When will a gestational sac be visible (soonest) on a sonar during early pregnancy?

Gestational sac ?'s: The gestational sac is usually identified at 4-5 weeks of pregnancy (dated from last menstrual period). Sometimes pregnancy occurs at a delayed ovulation, so if the sac is not seen, it may be b/c your ovulation in this cycle was delayed (common at age 38) so obtain a following ultrasound exam in a couple weeks to confirm pregnancy growth, or get serial HCG levels to confirm progression.

5 weeks: Usually by about 5 weeks. Occasionally there may be signs in the 4th week.