Chapter 15 Flashcards
(46 cards)
When is organogenesis completed?
By 10 weeks
What are weeks 6-10?
Embryonic period
What is midgut herniation?
Intestines herniate into base of umbilical cord around week 8 and return to abdominal cavity around week 12
What is the importance of midgut herniation?
Allows room for intestines to grow and rotate
At how many weeks does the fetal period start and when does it end?
Weeks 11 to term
When does the amnion and chorion fuse?
2nd trimester
What is the purpose of the fetal period?
Time for fetal growth and maturation
What is the purpose of the crown rump measurement?
Measurement gives an accurate assessment of how far along the pregnancy is
What is MSD?
Mean sac diameter
When are the most accurate reliable dates obtained?
1st trimester
When is CRL most accurately measured?
Weeks 6-12
When is MSD used? and why?
Between weeks 5-11, to determine gestational age
What measurement provides the most accurate measurements for gestational dating?
Early CRL
What is nuchal translucency?
Accumulation of subcutaneous fluid in the nuchal region
Where is nuchal translucency typically found?
In embryos with aneuploidy
When is nuchal translucency evaluation performed?
Between 11-14 weeks
What is the normal thickness for nuchal translucency?
Less than 3 mm
What is aneuploidy?
Abnormal number of chromosomes
When doing an OB ultrasound what is the preferred method for obtaining a fetal heart tone?
M-mode
When do you typically see the gestational sac?
Week 4-5
What are some sonographic landmarks of the first trimester?
Gestational sac, yolk sac, amnion, embryo and cardiac activity
What confirms dx of IUP?
Yolk sac
What group of hormones, primarily produced in the ovaries, which affect secondary sex characteristics and the menstrual cycle?
Estrogen
What structure within the cavity of the blastocyst provides nourishment to the embryo and produces its first blood cells and is the first structure to be sonographically identified within the gestational sac?
Yolk Sac
