Synopsis
Interpret early-pregnancy hCG and ultrasound as complementary time-dependent tests, using validated repeat intervals and avoiding false diagnoses from single thresholds or uncertain dates.
- Transvaginal ultrasound is first-line for early pregnancy location and viability; offer transabdominal ultrasound if it is declined and explain reduced sensitivity and longer repeat intervals.
- Scan the endometrial cavity, both adnexa and pelvis for a gestational sac, yolk sac, embryo, heartbeat, adnexal mass and free fluid; do not stop at an empty uterus.
- Use crown–rump length when an embryo is visible and mean gestational sac diameter when it is not; do not use last menstrual period alone to decide that a heartbeat should be present.
Key red flags
New shoulder-tip pain, collapse, severe unilateral pain or peritonism during serial follow-up requires emergency reassessment regardless of a rising or falling hCG.
Investigation priorities
Establish pregnancy location and developmental features with the highest early-pregnancy resolution.
Management branches
Pain, bleeding or pregnancy uncertainty leads to early-pregnancy ultrasound.
- Obtain informed consent for transvaginal imaging, offer a chaperone and a transabdominal alternative with limitations when internal scanning is unacceptable.
- Assess uterus, cervix, both adnexa and free fluid and document sac, yolk sac, embryo, CRL, mean sac diameter and heartbeat using trained measurements.