OB Twins and Biometry Quiz

average gestational age length

40 weeks

trimesters

1st: 1-13.6 wks

2nd: 14-26.6 wks

3rd: 27-40 wks

term

37 wks and beyond

post term/post dates

beyond 40 wks

nagele’s rule

EDD = LNMP - 3months + 7days

crucial to survey anatomy in these weeks

20-22 wks

lower uterine segment measurement

>3cm

fetal positions (planes)

longitudinal, oblique, transverse

baby can easily change position up to ____ weeks

34

cephalic or vertex

head found presenting in LUS

breech

lower body or lower extremities found in LUS

! fetal head must be found in fundus to be a true breech

breech variations

frank breech, complete breech, incomplete breech

frank breech

thighs flexed at hips

complete breech

both hips and lower extremities are in lower pelvis

incomplete breech

hips extended

one or both feet are presenting closest to cervix

single or double footling

transverse lie

suspected when a cross-section of fetal head or body is noted in long

need to document which side the head/body are on

biometry begins at ___ weeks

13

biometry standard parameters

BPD, HC, AC, and FL

biparietal diameter (BPD)

Fetal transverse cranial diameter at the level of the thalamus and cavum septum pellucidum

BPD caliper placement

outer to inner

HC caliper placement

outer to outer

head circumference (HC) equation

HC = BPD + OFD * 1.57

OFD: occipital frontal distance

use this when head is too circular or ovoid

HC equation

no _________ in HC and BPD

cerebellum

do not include _______ __________ in HC

scalp thickness

Abdominal circumference (AC)

Measurement at the level of the stomach, left portal vein, and left umbilical sign

most useful predictor of any growth abnormalities

AC

do not include ________ in AC

skin

femur length (FL)

Measurement of the femoral diaphysis

make sure beam is ________ to femur for most accurate measurement

perpendicular

femur must be __________

horizontal

what transducer do you use for FL

linear

estimated fetal weight (EFW)

measurement used to estimate the weight of the developing fetus during pregnancy

sonographic diagnosis of multiple gestations within the __ trimester has valuable information

1st

Multiple gestations are _____ risk

high

multiple gestations

significant increase in _________ and _________ rates

morbidity; mortality

multiple gestations

___-___ times greater risk than singleton

7-10

____-____ twins is the most dangerous type

mono-mono

twin peak sign

aka lambda sign

triangular appearance in chorion

di-di twins

first trimester _______ _________ measurements in multiple pregnancies may contribute to risk assessment

nuchal translucency

differences in nuchal translucency measurements between normal twins may be an early sign of…

twin-twin transfusion syndrome

growth-adjusted sonar age

Method whereby the fetus is categorized into small, average, or large growth percentile

embryonic heart rate

Heart rate before the 9th week of gestation

age range analysis

Size and proportionality of the fetal parameter expressed as age

binocular distance

Measurement that includes both fetal orbits at the same time to predict gestational age

average age

Average age of multiple fetal parameter’s age

dolichocephaly

Fetal head is relatively narrow in the transverse plane and is elongated in the anteroposterior plane

hypertelorism

Condition in which the orbits are spaced far apart

spina bifida

Failure of the vertebrae to close

platycephaly

Flattening of the vertex of the skull

anophthalmus

Absence of one or both eyes

lemon sign

Occurs with spina bifida; frontal lobes collapse inward

oxycephaly

Condition of having a relatively high cranial vault with a high or peaked appearance

microphthalmos

abnormally small eyes

banana sign

Refers to the shape of the cerebellum when a spinal defect is present

brachycephaly

Fetal head is relatively wide in the transverse diameter and shortened in the anteroposterior plane

IUGR

Condition in which fetus is not growing as fast as normal; usually considered malnourished or abnormal

Sonographically, the earliest sign of intrauterine pregnancy is the __________________, which appears as an echogenic, thickening filling of the fundal region of the endometrial cavity occurring at approximately 3 to 4 weeks’ gestation.

decidua

The sac grows rapidly in the first __________________ weeks, with an average increase of 1 mm per day.

10

When the gestational sac exceeds __________________ mm in mean internal diameter, a yolk sac should be seen.

8

Normal yolk sac size should be less than __________________ mm; greater than __________________ mm has been associated with poor pregnancy outcome.

6; 8

When the mean gestational sac diameter exceeds __________________ mm, an embryo with definite cardiac activity should be well visualized with transvaginal scanning.

16

The embryonic echoes can be identified as early as 38 to 39 days’ menstrual age, and the crown-rump length is usually ________ to ________ mm at this stage.

1-2

In general, the CRL should increase at a rate of __________________ mm per day.

8

Absence of an embryo by 7 to 8 weeks’ gestation is consistent with an embryonic demise or an __________________ pregnancy.

anembryonic

The fetal head should be imaged in a transverse __________________ section, ideally with the fetus in a direct occiput transverse position.

axial

The head shape should be __________, not round, because this can lead to overestimation of gestational age, just as a flattened or compressed head can lead to underestimation of gestational age.

oval

The calipers should be placed from the __________________ edge of the parietal bone to the __________________ edge of the opposite parietal bone, or “outer edge to inner edge.”

leading; leading

The __________________ head circumference is less affected than BPD by head compression; therefore, the head circumference (HC) is a valuable tool in assessing gestational age.

transverse

The proper coronal view should be __________________ to the standard transverse HC view passing through the thalamus.

perpendicular

One can __________________ gestational age from a dolichocephalic head or __________________ with brachycephaly.

underestimate; overestimate

The abdomen should be more __________________ than oval because an oval shape indicates an oblique cut resulting in a false estimation of size.

circular

The __________________ length is an especially useful parameter that can be used to date a pregnancy when a fetal head cannot be measured because of position, or when there is a fetal head anomaly.

femur

Humerus length is sometimes more difficult to measure than femur length because the humerus usually is found very close to the fetal __________________ but can exhibit a wide range of motion.

abdomen

The ulna can be distinguished from the radius because it penetrates much more deeply into the _______________.

elbow