First Trimester Flashcards
Ch. 3
when is the gestational age
from the first day of lmp
when is conceptual age
calculated from fertilization, 2 weeks less THAN GESTATIONAL AGE
what is TVS (transvaginal sono) used for
to identify a pregnancy 1 to 2 weeks earlier than TAS
what are the progression stages of pregnancy
embryonic period
fetal period
when is the embryonic period
from fertilization +8 weeks= 10 weeks GA
when is the fetal period
less than 10 weeks GA
when is hcg produced
on day 28
parts of the blastocyst
amniotic cavity
exocoelomic membrane
exocoelomic cavity
decidua
is the transformed endometrium during pregnancy
what are parts of the decidua
decidua basalis
decidua capsularis
decidua vera or parietalis
what surrounds the membrane
amnion
what is the double bleb sign
amnion and yolk sac
when does the double bleb sign fuse
it fuses with chorion by 12-16 weeks
when should chorioamniotic separation occur
by 16 weeks, can be a concern if not by then (anomaly)
*what is allantois
it is part of the connecting stalk of the embryo
what does allantois give rise to
the umbilical cord and bladder (urachus)
what connects the embryo to the yolk sac
viteline duct (omphalomesenteric)duct
what is another name for viteline duct
omphalomesenteric
what is the chorion
a trophoblast surrounds the blastocyst and becomes the placenta
how does the chorion appear
as an echogenic ring of the gestational sac
what does the chorion secrete
human chorionic gonadotropin hCG
what is the yolk sac responsible for
hematopoiesis an transfer of nutrients
what is hematopoiesis
blood formation
what does the yolk sac produce
alpha fetoprotein
when is secondary yolk sac seen
5-6 weeks
what is Meckle’s diverticulum
outpouching of the terminal ileum in adults
where does the intrauterine gestational sac lie
between decidua capsularis and decidua parietalis
what is DDSS
double decidual sac sign
pseudosac
associated with ectopic pregnancy
how much does the gestational sac grow per day
1-2mm
gestational sac without embryo
measure sac for GA- just inner wall to inner wall do not include the decidual fringe
formula for GA
MSDmm+ 30
formula for MSDmm
sac length+height + width
weeks 3-8 the developing embryo is vulnerable to
teratogens
what are the germ layers
endoderm, mesoderm, ectoderm
when do the germ layers develop
weeks 3-8
what forms the CNS
neural tube
when is organogenesis complete by
10 weeks
what does the neural tube develop into
the brain
what are the three segments of the neural tube
forebrain (prosencephalon)
midbrain (mesencephalon)
hind brain ( rhombencephalon)
spell other name for hind brain
rhombencephalon
when is rhombencephalon seen by
10 weeks
what is CRL
crown to rump length
what is CRL used for
to obtain gestational dating
what is the most accurate measurement during 1st trimester
CRL
what do you exclude from CRL
extremeties and yolk sac, just measure head to butt
when is CRL images
TAS by 6-7 weeks
CRL formula
convert mm to cm
add 6.5
=GA in weeks
FHR is documented in what mode
M mode
What should the beats per minute be for FHR
120-160
140 bpm average
low embryonic/ fetal HR
pregnancy failure
when can you scan TAS
and what should be seen
when the gestational sac measures 20-25 mm
fetal pole with heart motion should be seen
normal fetal primitive hindbrain aka
rhombencephalon
what is mistaken for fluid collection in fetal head
and when is it seen
hydrocephalus
usually seen at 10 weeks GA
when is amnion seen
at 5-6 weeks
what is NT used for
to screen for genetic anomalies
what is physiological midgut herniation
intestinal enlargement
herniates to base of umbilical cord
when does mid gut herniation occur
between 8-12 weeks/ rapid growth of embryo
resolves by 12th week
what is physiological midgut herniation accused of
omphalocele
gastroschisis
when is a corpus luteum cyst seen
may be seen during early pregnancy
what hormone produced from the corpus luteum maintains the pregnancy
progesterone
trophoblastic cells of placenta take over until?
usually resolves by 12 weeks
if cyst persists after 16 weeks what might it be
a simple cyst
what is produced by the trophoblast
hCG
what does the hCG stimulate
it stimulates the corpus luteum to produce progesterone and estrogen
what sustains the pregnancy
the corpus luteum
how are hCG samples obtained
blood and urine
hCG doubles every____hrs
48 hours
what is a blastocyst
product of conception
