Findings on ultrasound: mean sac diameter: 2.9 crown to rump length: 0.7 yolk sac: 0.4 heartbeat: not visualized estimated ultrasound age based off of crl is 6 weeks 4 days last period was end of august. is this necessarily a miscarriage?

Fetal heartbeat: About 6 weeks(post 1st day LMP) is the earliest you can see the heartbeat ( which is about where you are now-depending on what day was LMP and when you had the US) . Would consider repeating in 1 week as it should be more visible. Discuss with your Ob. https://www.healthline.com/health/pregnancy/when-can-you-hear-babys-heartbeat#first-ultrasound