When is fetus visible on ultrasound scan?

Q: During which day / week / month is the fetus large enough to be visible in ultrasound? What no. of days / weeks / months does the fetal heart starts to take shape and when can one hear its beat?

A:By transabdominal scanning the gestational sac can be seen in the uterus by 6 weeks, and fetal echoes and cardiac activity (heart beat) by 7 weeks. These can be seen roughly 1 week earlier by transvaginal scan. One can hear the fetal heart beat by Doppler as early as 10 weeks of pregnancy (usually gynaecologists try this only after 14 weeks), and with an ordinary stethoscope in thin women by 20-24 weeks.