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Normal Late first trimester ultrasound survey
A Normal Late First Trimester Ultrasound Survey typically occurs between 11 to 13.6 weeks of gestation. It is an important diagnostic tool that assesses fetal development and screens for potential abnormalities. The key components of a normal survey during this stage include:
Fetal Structures Assessed in the Late First Trimester (11w to 13w 6d)
1– Structures of neutral Positions of the Fetus
2– Cranial Structures
3–Facial Structures
4–Neck Structures
5–Thoracic Structures
6–Abdominal Structures
7–Limbs and Extremities
8–Spine
9–Genitourinary System
10– Placenta
11–Umbilical Cord
12– Amniotic Fluid Assessment
13– Maternal Anatomy Assessment
1. Structures of neutral Positions of the Fetus
A neutral position in fetal ultrasound refers to a standardized orientation of specific anatomical structures to ensure accurate measurement and assessment. This position is essential for reducing variability in measurements, particularly during the late first trimester.
 | | Neutral positions |
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1-CRL
2-NT
3-Head
4-Face
5-Abdominal wall
6-Urinary Bladder
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2– Cranial Structures
The fetal head should be in a neutral or slightly flexed position, neither excessively flexed (chin too close to the chest) nor hyperextended (head tilted backward).
 | | Cranial Structures |
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1-NT
2-Nasal bone
3-Maxilla
4-Mandible
5-Thalamus
6-Brain stem
7-Fourth ventricle
8-Choroid plexus
9-Cisterna magna |
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1-Oval head shape
2-Skul bones
3-Falx cerebri
4-Choroid plexus
5-Lateral ventricles
6-Third ventricles
7-Cortex |
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2-Skul bone
3-Falx cerebri
5-Lateral ventricles
6-Third ventricles
8-Thalimi
9-Aqueduct of sylvius
10-Cerebral peduncles
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1- Thalami
2- Developing cerebellum
3- Fourth ventricle
4- Choroid plexus of fourth ventricle
5- Cisterna magna
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1- Eyes/Orbit
2- Maxillary processes
3- Nose
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3–Facial Structures
At 13 weeks of gestation, the facial structures of a fetus are more defined and continue to develop rapidly.
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1-Nasal bone
2-Orbitas/eyes
3-Maxillary processes
4-Maxilla-alveolar ridge
5-Mandible
6-Mandibular gap
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4–Neck Structures
5–Thoracic Structures
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1-Lungs
2-Ribs
3-Thorasic aorta
4-Right ventricle
5-Left ventricle
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6-Cardiac axis
7-Diastolic ventricular filling
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1-Pulmonary
2-Transverse aortic arch
3-superior vena cava
4-Trachea
5-Systolic flow in great vessels
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1-Lungs
2-Stomach in abdomen
3-Rib
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6–Abdominal Structures
The fetal abdomen should be unobstructed and free from compression by limbs or the umbilical cord.
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1-Lungs
2-Stomach in abdomen
3-Rib
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4- Bladder
5- Two umbilical arteries
6- cord insertion
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1-Kidneys
2-Lung
3-Ribs
4-Spine
5-Pelvic bones
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7–Limbs and Extremities
Upper and Lower Limbs: Limbs should be positioned to avoid obscuring critical structures, particularly the abdominal wall, face, and spine.
- Purpose: To assess for limb symmetry and appropriate development.
- Reference Structures: Long bones (humerus, femur), hands, and feet.
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1-Hand and finger
2-Lower arm
3-Upper arm
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1-Upper arm
2-Lower arm
3-Hand with fingers
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1-Foot
2-Lower leg
3-Upper leg
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8–Spine
Spine Alignment: The spine should appear straight or slightly curved, maintaining a natural position without excessive curvature.
- Purpose: Ensures accurate crown-rump length (CRL) measurement and detection of spinal abnormalities.
- Reference Structures: Cervical, thoracic, lumbar, and sacral vertebrae.
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