normal 1st trimester development

conception is the first day of pregnancy

conceptual age

• first day of the last menstrual period begins gestation (add two weeks to conceptual age)

• used by clinicians and sonographers

gestational age/ menstrual age

conceptus for the first 12 days after conception

zygote

conceptus from implantation until the end of the 10th week

embryo

embryo after the first 10 weeks

fetus

ovulation typically occurs on day?

day 14 of the 28 day cycle

what occurs during ovulation?

• mature ovum is released

  • swept up by the fimbria

ruptured follicle forms the corpus luteum and begins secreting?

• progesterone and small amounts of estrogen

if fertilization occurs: corpus lute will remain sustained by?

HCG

if fertilization occurs; the endometrium continues to?

grow thickened and echogenic

a fertilized ovum

zygote

zygotę contains 16-32 cells

morula

morula continues to expand up to 200-300 cells

blastocyst

enters the uterus 4-5 days post fertilization

blastocyst

cells form the wall of the blastocyst

trophoblastic cells

forms the chorion and placenta

trophoblastic cells

cells that secrete hCG

trophoblastic cells

cluster of cells inside the blastocyst

inner cell mass (embryo blast)

becomes embryo, yolk sac, and amnion

inner cell mass

trophoblastic cells…decidualized endometrial tissue

eat into

when can hug be detected on a pregnancy test?

when the zygote has buried itself within one wall of the uterus

• changes to the endometrium that occur in response to progesterone

• prepares (and maintains) the endometrium during pregnancy

• first signs of an IUP around 5 weeks

decidualization

3 decidual layers

• basalis

• capsularis

• parietalis

endometrial tissue deep to the implantation site (myometrial side)

decidua basalis

inner villi ring covering the gestational sac

decidua capsualris

outer ring of the endometrium

decidua parietali aka decidua vera

• fluid filled structure surrounded by two echogenic rings

• reliable sign of an early pregnancy

double decidual sign

chorion is made from what cells?

trophoblastic cells

• portion of the chorion without villi

• will become the chorionic membrane/cavity

chorion laeve

round or oval shaped cystic structure within the endometrium

GS

…the first monographic sign of an IUP

GS

GS can be seen TA somtimes at…and always at…

5 weeks, 5.5 weeks

GS can be seen TV sometimes at…and always at…

4 weeks, 5 weeks

a normal GS is expected to be visible when the hCG level is greater than 1000-2000mIU/mL

small intrauterine fluid collection with rounded edges appears at?

4-5 weeks

yolk sac sign of pregnancy appears at?

5.5 weeks

double bleb (fetal pole) sign appears at?

6 weeks

amnion appears at (gummy bear) ?

7-8 weeks

• fluid -fillecd space outside of the embryonic sac between the chorion and amnion

• early gestation this city occupies the entire GS

chorionic cavity

around …the amnion and chorion fuse (chorionic cavity is no longer vis)

14-16weeks

encase the developing embryo

amnion

amniotic cavity lies between then?

embryo and amnion

tiny amnion and secondary YS seen (double bleb sign) when?

week 4.5-5.5

amnion is no longer seen at?

fused with chorion. no longer seen by 14-16 weeks

secondary YS forms around days? and visualized with US around?

27-28 days. 5-5.5 weeks

supplies nutrients to the embryo until the placenta is developed

YS

connector tube is called the yolk stalk or?

vitelline duct

diameter…mm is normal for YS

<5mm

diameter of …mm of YS is usually indicative of an binormal pregnancy

>6mm

diameter of YS is measured how?

inner to inner

embryo should be seen at

week 5.5-6

embryo should be seen MSD is…

>10mm

HR should be seen with the CRL of?

4mm

embryo should be seen along the perimeter of?

YS

development and closure of the neural tube…

week 5-6

formation of 3 primary brain vesicles

week 6

rhombencephalon divides forming the cystic rhomboid fossa and is seen on US as cystic structure in the cranium at what week?

week 8-10

heart has two cardiac tubes at week?

5

• heart begins to beat

• umbilical vessels are functional

at what week?

weeks 5-6

cardiac activity should be seen at …days or when CRL is…

46 days, CRL is >4mm

… embryonic heart rates of 90-110 increase to rates of 120-140 at…., with further increase rates of 130-160 at….

6w, 9w, 12w

heart has 4 chambers at weeks?

8-9

peripheral vascular system is developed at weeks?

10-11

primate gut formed at week?

6

gut herniated into base of the umbilical cord at week?

8-12

rectum and urogenital sinus separate at week?

8-9

anal membrane perforates at week?

10-11

kidneys are formed in pelvis at week?

5

• kidneys ascend from the pelvis

• kidneys begin urine production

at weeks?

8-12

rhombencephalon can be see at week?

week 8

mid gut herniation can be seen at?

week 8-12

limb movement seen at week?

9

embryo flexes/extends at week?

10