CHAPTER 1

Early Pregnancy Ultrasound

From First Principles to Clinical Confidence

Most early pregnancy scans look straightforward — until they are not.

The difference between a missed ectopic and a properly managed pregnancy of unknown location is not luck — it is a systematic, confident approach to ultrasound that you can learn, practise, and master.

This chapter teaches you everything— from probe technique to identifying a ruptured ectopic before it causes a catastrophe.

9

Ectopic Sites Covered

20+

Named Signs & Cut-offs

4

Twin Types Classified

3

GTD Types Explained

TOPICS COVERED IN THIS CHAPTER

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Recognizing the orientation and technique of the probe for transvaginal and transabdominal scanning.

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Identifying a true gestational sac — eccentric location, echogenic ring, and the Double Decidual Sac Sign

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Establishing the sequence of early pregnancy milestones: gestational sac, yolk sac, embryo, and cardiac activity

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Applying the six-point early pregnancy checklist: Presence, Location, Structure, Viability, Number, Dating

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Recognising the critical ultrasound cut-offs for diagnosing failed pregnancy (the 20–25–7 rule)

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Differentiating a true gestational sac from a pseudosac in suspected ectopic gestation

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Identifying all nine sites of ectopic pregnancy and their relative frequency, with emphasis on tubal and interstitial ectopics

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Distinguishing ectopic gestation from corpus luteum cyst using the Bagel Sign, Beak Sign, and Ring of Fire

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Interpreting serial beta-hCG trends to guide clinical decision-making in pregnancy of unknown location

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Assigning chorionicity and amnionicity in multiple gestation using early TVS landmarks (Lambda sign, T-sign)

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Exploring gestational trophoblastic disease — complete and partial mole, theca lutein cysts, and AV shunting in invasive disease

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Reporting subchorionic haemorrhage with clinical grading using circumferential involvement

WHAT YOU WILL WALK AWAY WITH

✔  A systematic checklist approach for every early pregnancy scan — never miss a finding again

✔  Confidence to diagnose ectopic pregnancy, including rare sites like interstitial and scar ectopic

✔  The idea to assign chorionicity and amnionicity accurately on first-trimester twin scans

✔  Clarification of gestational trophoblastic disease and when to escalate

✔  Ready-to-use reporting language and clinical decision pathways for everyday practice