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biopsy of chorion frondosum through abd wall or by way of vagina and cervix at 10-13 weeks of gestation to obtain fetal cells for prenatal diagnosis of chromosomal abnormalities

conception at the first day of pregnancy

subtract 2 weeks from gestational age

• used by physicians and sonographers
• first day of the last menstural period as the beginning of gestation

add 2 weeks to on to conceptual age

after the first 10 weeks

fisrt 12 days after conception during implantation

implantation- blastocyst (7-9 days)

from implantation until the 10th wk menstural age (8th embryologic)

at 10 weeks it has everything it will ever have

ovum released on day 14 of cycle in distal 1/2 of fallopian tube, fertilization 1-2 days later

corus luteum secretes progest and estrogen

zygote divides to 16 cell morula then blastocyst

blastocyst contains trophoblastic cells in inner cell mass forms embryo

trophoblastic cell secrete hcg- maternal preg response

human chorionic gonadotrophin

causes endometrium to convert to dicidua(glycogen rich mucosa)

trophoblasts eat into decidua to create "blood pools" that form as maternal cappillaries erode to nourish the proliferating trophoblastic cells

made from lacunae and trophoblastic cells that develop into circulation complex that will sustain pregnancy

when complete the trophoblast formed primary villi which encircle early gest. sac

inner cell mass matures into bilaminar embryonic disk, future embryo, and primary yolk sac

23 days- pinched off by extra embryonic coelom and forms secondary yolk sac

• not seen sonographically
• looks anechoic at 5 weeks

seen sonographically through 1st trimester starting at 5.5 weeks, not seen after 12 weeks

btwn chorion and amnion

should not exceed 6mm

• 1. nutrients to developing embryo
• 2. hematopoiesis
• 3. develop endoderm (primative gut)

• should be seen with MSD 10-15mm
• must be seen with MSD 20mm

• weeks 4-10
• all major internal and external structure develop

• initial heart beat 5.5-6 weeks
• turns to C shape

• crown-rump legnth, (1975)
• use as early as 5.5 wks tv
• measures 35mm by end of 10th week
• use up to 12 weeks
• most accurate way to age baby +/- 4-5days

• begins last two weeks of 1st trimester (11-12)
• head is 1/2 of CRL

• increse proportionally until 10th menstural week
• sac approx 45mm
• sac can be seen transabd when hCG is 1800+ mIU/ml

• mean sac diameter
• remains accurate through first 8wks
• MSD=L(mm)+W(mm)+H(mm)/3
• MSD(mm)+30=Menstrual age (days)

level doubles every 3.5 days at less than 7 wks

if not, could be ectopic

• hCG plateau at 9-10 wks and decline
• trisomy21- levels fall slower

• Pregnancy-associated plasma protien-A
• insulin like growth factor produced by trophoblastic (placental) cells
• involved in bone and tissue formation
• increses in advancing gest, low in trisomy 21 (9-11wks)

• presence of sac
• mesurement of sac/embryo
• presence of cardiac activity
• fetal number
• uterus, adnexa, cul-de-sac

5th week of development measuring 1-2mm with an echogenic ring with solonlucent center (chorionic cavity)

myometrial or burrowing side of conceptus

villi covering of developing embryo

interface btw decidua capsularis and echogenic vascularized decidua on opposite wall of the endometrial cavity

sign of early IU gestation

• 1. when MSD is >12mm
• 2. when MSD is >18mm

Grows at rate of 1mm per day

• 1. 5-5.5 weeks
• 2. 5.5 weeks
• 3. 5.5-6 weeks

• 5 weeks, CRL 3 mm
• heart rate at 5.5 weeks (CRL >4mm)
• btwn secondary yolk sac and immediate gest sac wall
• as amniotic sac grows embryo and yolk sac become further apart

chor. surrounds the amniotic sac, yolk sac is btw the chorion and amnion

both seen after 5.5 weeks

chor. increased gain shows low level echos (increased density vs. amniotic)

chor. initial dumping ground for waste until placenta takes over

amniotic cav. expands and chorionic decreases

fusion of both (chorioamniotic fusion) at 14-15wks

smooth membrane enclosing fetus and amniotic fluid, loosly fused with outter chorionic membrane except at placental insertion of umbilical cord, where amnion is continuous with membrane surrounding umbilical cord

produced by umbilical cord, and membranes the fetal lung, skin, and kidneys

6th week from trilaminar embryonic disk

umbilical duct connecting yolk sac with embryo

incorperated into embryo developing foregut, midgut, hindgut, and GI tract, biliary, liver, pancreas

connecting lifeline btwn fetus and placenta, 2 umbilical arteries and one vein, encased in whartons jelly

6wks- spine from ectoderm- evolved from primitive neural tube-closes and can be visualized- fetal pole

• 7wks- cranial neurofoldsand closure of neuropore complete
• 7wks- brain- single fluid filled vesicle

• 8th wk- brain- three vessicles
• 1. prosencephalon
• 2. mesencephalon
• 3. rhombencephalon
• a. cephalic- mentencephalon
• b. caudal- myeloencephelon

9wks- echogenic choroid plexus

10wks- cerebellum, medulla, med. oblongota

• 6th week- limb buds recongizable (tadpole)
• upperlimbs 1st lower 2nd
• hands and feet- fingers/toes by 10th wk
• calcification of bones at 10wk- easier to see

• 8wks- calcification of clavicle
• 9wks- frontal cranial bones, mandible
• 10th- bony palate

• 6 wks- abd wall
• midgut- small bowel, cecum, asc colon, trn colon
• midgut herniates into base of umb cord
• 11wks descends into fetal abd

• first functional organ
• starts beating at 35 days (5-5.5 wks)
• 8th wk- adult heart configuration
• always seen at 46 mens days, CRL >4mm
• 6wk- 90-115 bpm
• 9wk- 140-160 bpm

two parameters used: CRL and gestational sac size

trandabd removal of amn fluid from amn cavity using us, studies of fluid determine fetal karyotype, lung maturity, and rh condition

performed at 16 wks

nuchal translucency (NT)- small amt fluid along back

risk assessment test

differences in nt btwn twins may be sign of twin to twin transfusion syndrome

absence of nasal bone associated with trisomy 21 in late 1st trimester

• increased risk of aneuploidy
• requires doppl of small fetus= only if necessary, high risk

diagnosed btwn 5.5-6 wks

• 70% all twins
• dichorionic and diamniotic

• crucial diagnosis
• 50% mortality

twins in same gest sac/chorion, 2 amnions, 2 yolk sacs, 2 embryos

• 25 weeks- many complications
• 32 weeks- high survival- some complications

• no head
• #1 neurotube defect