US use in obst & gynae

Gestation and Ultrasound Appearance

Early Ultrasound Findings

• The appearance of the intrauterine sac, fetal heartbeat (FH) pulsation, and yolk sac can be detected at various gestational ages, depending on the type of ultrasound scan performed.

Transabdominal Scan vs. Transvaginal Scan

• Gestational age for detection:

  • Transabdominal scan:

    • Intrauterine sac visible at 5.5 weeks

    • Fetal heartbeat (FH) and crown-rump length (CRL) visible at 6 weeks

    • Yolk sac visible at 6 weeks

  • Transvaginal scan:

    • Intrauterine sac visible at 4.5 weeks

    • Fetal heartbeat (FH) and CRL observable at 5 weeks

    • Yolk sac visible at 5 weeks

Measurement Parameters

• Intrauterine Sac:

  • Size ranges from 2-4 mm by 5.5 weeks (transabdominal) and 4.5 weeks (transvaginal)

• Crown-Rump Length (CRL):

  • Typically measures 2-4 mm by 6 weeks (transabdominal) and 5 weeks (transvaginal)

• Yolk Sac:

  • Size must reach around 10 mm by 6 weeks (transabdominal).