Interactive Transcript
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This is an ultrasound of a
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normal third trimester pregnancy.
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This is an ultrasound of a normal
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second trimester pregnancy.
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You'll notice that the probe at the skin's
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surface is curved and wide, and transabdominal
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images only were obtained for this patient.
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Often, as the pregnancy progresses,
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transabdominal images alone will be
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sufficient to evaluate the pregnancy.
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So we can see the lower uterus is filled
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with hypoechoic or dark amniotic fluid.
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We also see the fetal head.
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This additional hypoechoic structure
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lateral to the uterus or anterior
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to it is the urinary bladder.
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It's filled with urine.
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And it's important to have the urinary
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bladder distended when imaging a pregnant
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patient transabdominally because the full
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bladder can act as an acoustic window and
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provide higher quality ultrasound images.
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In the second and third trimesters of pregnancy,
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instead of using a mean sac diameter or a crown
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rump length, we'll take specific measurements
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of the fetus to estimate the gestational age.
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This is an example of the biparietal
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diameter, which is a measurement
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that's taken on the fetal skull.
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This is a sagittal transabdominal
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image of the lower uterine segment.
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We can see hypoechoic amniotic
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fluid in the lower uterus, in
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addition to the urinary bladder.
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This is the cervix, and what the sonographer is
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documenting here is that the cervix is closed.
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So this is the canal; this is the internal
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os. It does not have any fluid funneled
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within it, and so this is a closed cervix,
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which is what we're expecting to see.
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The sonographer has also documented the
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location of the placenta as she has visualized it.
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So this hyperechoic structure is the placenta.
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We see this thin, dark line
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posterior to the placenta.
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This is the retroplacental clear
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space; that's a normal finding.
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And then we see uterine myometrium beyond that.
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Another measurement that we will take in the
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second trimester pregnancy is the femur length,
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which is another estimation of fetal age.
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Finally, one of the parameters that we
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can evaluate to estimate gestational
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age of the fetus is the abdominal
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circumference, which we've taken here.
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This is another M-mode tracing
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at the level of the fetal heart.
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You can see again that the sonographer
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has placed the cursor, or the region
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of interest, over the fetal heart.
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And we're seeing rhythmic, equidistant
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deflections of this M-mode tracing.
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We can measure the distance between
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those deflections to estimate the fetal
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heart rate, which for this fetus is 143
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beats per minute, a normal heart rate
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in the second trimester of pregnancy.
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