posterior cul-de-sac (should be no more than 2-5 ml. of fluid)
• both adnexa in sag & trv
• look for double bleb sign (amniotic cavity & yolk sac)
• fetal heart rate (90-200 normal range)
• (TV: 5-5.5 wks., TA: 6-6.5 wks.)
• 170 by 9 wks.
• 120-160 for duration
• <8 wks.=embryo
• >8 wks.=fetus

• 3 most important findings:
• fetal growth
• fetal development
• gestational age

• Image the following:
• Amniotic fluid index(sum of 4 quads)
• cervic should be 3-4 cm long
• lower uterine segment
• placenta
• femur length
• bi-parietal diameter
• head circumference
• ambdominal circumference (most sensistive measurement for determining fetal growth)
• 4-chamber heart
• heart rate
• resistive index (umbilical cord)
• head
• spine
• chest
• abdomen
• lie
• presentation
• nuchal fold
• organ situs

• surrounds the amniotic cavity; the yolk sac is within the chorionic cavity
• the membrane that separates the amniotic and chorionic cavities is routinely visualized on endovaginal exams after 5 1/2 wks.
• should fuse at approximately 16-17 wks.

• cavity in which the fetus exists
• forms early in gestation
• fills with amniotic fluid to protect the fetus
• ***double bleb sign (amniotic cavity & yolk sac) is a sign of a viable pregnancy
• fetus should be near yolk sac

• in the amniotic cavity
• should be near the fetus

5-8 MHz

• ***Routinely the earliest intragestational sac anatomy seen
• 1) provision of nutrients to the developing embryo
• 2) hematopoiesis
• 3) development of embryonic endodorm, which forms the primitive gut
• Initially, the yolk sac is attached to the embryo via the yolk stalk, but with amniotic cavity expansion, the yolk sac, which lies between the amniotic and chorionic cavities, detaches from the yolk stalk at approximately 8 wks. of gestation.
• Typically, the yolk sac resorbs and is no longer seen sonographically by 12 wks. Persistent yolk sac does occur and may be visualized at the placental umbilical cord insertion where the amniotic and chorionic membranes are fused.

day 35 (5.14 wks.)

• visualized:
• TA: 6-6.5 wks.
• TV: 5-5.5 wks.

the interface between the decidua capsularis and the echogenic, highly vascularized endometrium

• decidua basalis--the villi on the burrowing side of the conceptus
• decidua capsularis--the villi covering the rest of the developing embryo

1 mm. per day

seen as a 1-2 mm. sac with an echogenic ring having a sonolucent center by the 5th week of pregnancy

corpus luteum

• the most common cystic structure seen in adnexa during 1st. trimester
• seen in ovary
• unilateral
• should be anechoic (if internal debris present, then it's referred to as a hemorrhagic cyst)

• the anterior abdominal wall and primitive gut are developed by 6 wks.
• because the midgut is in direct communication with the yolk sac, amniotic cavity expansion pulls the yolk sac away from the embryo, forming the yolk stalk
• as amniotic expansion occurs, the midgut elongates faster than the embryo is growing, causing the midgut to herniate into the base of the umbilical cord.
• continues to grow and rotate until 10 wks before it descends into the fetal abdomen at about the 11th wk.
• should be resorbed and not seen by the 12th wk.

rhombencephalon (hind brain)

• ***rosencephalon=forebrain
• mesencephalon=midbrain

? decidua capsularis ?

three

• umbilical arteries (2)
• umbilical vein (1)

crown-rump length and gestational sac measurement in early pregnancy

• hormone secreted by the trophoblastic cells (developing placental cells)
• can be measured in the blood or urine of mother
• ***a normal gestational sac can be consistently demonstrated when the hCG level is 1800 mIU/ml (Second International Standard) or greater when using transabdominal sonography
• but sometimes can be seen by the time 500 units are present
• MUST see a GS by the time 1200 units are present
• doubles in the blood every 48 hours
• should be less than 5000 units if fetus is deceased
• main function is to convince corpus luteum to continue secreting progesterone and to prevent corpus luteum from becoming corpus albicans

fetal swallowing and urinating

• ***Amniotic fluid is produced by:
• 1st--amnion
• 2nd--placenta
• 3rd--kidneys **90%
• 4th--skin
• 5th--lungs

16-17 wks.

choroid plexus within the lateral ventricles

fetal urinary bladder

6.5 mm

**upper limit-10mm (ventriculomegaly)

• Must visualize the falx cerebri and one of the following:
• 1) Thalamus
• 2) Cavum septum pellucidi

***should, if possible, also visualize the choroid plexus in the atrium of each lateral ventricle

• Embryo:
• 90-115 at 6wks.
• 140-160 at 9 wks.

• Fetus:
• approximately 140 throughout the remainder of the late 1st and 2nd trimesters
• normal to be 120-160 for duration of pregnancy

anembryonic pregnancy-when the mean sac diameter is 25 mm or higher, and no yolk sac or embryo is seen

• ***if yolk sac is present, but no embryo, then it's early pregnancy failure
• if yolk sac and embryo are both present, but there is no detectable heart tone, then it's embryonic demise

?? never been pregnant?

***this is a word that appears in Italian, Spanish and French(spelled nulligeste) texts, that as far as I can tell, translates to "never conceived a child," which should mean that it's the same thing as nulligravida, but it's nowhere in our book or listed as a definition on the interwebs. =(

• Any pregnancy outside thr uterus/ endometrial cavity
• 98% of ectopic fetus lie in the fallopian tubes
• Can be in cervix, abdomen or ovaries also
• Only 20% go to term
• live embryo within the adnexa is the most specific finding for ectopic gestation
• an extrauterine sac within the adnexa is the most frequent finding of ectopic pregnancy, with an thickened echogenic ring, separate from the ovary
• there is a possibility that an embryo or yolk sac may be seen
• gestational sac with a Doppler resistive index of less than 0.40
• ***The most important finding when scanning for ectopic pregnancy is to determine if there is a normal intrauterine gestation (reducing the probability of an ectopic pregnancy) or if the uterus is empty and an adnexal mass is present.
• As many as 20% of patients with ectopic pregnancy demonstrate an intrauterine saclike structure knkown as the pseudogestational sac.
• 1) pseudogestational sacs do not contain either a living embryo or yolk sac
• 2) pseudogestational sacs are centrally located within the endometrial cavity, unlike the burrowed gestational sac, which is eccentrically placed
• 3) homogeneous level echoes are commonly observed is pseudogestational sacs, unlike normal, anechoic, gestational sacs
• ***these findings are best seen with endovaginal ultrasound
• peritrophoblastic flow can be seen (low-resistance (high-diastolic) pattern with fairly high peak velocities (approx. 20 cm/sec.))
• the decidual cast of the endometrium typically demonstrates a high-resistance pattern (low-diastolic component) with low peak velocities
• In early ectopic pregnancy, a hematoma may be the only sonigraphic sign, but should be distinguished from an ovatian cyst, such as the corpus luteum
• 80% will have at least 25 ml of blood in the peritoneum caused by blood escaping from the distal tube (fimbria)
• 60% will have intraperitoneal fluid on EV scan
• Look for echogenic free fluid in the pelvis, echogenic bowel segments

• ? Transverse ?
• ? Oblique ?
• ? Oblique cephalic ?

• Conceptual age (embryonic age)--used by clinicians, with conception as the first day of pregnancy
• Gestational age--used by sonographers, with the first day of the last menstrual period as the first day of gestation. Thus, the gestational age would add 2 weeks onto the conceptual age.

• ***Nagele's rule:
• LMP
• + 7 days
• - 3 months
• + 1 year
• OR
• LMP
• + 7 days
• + 9 months

• Once the rhombencephalon divides with its corresponding flexure, the cystic rhomboid fossa forms.
• The cystic rhomboid fossa can sonographically be imaged routinely fro the 8th to 11th week of gestation.
• The choroid plexus is echogenic at 9 weeks

• part of the biophysical profile
• a sonographer must observe at least one episode of extension and immediate return to flexion of an extremity or the spine
• one active extension and flexion of an open and closed hand would be a good example of positive fetal tone
• abnormal fetal tone is noted by a partial extension or flexion of an extremity without a quick return

thalamus

• 1) thoracic--4 chamber heart
• 2) lumbar--kidney & bladder
• 3) sacral--bladder

in the back of the cerebral peduncles within the posterior fossa

cerebrospinal fluid

the narrow central part of the cerebellum between the two hemispheres

• amniotic fluid index
• fetal respiration
• fetal movement
• fetal tone
• ***not always indicated, but the non-stress test is also performed as part of the biophysical profile

Wait 30-60 minutes and recheck

• lies inferior to the heart and lungs and superior to the liver, stomach and spleen
• separates the thorax and abdomen
• sonolucent or hypoechoic

abdominal circumference

• the villi on the maternal side of the placenta or embryo
• unites with the chorion to form the placenta

• usually seen when mean sac diameter is 18mm
• MUST be seen by 25mm

corpus luteum cyst

6th-7th week

? decidua capsularis ?

• trophoblastic disease where there is partial or complete conversion of the chorionic villi into grapelike vesicles
• pregnancy develops into a neoplasm
• elevated hCG levels--over 80,000 units
• characteristic "snowstorm" appearance
• moderately echogenic soft tissue mass filling the uterine cavity and studded with small cystic spaces(grape-like) representating hydropic chorionic villi, may only be specific for a second-trimester mole

• is approximately 0.1 mm/ml of growth of the mean sac diameter when the MSD is less than 15 mm
• 0.03 mm/ml of growth of the MSD through the first trimester
• ***the normal diameter of the yolk sac should never exceed 5.6 mm
• TA studies show that the yolk sac should be seen within mean sac diameters of 10-15 mm and should always be visualized with a mean sac diameter of 20 mm

• 1 mm
• ***10 mm usuallly indicated Dandy-Walker syndrome