Obstetric Ultrasound (PBR 1)

Question 1

The first trimester covers what period?

Answer 1

From conception to the end of the 13th menstrual week.

This include the entire embryonic period (0 to 10 weeks) and is a tume of dyanamic growth and the differentatiation and development of most organ systems.

Question 2

The early gestational sac can be seen by transvaginal sonography at how many weeks?

Answer 2

3.5 to 4.5 menstrual weeks

As a tiny cystic structure implanted within the echogenic decidua, the intradecidual sign.

Question 3

A normal gestational sac is visualized by the transabdominal apprach by how many weeks?

Answer 3

5 menstrual weeks

Question 4

The normal gestation sac appears on ultrasound as what?

Answer 4

As a smoothly contoured, round, or oval, fluid-containing structure positioned within the endometrium near the funds of the uterus.

Question 5

The normal gestation sac has an echogenic border greater than how many mm thick?

Answer 5

2 mm thick

Which represents the choriodecidual reaction

Question 6

This sign is produced by visualization of three layers of decidua early in pregnancy (After 5 weeks).

Answer 6

Double decidual sac sign

It is evidence in about 85% of normal pregnancy.

Question 7

This term refers to the endometrium of the pregnant uterus.

Answer 7

Decidua

Question 8

The decidua vera lines the ______.

Answer 8

Endometrial cavity

Question 9

The decidua capsularis covers the ______.

Answer 9

Gestational sac

Question 10

The decidua basalis contributes to the formation of the _____ at the site of implatation.

Answer 10

Placenta

Question 11

This is a 2- to 6 mm diameter, spherical, cystic structure that is connected to the midgut of the embryo by a think, stalk, the vitelline duct.

Answer 11

Yolk sac

It is generally the earliest structure visualized within the gestation sac and serves as a definitive evidence of early pregnancy.

Question 12

The yolk sac should always be visualized in the normal pregnancy in gestational sacs of how many mm in diameter?

Answer 12

20-mm mean sac diamater (MSD) by transabdominal ultrasound
8 mm MSD by transvaginal ultrasound

Embryo:
MSD greater or equal to 25 mm on transabdominal US
MSD greater or eqaul to 16 mm on TVS

Question 13

The yolk sac is general seen between how many weeks of gestational age?

Answer 13

5 to 12 weeks of gestational age

Question 14

The earliest demonstration of the embryo is the ______ sign, produced by the amniotic sac and the yolk sac with the embryonic disc between them.

Answer 14

Double bleb sign

Question 15

Embryos as small as how many mm can be detected by transvaginal ultrasound?

Answer 15

2 mm

Question 16

This develops on the ovary at the site of the dominant follicle from which ovulated occurred.

Answer 16

Corpus luteum

The corpus luteum secretes estrogens, progesterone, and other hormones that are essential for establishing and maintaining pregnancy.

Question 17

This is measured from the top of the head to the bottom of the torso of the visualized embryo or fetus.

This is useful until about 12 weeks GA, when other fetal measurements become more accurate.

Answer 17

Crown-rump length

Question 18

This is measures on an axial image of the fetal head at the level of the third ventricle and thalamus.

By convention, the measurement is made from the outer table near the cranium to the inner table of the far cranium.

Answer 18

Biparietal diameter

This measurement is affected by head shape and provides an inaccurate estimate of GA if significant dolicehocephaly (elongated skull) or brachycephaly (round skull) us present.

Question 19

This is the outer perimeter of the fetal cranium measures in the same plane as the BPD.

Answer 19

Head circumference

The HC measurement is relatively independednt of head shape.

Question 20

This is the outer perimeter of the fetal abdomen measures on an axial plane image at the level of the intrahepatic portion of the umbilical vein.

Answer 20

Abdominal circumference

Question 21

This is the measurement of the ossified portion of the femoral diaphysis.

Answer 21

Femur length

The entire femur must be imaged, and the femoral shaft must be centered in the beam so that it casts an acoustic shadow.

Question 22

Normal placenta is first apparent on ultrasound at about how many weeks?

Answer 22

About 8 weeks as a focal thickening at the periphery of the gestational sac.

Question 23

The disc-like shape of the placenta becomes evident by how many weeks?

Answer 23

12 weeks

By 18 weeks the placenta is finely granular and homogeneous with smooth covering chorionic membrane along its fetal surface.

Question 24

The _______ of the decidual and myometrial veins forms a prominent sonographic landmark.

Answer 24

Retroplacental complex

Question 25

The normal placenta has a maximum thickness of how many cm?

Answer 25

4 cm

A minimum thickness of 1 cm

Question 26

The normal umbilical cord consists of how many artery(ies) and vein(s)?

Answer 26

Two arteries and one vein

Surrounded by Wharton Jelly

Question 27

As pregnancy advances, ______ becomes the major source of amniotic fluid.

Answer 27

Fetal urine

Question 28

The composition of amniotic fluid is dynamic, with turnover of the entire volume every how many hours?

Answer 28

3 hours

Question 29

The fetus swallows amniotic fluid what what rate?

Answer 29

At a rate up to 459 mL per 24 hours

Question 30

This is a rough ultrasound measurement of amniotic fluid volume obtained by measuring the vertical diameter of the deepest pockets of fluid in the four quadrants of the uters and adding these values together.

Answer 30

Amniotic fluid index

Pockets are selected that do not include fetal parts or umbilical cord.

Question 31

Normal values of the amniotic fluid index.

Answer 31

5 to 20 cm