2nd/3rd Trimester OB US (last edited 11/07/2019)
(last reviewed 11/07/2019)
(last reviewed 11/07/2019)
- Sagittal midline cervix, show internal os and placenta relationship
- Sagittal view to demonstrate fetal lie.
- At least three images of placenta (sagittal of lower edge, sagittal of upper edge, transverse)
- AFI or MVP for amniotic fluid volume. If MVP, sagittal and transverse views of largest pocket
- Depth measurement of largest amniotic fluid pocket
- Two BPD measurements and two HC measurements at level of thalami and cavum septum
- Image the cavum septum, cerebellum/posterior fossa, choroid/lateral ventricles
- Coronal view of nose, lips, mouth
- Sagittal profile of nose, lips, chin
- Axial view of neck at correct angle, color doppler if abnormal
- Three sagittal views of spine: cervical, thoracic, lumbosacral
- Three representative transverse images of cervical, thoracic, lumbosacral spine. Important to perform meticulous dynamic scan of spine transverse from cervical through sacrum to identify posterior defects
- Image diaphragm
- Image 4 chamber heart
- M-mode heart rate
- Coronal or sagittal chest/abdomen to show heart and stomach on left side
- Transverse images of both kidneys
- Sagittal images of both kidneys
- Image urinary bladder
- Image stomach
- Two AC measurements, at level of umbilical vein
- Two FL measurements
- Transverse image 3 vessel cord. RES this image.
- Transverse color doppler through fetal bladder showing 2 umbilical arteries
- Doppler of 3 vessel cord, measure SD ratio
- Cord insertion to ventral wall
- Four major extremities
- Label: stomach, kidneys, bladder, heart, posterior fossa, cervical spine, thoracic spine, lumbosacral spine, 3 vessel cord, cord insertion
- Report page (1st and 2nd pages)
- Print growth chart
Sagittal and transverse views. Show relationship to internal os.
Amniotic Fluid Volume:
Use four quadrant AFI per protocol. May also use MVP.
Show fetal lie. Fetal measurements. Fetal survey. Doppler 3-vessel cord. M-mode heart rate.
Always scan spine transverse cervical --> sacral to exclude any dysraphism
NOTES SECOND/THIRD TRIMESTER:
Our goal with respect to transvaginal scanning in second/third trimester gestations is to never miss placenta previa. We should also not miss imaging findings of cervical incompetence. As such, guidelines are as follows for second/third trimester OB US:
- Perform transvaginal US if there are findings suggesting placenta previa.
- Perform transvaginal US if the relationship of the inferior tip of the placenta and the internal cervical os has not been established on 2nd/3rd trimester prior US.
- Perform transvaginal US if the inferior tip of the placenta is <4cm from internal os on transabdominal US. https://my.statdx.com/document/placenta-previa/a6bc678f-d5a0-4199-a10c-7ba866e4079c?searchTerm=previa
- If the patient has symptoms (pain, bleeding) good images of the cervix are essential. If you cannot visualize the cervix adequately on transabdominal imaging, perform transvaginal US.
- If the cervix has abnormal morphology (funneling, Y-shaped, V-shaped, U-shaped) or appears shortened (<3cm length) on transabdominal US, perform transvaginal US.
- Perform transvaginal US if requested by referring healthcare provider.
If the patient declines, or if the referring healthcare provider indicates that he/she does not want transvaginal US performed, do not perform transvaginal US.