ULTRASOUND IN OBSTETRICS (AND GYNECOLOGY) ppt

First Trimester Ultrasound

• Confirmation of Intrauterine Gestation: Confirms pregnancy is occurring in the uterus.
• Fetal Cardiac Activity: Detects fetal heartbeat.
• Identifying Molar Gestations: Detects abnormal pregnancies.
• Identifying Multiple Gestations: Diagnoses multiple pregnancies.
• Screening for Cardiac Defects: Checks for heart problems.
• Screening for Down Syndrome: Screens for Down syndrome using nuchal translucency, nasal bone, and biochemical markers.
• IUP vs. Ectopic: Differentiates between intrauterine and ectopic pregnancies.
• Prognosis of Pregnancy: Assesses the likelihood of a successful pregnancy.
• Number of Fetuses: Determines the number of fetuses.
• Dating the Gestation: Estimates the pregnancy's age.
• Crown-Rump Length (CRL): Used to measure gestational age, within +/- 7 days in first trimester.
• Nuchal Translucency: A widening of the posterior neck area signifies potential chromosomal abnormality.
• Fetal Nasal Bone: Absence of a nasal bone is associated with chromosomal abnormalities.
• Fetal Cardiac Abnormalities: Detailed views of the fetal heart can rule out many potential anomalies.
• Chorionicity: Determines if twins are identical or fraternal using chorion identification.
• Chorionic Villus Sampling (CVS): Ultrasound can guide CVS procedure.
• Molar Gestation: Characterized by "swiss cheese"-like echogenic material in the uterus.

Second Trimester Ultrasound

• Level II Structural Ultrasound: Comprehensive fetal anatomy scan.
• Timing: Typically performed between 16-20 weeks.
• Examined Structures: Brain, spine, face, thorax, heart, stomach, intestines, kidneys, bladder, limbs, placenta, umbilical cord, cervix, and gender determination.
• "Lemon Sign": Suggests potential spinal cord abnormalities (Arnold-Chiari malformation and spina bifida).
• Estimating Gestational Age: Uses various measurements like abdominal circumference, head circumference, biparietal diameter, and femur length.
• Bladder Size: Enlarged bladder may indicate outlet obstruction, while absence may suggest kidney problems (renal agenesis).
• Umbilical Cord Vessels: 2-vessel umbilical cord is present in ~1% of pregnancies, and has a slight correlation with chromosomal abnormalities (~2-5% risk).

Third Trimester Ultrasound

• Assessment of Fetal Well-being: Evaluates fetal health using amniotic fluid index, breathing movements, movements/tone, and Doppler flow studies.
• Amniotic Fluid Index: Evaluates fluid volume, with low levels indicating potential placental problems and high levels indicating possible complications like twin-to-twin transfusion.
• Fetal Breathing Movements: Indicates fetal health.
• Fetal Movements and Tone: Assesses fetal health using biophysical profile.
• Doppler Flow Studies: Assesses blood flow in fetal vessels (i.e., umbilical arteries, middle cerebral artery, and uterine arteries).
• Diagnosis and Management of Malpresentation: Diagnoses and manages abnormal fetal positions (e.g., breech presentation).
• Intrauterine Interventions: Guides interventions, such as fetal transfusions or catheter placements (if needed).
• Placental Grading: Assessment of the placenta (though often considered less crucial compared to other evaluations).
• Assessment of Postpartum Uterus: Evaluates the uterus after delivery.
• Cervical Length: Shortened cervical length is associated with premature labor/delivery.