Normal Amniotic Fluid Index Size on Ultrasound
Learn the ultrasound threshold for polyhydramnios: an amniotic fluid index (AFI) greater than 25 cm defines abnormal amniotic fluid volume in pregnancy.
Obstetrics
16 entries
A
Normal Amniotic Fluid Index Size on Ultrasound >24 Weeks
Learn the normal amniotic fluid index (AFI) threshold on ultrasound after 24 weeks and the clinical significance of AFI below 5 cm.
C
Normal Cephalic Index Size on Obstetric Ultrasound
The normal fetal cephalic index ranges from 75–85 on obstetric ultrasound, helping detect head shape abnormalities that affect biometric accuracy.
Normal Cervical Length in Pregnancy: Ultrasound Reference
Normal cervical length before 36 weeks gestation is greater than 3 cm on ultrasound; shorter measurements indicate increased risk of preterm labor.
F
Normal Fetal Heart/Thorax Area Ratio Size on Ultrasound
Normal fetal heart/thorax area ratio on ultrasound measures 0.2–0.35, a key four-chamber view parameter for detecting cardiomegaly or small heart.
Normal Fetal Heart/Thorax Circumference Ratio Ultrasound
Normal fetal heart circumference to thorax circumference ratio is less than 0.5 on ultrasound, a key marker for cardiomegaly assessment.
Normal Fetal Lateral Ventricle Diameter Size on Ultrasound
Normal fetal lateral ventricle diameter measures less than 10 mm on coronal ultrasound — a key threshold for detecting ventriculomegaly in obstetric imaging.
Normal Fetal Renal Pelvis Diameter Size on Ultrasound
Normal fetal renal pelvis diameter is <4 mm before 32 weeks and <7 mm after 32 weeks on prenatal ultrasound, guiding hydronephrosis assessment.
Normal Fetal Thorax/Abdomen Circumference Ratio on Ultrasound
Normal fetal thorax-to-abdomen circumference ratio is >0.77 on ultrasound, a key marker for detecting thoracic hypoplasia and lethal skeletal dysplasias.
G
Normal Gestational Sac Diameter Size on Ultrasound
Normal gestational sac diameter on ultrasound follows the Age − 30 mm rule in the first trimester, with key thresholds guiding early pregnancy assessment.
M
Normal Maximum Vertical Pocket Size on Ultrasound
Learn the normal and abnormal Maximum Vertical Pocket thresholds on obstetric ultrasound, including the >8 cm cutoff for polyhydramnios diagnosis.
Normal Maximum Vertical Pocket Size on Ultrasound >24 Weeks
Learn the normal maximum vertical pocket threshold for diagnosing oligohydramnios after 24 weeks on obstetric ultrasound, with clinical and technical guidance.
N
Normal Nuchal Thickness Size 18–22 Weeks Ultrasound
Normal fetal nuchal fold thickness measures less than 6 mm on ultrasound between 18–22 weeks; values at or above this threshold raise concern for aneuploidy.
Normal Nuchal Translucency Size on Ultrasound 11–14 Weeks
Normal nuchal translucency measures less than 3 mm on ultrasound between 11–14 weeks, with values above this threshold raising concern for chromosomal abnormalities.
P
Normal Placenta Previa Distance Size on Ultrasound
Learn the normal placenta-to-os distance threshold for placenta previa on ultrasound, with clinical significance and measurement technique pearls.
T
Normal Thorax/Abdomen Circumference Ratio on Ultrasound
Normal fetal thorax circumference to abdomen circumference ratio is >0.77 on ultrasound, a key marker for detecting thoracic dysplasia.
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