Assessment of the First Trimester Flashcards
decidua parietalis / decidua vera
results from hormonal influence on the uninvolved endometrial tissue
gestational sac
- Beta hCG of 1000 mIU/mL should demonstrate a GS transvaginally
- transabdominal: 5mm mean sac diameter 5-6 weeks
- transvaginal: 2-3mm about 4-5 weeks
sonographic findings of gestational trophoblastic neoplasm
- moderately echogenic soft tissue uterine mass
- cystic structures within mass
- vascular flow
- bilateral theca lutein cysts
- possible adjacent fetus
chorion frondosum
the portion of the chorion that develops into the fetal portion of the placenta
abdominal wall
- physiological herniation of the fetal bowel into the umbilical cord
- bowel returns into abdomen, adn herniation resolves by the eleventh gestational week
What should be seen during the 6th week?
- MSD 15-20mm
- yolk sac visualized
- c-shaped embryo approx 5mm
- heart rate present
cornual ectopic
- laterally placed gestational sac
- myometrium incompletely surrounds the GS
- highly vascular location
Nuchal Translucency
- first trimester screening for chromosomal abnormalities
- maximum thickness of the subcutaneous translucency betweem the skin and soft tissue overlying the cervical spine is measured
- calipers are placed on the hyperechoic lines, not in the nuchal fluid, from inner-to-inner borders
- exceeding 3 mm is abnormal
where does the zygote form?
in distal fallopian tube
What should be seen by the 5th week?
- MSD 10mm
- yolk sac seen transvaginally
- may see embryonic disc and may wee cardiac activity
what are the risk factors for an ectopic?
- pelvic infection
- IUD
- oviduct surgery
- infertility treatment
- endometriosis
- previous ectopic
decidua basalis
portion of the endometrium on which the implanted conceptus rests
skeletal system
- vertebral bodies and ribs are forming at 6 weeks
- arms and legs are forming at 7 weeks
- ossification of the vertebral bodies and rib cartilage at 9 weeks
- long bones form during the 10 week
heterotopic pregnancy
one IUP and one extrauterine
differential: bicornuate uterus pregnancy in both horns, IUP with complex corpus luteal cyst
morula
solid mass of cells formed by cleavage of a fertilized ovum
The embryo unfolds and the midgut has herniated during what week?
8th week
What is demonstrated during 12th week?
- midgut returned to abdominal cavity
- skeletal body
- fluid in stomach
- yolk sac no longer seen
chorionic plate
the part of the chorionic membranethat covers the placenta
crown-rump length
- measured until 12th gestational week
- most accurate method of dating a pregnancy
- sagittal measurement of the embryo or fetus from the top of the head to the bottom of the rump
- lower extremities are not included in the measurement
- length increases approximately 1 mm/day
What should be seen by the 4th week?
thickening of endometrium
MSD 2-3mm
decidua capsularia
decidua that covers the surface of the implanted conceptus
embryological age
length of time based from conception.
weeks 6-10
decidua parietalia
decidua exclusive of the area occupied by the implanted conceptus; aka decidua vera
embryo
- embryonic period extends from the sixth through the tenth gestational weeks
- transabdominal: usually detected within an MSD >25mm
- transvaginal: usually detected in an MSD >16mm
pseudocyesis
- false pregnancy
- psychological codition
- normal nongravid uterus
- normal adnexa
The 10th week has what sonographic findings?
- muscle movement has begun
- hyperechoic choroid plexuses
- rhombencephalon demonstrated
mean sac diameter
establishes gestional age before visualization of an embryonic disc
MSD(mm)=length+height+width/3
when is organogenesis generally completed?
by the 10th week
decidua basalis
develops where the blastocyst implants
maternal contribution to placenta
gestational trophoblastic neoplasm
- abnormal proliferation of the trophoblast
- hydatid swelling in a blighted ovum
- trophoblastic changes in retained placental tissue
what implants in the endometrium?
blastocyst
anembryonic (blighted ovum)
- zygote develops into a blastocyst but inner cell mass fails to develop
- differential: missed abortion or pseudogestational sac
complete abortion
miscarriage
differential: ectopic or early IUP
clinical findings of pseudocuesis
- nausea and vomiting
- abdominal distention
- amenorrhea
- negative pregnancy test
- differential: recent complete miscarriage
differential of gestational trophoblastic neoplasm
- incomplete abortion
- degenerating fibroid
- adenomyosis
cranium
- prosencephalon- forebrain
- mesencephalon- midbrain
- rhombencephalon- hindbrain
fallopian tube ectopic
- 95% are located in the fallopian tube
- typically in ampulla
- complex adnexal mass
- cul-de-sac fluid
- may display an extrauterine gestational sac with or without embryo
decidua capsularis
closes over and surrounds the blastocyst
clinical findings of gestational trophoblastic neoplasm
- bleeding
- hyperemesis
- elevated beta hCG
- large for dates
- no heart tones
- low maternal AFP
- preeclampsia
subchorionic hemorrhage
- low pressure bleed from implant of blastocyst
- becomes more anechoic with time
- differential: nonviable twin, incomplete abortion, placenta abruption
cardiovascular system
- first system to function in the embryo
- four heart chambers are formed by the eighth gestational week
- cardiac motion as early as 5.5 weeks
cardiac activity
- first system to function in embryo
- should be identified by 6 weeks, as early as 5.5 weeks
- 110-115 bpm before 6 weeks
- 120-160 bmp after 6 weeks
Amnion
- attaches to embryo at the umbilical cord insertion.
- expands with accumulation of amniotic fluid and growth of the embryo
- obliterates chorionic cavity by 16th week
corpus lutem during pregnancy
- secretes progestrone before placental circulation
- usually measures
- hypervascular periphery (ring of fire)
- differential: ectopic or endometrium
yolk sac
- provides nutrition to the embryo
- earliest structure visualized in the gestational sac
- attached to the embryo by the vitelline duct
- inner-to-inner border diameter should not exceed 6mm
- transabdominal: evident within an MSD of 20mm
- transvaginal: evident within an MSD of 8mm
during what week do limb buds appear?
7th week
CRL 1 cm
how long does it take fertilization to implant?
5 to 7 days
incomplete abortion
- retained products of conception
- thick and complex endometrium
- intact gestational sac with nonviable embryo
- collapsed GS
- differential: ectopic or endo dysplasia
human chorionic gonadotropian
- produced by the trophoblastic cells of the developing chorionic villi
- normally doubles every 30 to 48 hours during the first 6 weeks of pregnancy
- peaks at the tenth gestational week 100,00 mIU/mL
- declines after tenth week and levels out at about 18 weeks 5000mIU/mL
- gestaional sac should be identified transvaginally after the hCG levels reach 1000 mIU/mL and as early as 500 mIU/mL
